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Title: The Silversmith's Handbook
Containing full instructions for the alloying and working of silver
Author: George E. Gee
Release Date: December 30, 2014 [EBook #47816]
Language: English
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Transcriber Note
Emphasized text is displayed as _Italic_.
Except in tables where the characters ¼ and ½ were used,
whole and fractional numbers are shown like: 36-1/8.
THE
SILVERSMITH'S HANDBOOK
BY THE SAME AUTHOR, UNIFORM WITH THE PRESENT VOLUME.
_Ninth Impression, price 5s. net, cloth._
THE GOLDSMITH'S HANDBOOK,
CONTAINING
FULL INSTRUCTIONS FOR THE ALLOYING AND WORKING OF GOLD.
Including the Art of Alloying, Melting, Reducing, Colouring,
Collecting, and Refining; The Processes of Manipulation, Recovery of
Waste; Chemical and Physical Properties of Gold; with a New System
of Mixing its Alloys, Solders, Enamels, and other Useful Rules and
Recipes.
_Crown 8vo, price 3s. 6d. net, cloth._
THE
HALL-MARKING OF JEWELLERY,
PRACTICALLY CONSIDERED.
Comprising an account of all the different Assay Towns of the United
Kingdom, with the Stamps at present employed; also the Laws relating
to the Standards and Hall Marks at the various Assay Offices; and a
variety of Practical Suggestions concerning the Mixing of Standard
Alloys, and other Useful Information.
CROSBY LOCKWOOD & SON,
7, Stationers' Hall Court, Ludgate Hill, E.C.
THE
SILVERSMITH'S HANDBOOK
CONTAINING
FULL INSTRUCTIONS
FOR THE
_ALLOYING AND WORKING OF SILVER_
INCLUDING THE DIFFERENT MODES OF REFINING AND MELTING
THE METAL; ITS SOLDERS; THE PREPARATION OF IMITATION
ALLOYS; METHODS OF MANIPULATION; PREVENTION OF
WASTE; INSTRUCTIONS FOR IMPROVING AND
FINISHING THE SURFACE OF THE WORK
TOGETHER WITH OTHER USEFUL
INFORMATION AND MEMORANDA
By GEORGE E. GEE
GOLDSMITH AND SILVERSMITH
AUTHOR OF "THE GOLDSMITH'S HANDBOOK," "THE HALL-MARKING OF JEWELLERY,"
ETC. ETC.
Fifth Edition
[Illustration]
LONDON
CROSBY LOCKWOOD AND SON
7, STATIONERS' HALL COURT, LUDGATE HILL
1921
PRINTED BY
WILLIAM CLOWES AND SONS, LIMITED,
LONDON AND BECCLES.
PREFACE.
The object of this Treatise is to supply a want long felt in the Silver
Trade, namely, a work of reference from which workmen, apprentices,
and manufacturers, employing the material upon which it treats, may
find information which will be of assistance to them in the performance
of their daily duties, and by which their operations may be rendered
more successful. The Author was led to undertake the present work
from having had many opportunities, during his lengthened experience
in the art of silver-working, of observing the difficulties and
stumbling-blocks that are constantly to be met with in the manifold
branches of this important trade, by those _practically_ engaged in it,
and also by those persons who are desirous of acquiring a _thorough_
knowledge of the mechanical and manipulative details belonging to it.
To assist his object, numerous illustrations have been prepared for
this Treatise, with the view of rendering the various processes of the
art more readily comprehensible, and to save a lengthened or detailed
description of them.
The different modes of alloying and melting silver; its solders; the
preparation of imitation alloys; methods of working; the prevention
of waste; instructions for improving and finishing the surface of the
work, together with other useful information and memoranda--all these
have been carefully collected and placed in order in the body of the
work.
The Author has endeavoured, throughout, to present the contents (which
he has with some little difficulty and labour brought together) in
as practical and readable a form as is compatible with accuracy and
efficiency.
G. E. GEE.
PREFACE TO THE SECOND EDITION.
Since the publication of the first edition of this work important
changes have taken place in the commercial value of silver, its
present cost in the best markets being sixpence per ounce lower than
it was when this volume first appeared in 1877. This depreciation in
value has, of course, necessitated a thorough revision of the former
prices of the various alloys, solders, and other substances mentioned
throughout the work; and this has been done in order to render it the
more complete as a work of general reference, conveying correct and
useful information to the reader. The Author trusts that his endeavours
in this direction will be appreciated.
58, Tenby St. North, Birmingham.
_February, 1885_.
PREFACE TO THE FOURTH EDITION.
In issuing the present edition, a few introductory remarks are
necessary to explain that numerous revisions have been made in Chapters
VI. and VII. (by means of the Tables referred to below) regarding the
cost prices of the different alloys, solders, etc., which I trust will
increase the value of the book.
Through the repeal of the silver duty in the year 1890, a great
impetus has been given to the Silver industry of this country, and
notwithstanding the length of time that has elapsed since this book was
first published, a steady demand has continued for its possession by
workers in the precious metal trades--a fact which is gratifying to the
Author, not only because a reprint is again called for, but as showing
that the work has held its position, and may now justly claim to be a
standard authority on the subject of which it treats.
It has not been found necessary to interfere with the general
processes embodied in the book, as they are practically the same as
formerly; but as regards the commercial value of silver, there is
again a considerable depreciation[A] to record on the prices prepared
for the second edition in 1885, and it becomes imperative that this
depreciation should be dealt with in this new edition, in order to
bring the work up to date.
[A]
_s._ _d._
In 1877 fine silver cost 5 2 per ounce.
" 1885 " " 4 8 "
" 1906 " " 3 0 "
The market price of silver has for many years been of a very variable
nature, almost each day's prices showing a difference, so that it would
be impossible to provide the reader with an unvarying fixed price per
ounce. The best and most practical thing to do under the circumstances,
it seemed, was to carefully revise the different cost prices of the
alloys and solders specified in Chapters VI. and VII. and give them by
way of approximate Tables, compiled for each chapter separately. These
two Tables follow this Preface (making pp. ix. and x.) and will serve
as a ready reference for present workers in the silver trades. Thus,
by bringing the figures down to date, the work may still retain its
reliable character as a practical guide to the silversmith's workshop.
G. E. GEE.
58, Tenby St. North, Birmingham.
_January, 1907._
PUBLISHERS' NOTE TO FIFTH EDITION.
In February 1921 silver was quoted at 34-1/2_d._ to 36-1/8_d._, and it
is therefore sufficient to note that the prices at that date correspond
approximately to those current in 1907. It should be noted that the
melting of British gold and silver is prohibited, as well as their
export.
Table of Revised and Up-to-date Cost Prices of the Different Alloys in
Chapter VI.
+-----+----------------------+-------------------+---------------------+
|Page.| No. and quality of | Cost price 1885. | Cost price 1907 |
| | alloy. | | and 1921. |
+-----+----------------------+-------------------+---------------------+
| 61 | Old standard alloy | _For_ 4/4 per oz. | _read_ 2/9½ per oz.|
| 62 | New standard alloy | " 4/6 " | " 2/10½ " |
| 64 | No. 1, silver alloy | " 4/2 " | " 2/9 " |
| 64 | No. 2, silver alloy | " 3/9 " | " 2/5½ " |
| 65 | No. 3, silver alloy | " 3/6 " | " 2/3½ " |
| 65 | No. 4, silver alloy | " 3/3 " | " 2/1½ " |
| 66 | No. 5, silver alloy | " 3/2 " | " 2/0½ " |
| 66 | No. 6, silver alloy | " 3/1 " | " 2/- " |
| 67 | No. 7, silver alloy | " 3/- " | " 1/11 " |
| 67 | No. 8, silver alloy | " 2/10 " | " 1/10 " |
| 70 | French coinage alloy | " 4/2 " | " 2/9 " |
| 70 | French plate alloy | " 4/5 " | " 2/10 " |
| 70 | French 0·800 alloy | " 3/9 " | " 2/5½ " |
| 72 | German coinage alloy | 0·900 standard | " 2/9 " |
| 72 | German silver wares | | |
| | alloy | 0·950 1st standard| " 2/10¼ " |
| 73 | Ditto | 0·800 2nd " | " 2/5½ " |
| 73 | Ditto | 0·750 3rd " | " 2/3½ " |
+-----+----------------------+-------------------+---------------------+
This Table is based on the market price of fine silver being 3/- per
ounce.
Table of Revised and Up-to-date Cost Prices of the Different Solders in
Chapter VII.
+-----+---------------------------+-----------------+-------------------+
|Page.| Quality of solder. |Cost price 1885. | Cost price 1907 |
| | | | and 1921. |
+-----+---------------------------+-----------------+-------------------+
| 78 |Hardest silver solder |_For_ 3/9 per oz.|_read_ 2/5½ per oz.|
| 79 |Hard silver solder | " 3/6 " | " 2/3½ " |
| 79 |Easy silver solder | " 3/2 " | " 2/0½ " |
| 81 |Best silver solder | " 3/9 " | " 2/5½ " |
| 82 |Medium silver solder | " 3/6 " | " 2/3½ " |
| 82 |Easy silver solder | " 3/3 " | " 2/1½ " |
| 83 |Common silver solder | " 3/- " | " 1/11 " |
| 84 |Enamelling silver solder | " 3/9 " | " 2/5½ " |
| 84 | Ditto | " 3/2 " | " 2/0½ " |
| 84 |Filigree solder | " 3/9 " | " 2/5½ " |
| 85 |Quick-running silver solder| " 3/- " | " 1/11 " |
| 85 |Silver solder for chains | " 3/- " | " 1/11 " |
| 85 |Easy solder for chains | " 3/- " | " 1/11 " |
| 85 |Common silver solder | " 2/9 " | " 1/9 " |
| 86 |Common easy solder | " 2/9 " | " 1/9 " |
| 86 |Arsenic silver solder | " 3/9 " | " 2/5½ " |
| 86 | Ditto | " 3/6 " | " 2/3½ " |
| 86 |Easy silver solder | " 3/2 " | " 2/0½ " |
| 87 |Common easy silver solder | " 2/9 " | " 1/9 " |
+-----+---------------------------+-----------------+-------------------+
This Table is based on the market price of fine silver being 3/- per
ounce.
CONTENTS.
INTRODUCTORY CHAPTER.
Page
Silver a Precious Metal 1
Economy of Treatment 1
Working Silversmiths 2
English and Foreign Workmen 2
Technical Education 2
Pure Silver 3
Plate and Ornamental Wares 4
CHAPTER I.
_Silver._
Silver, Characteristics of 5
Silver for Filigree Work 5
Indian Filigree Workers 5
Malleability of Silver 6
Ductility of Silver 6
Test for Pure Silver 6
Silver known to the Ancients 6
Silver Currency 6
Polished Silver 7
Tarnishing of Silver 7
Density of Silver 7
Fusibility of Silver 7
Heating Power of Silver 7
Action of Silver under Great Heat 8
Hardness of Silver 8
Nitrate of Silver 8
Silver resists Aqua-regia 8
Chief Places of Filigree Manufacture 8
Chief Uses of Silver 9
Price of Silver, Commercial 9
Ores of Silver 9
Dissolution of Silver 9
Caustic Alkalies 10
Nitre 10
Vegetable Acids 10
CHAPTER II.
_Sources of Silver._
Silver-mining 11
Great Britain 11
British Isles' Yield of Silver 11
Spain 11
America 11
Native Silver 11
European Supplies of Silver 12
American Supply of Silver 12
The Richest Mine 12
State of the Jewellery Trade 12
Yield of Silver 13
Foreign Silver Currency 13
Chief Sources of British Silver 13
State in which it is found 14
CHAPTER III.
_The Assay of Silver Ores._
Silver and Mercury 15
Assaying of Silver Ores 16
Crucible Assay 16
Fluxes for Crucible Assay 16
Assay of Genuine Silver Ores 16
Carbonate of Soda 16
Dimensions of Crucible 16
Litharge 17
Preparation and Charge for Assay 17
Treatment in the Furnace 18
Casting-mould 18
Scorification Process 18
Fusing Cup or Scorifier 19
Special Form of Scorifier 19
Scorification Assay the Reverse of Crucible Assay 19
Charge for Scorification Assay 20
Advantages of the Process 20
Anthracite and its Object 21
Separation of the Silver from the Slag 21
Borax, use of, in Assaying 22
Continental Method of Assaying 22
Flux and Charge for Crucible 23
Details of the Process 23, 24
Skittle-pot 25
Cupellation 26
Cupel, its Mode of Manufacture 26
Cupel-mould 27
Assayer's Muffle 28
Cupel-tongs 28
Brightening 29
Sprouting 29
Weighing of Silver Assay 30
Chief Alloy of Silver 30
CHAPTER IV.
_The Cupellation of Silver Ores._
Test-ring 31
Preparation of Bone-ash 32
Defects in Bone-ash Cupel 33
Currents of Air to the Furnace 33
Withdrawal of the Silver from the Cupel 34
Removal of the Litharge, Manner of 35
Quantity of Alloy per Cupel 35
Purity of Silver after Cupellation 37
Ancient Method of Assaying 37
Dr. Lamborn on Assaying 38
Scriptural Testimony 37, 38
English System of Assay 39
CHAPTER V.
_The Alloys of Silver._
Silversmith's Alloys 40
Filigree Work 40
Alloy 41
Amalgam 41
Metals employed in the Industrial Arts 41
Metals, their various Characteristics 41
Principal Alloys of Silver 42
Copper 42
Characteristics of Copper 43
Protoxide of Copper 44
Action of Acids on Copper 44
Bean-shot Copper for Alloying 44
Chemical name for Copper 44
Nickel 45
Cronstedt 45
Density of Nickel 45
Ductility of Nickel 45
Malleability of Nickel 45
Fusibility of Nickel 45
Nickel Coinage 45
Nickel Alloys 46
Electro-plate 46
Zinc 46
Spelter 46
Zinc in Silver Solder 46
Annealing of Zinc 47
Specific Gravity of Zinc 47
Spelter used by Jewellers 47
Tarnishing of Zinc 47
Malleability of Zinc 48
Ductility of Zinc 48
Tenacity of Zinc 48
Tin 48
Ancient Workers in Tin 48
Density of Tin 48
Christianity and Tin 48
Fusibility of Tin 48
Dissolving of Tin 48
Tin alloyed with Gold 49
Tin alloyed with Silver 49
Tin in Silversmith's Solders 49
Vapours of Tin injurious to Gold 49
Malleability of Tin 49
Ductility of Tin 49
Tenacity of Tin 49
Scientific Name for Tin 50
Table of Metallic Elements 50
Melting-points of the Principal Metals 51
Physical Properties of the Principal Metals 51
CHAPTER VI.
_Various Qualities of Silver._
Mechanical Uses of Silver 52
Filigree Work 52
Birmingham 52
London 52
Indian 53
Chief Places of Filigree Manufacture 53
Continental Cheap Labour 54
Hand-made Articles 54
Process of Workmanship 55
Maltese Filigree 55
Chinese and Japanese Filigree 56
Filigree of Norway and Sweden 56
Filigree working, Necessity for Pure Metal 56
Old Method of making Filigree 57
Twisting of the Wire 58
Lathe, Use of 58
Flattening of Twisted Wire for Filigree 59
New Method of preparing Filigree Wire 59
English Standards for Silver 60
English Coinage 61
Standard Silver Alloy 61
Alloy for Hall-marking 62
Standard Alloy of the Highest Quality 62
Standard Alloy for Hall-marking 62
Alloy commonly used in England 63
Qualities used by English Silversmiths 63
Drawbacks to Hall-marking 63
Method of calculating the Qualities of Silver 63
Silver Alloy No. 1, cost 4_s._ 7_d._ per oz. 64
" No. 1, differently calculated 64
" No. 2, cost 4_s._ 1_d._ per oz. 64
" No. 2, differently calculated 64
" No. 3, cost 3_s._ 10_d._ per oz. 65
" No. 3, differently calculated 65
Silver Alloy No. 4, cost 3_s._ 7_d._ per oz. 65
" No. 4, differently calculated 65
" No. 5, cost 3_s._ 6_d._ per oz. 66
" No. 5, differently calculated 66
" No. 6, cost 3_s._ 3_d._ per oz. 66
" No. 6, differently calculated 66
" No. 7, cost 3_s._ 2_d._ per oz. 67
" No. 7, differently calculated 67
" No. 8, cost 3_s._ per oz. 67
" No. 8, differently calculated 67
Instructions in the Preparation of Alloys 68
Copper for Alloying 68
French Standards 69
Silver Ware 69
Coinage 69
French Alloy for Coinage 70
French Alloy for Plate 70
French Alloy for Silver Ware 70
Instructions in the Preparation of these Alloys 70
German Standards 71
Silver Ware 71
Coinage 71
Silver Alloy for the German Coinage 72
Alloy for Plate 72
Alloys for Silver Wares 72, 73
Law on the Manufacture of Silver Wares 73
Remedy allowed in Fineness 73
Government Exports 73
Guarantee Marks 73
CHAPTER VII.
_Silver Solders: their Uses and Applications._
The Act of Soldering 74
Cause of Inferior Manufactures 74
Tin in Solders 75
Filed Solders 76
Zinc in Silver Solder 76
Solders made with Copper and Silver 76
Hard Silver Solders 77
Medium Solders 77
Easy Solders 77
Connections for Soldering 77
Flux for Soldering 77
Fusibility of Silver Solders 78
Hardest Silver Solder, cost 4_s._ 1_d._ per oz. 78
Ditto, differently calculated 79
Medium Silver Solder, cost 3_s._ 10_d._ per oz. 79
Ditto, differently calculated 79
Easy Silver Solder, cost 3_s._ 5_d._ per oz. 79
Ditto, differently calculated 80
Remarks on Silver Solders 80
Composition for Solder 81
Best Hard Solder, cost 4_s._ 1_d._ per oz. 81
Ditto, differently calculated 81
Medium Solder, cost 3_s._ 10_d._ per oz. 82
Ditto, differently calculated 82
Easy Solder, cost 3_s._ 7_d._ per oz. 82
Ditto, differently calculated 82
Common Solder, cost 3_s._ 3_d._ per oz. 83
Ditto, differently calculated 83
Directions on the Melting of Solders 83
Solder for Enamelling, cost 4_s._ 1_d._ per oz. 84
" " cost 3_s._ 6_d._ per oz. 84
Easy Solder for Filigree Work 84
Quick Running Solder, cost 3_s._ 3_d._ per oz. 85
Silver Solder for Chains, cost 3_s._ 3_d._ per oz. 85
Easy Solder for Chains, cost 3_s._ 3_d._ per oz. 85
Common Silver Solder, cost 3_s._ per oz. 85
Common Easy Solder, cost 3_s._ per oz. 86
Arsenic Solder, cost 4_s._ 1_d._ per oz. 86
Silver Solder with Arsenic, 3_s._ 10_d._ per oz. 86
Easy Silver Solder, cost 3_s._ 6_d._ per oz. 86
Common Easy Solder, cost 3_s._ per oz. 87
Another Common Solder 87
Very Common Solder 87
Directions in the Preparation of Solders 87
Drossy Solders 88
Mode of Soldering Gold and Silver 88
Pallion Solder 88
Blowpipes 89
Solder-dish and Charger 89
Soft Solder 90
Art in Soldering 90
Solder for Filigree 91
Lemaille Solder 91
English Filigree Workers 91
Sprinkle Borax 92
Special Soldering Flux 92
Boiling-out Pickle 93
CHAPTER VIII.
_On the Melting of Silver._
Directions on Melting 94
Weighing Metal for the Crucible 94
Crucibles 95
Best Crucibles to employ 95
Fluxes: their Action on Crucibles 96
Fluxes employed in Melting 96
Testing the Soundness of a Crucible 97
Mixing various Metals for melting 97
Zinc a fusible Metal 98
Charcoal 99
Bad working Material 99
Plumbago Crucible for Melting 99
Tongs for Melting 100
Ingot-mould 100
Flux and the Pouring of Molten Metal 101
Protoxide of Zinc 102
Scrap Silver 102
Carbonate of Soda 102
Dissolving Impurities 103
Lead and Tin in Silver 103
Sal-ammoniac 103
Lemel 103
Mixture prepared for Crucible 104
Burning of Lemel 104
Skittle-pot for Lemel 104
Melting of Lemel 105
Another Mode of melting Lemel 106
Crucible for Lemel 106
Pouring of Lemel from Crucible 107
CHAPTER IX.
_On the Working of Silver._
Rolling Silver 108
Annealing Silver 109
Irregularities in Rolling-mills 110
Messrs Kemp's Mill 110, 111
Table of the Cost of Silver-rolling 112
Slitting Rollers 112
Breaking-down Rollers 112
Wire-rolling 113
Wire-drawing 113
Draw-plate 114
Draw-bench 110, 115
Draw-tongs 115
Drum used by Wire-drawers 115
Fine Wire-drawing 115, 116
Wire-drawer's Punch and Hammer 117
Wrought Work 118
Sparrow-hawk 119
Raised Work 120
Cement for Chasers 121
Snarling-tools for Raising 122
Art in the Silver Trade 123
Burnished Silver Work 124
Silver Filigree Work 125
Stamped or Struck-up Work 126
Press 127
Plain Solid Work 127
Chain Bracelets 128
Present State of Silver Trade 128
Silver, Liability to become tarnished 129
Enamelling 129
Galvanic Ring 129
Mode of preparing Ring 129, 130
Hollow Silver Work 131
Stamping-press 132
Spinning 134, 135
Polishing 135
Water-of-Ayr Stone 136
Polishing-lathe 137
Washing-out Mixture 138
CHAPTER X.
_Enriching the Surfaces of Silver._
Production of the best and richest Surface 139
Oldest Method for Whitening 140
East Indian Silversmiths 141
Indian Mode of Whitening Silver 142
Another Mode of Whitening 142
Boiling-out Pan 143
Boiling-out Mixture 143, 144
Our Mode of Whitening 145
Surface Refining of Silver 146
Brown Colour on Silver Goods 146
Common Articles of Silver 147
Whitening Powder or Mixtures 147
Nitrate of Silver Mixture 148
Improving the Colour of Electro-plate 149
Electro-plating 149
Discoverer of Electro-plating 149, 150
Constant Battery 150
Best Battery for Plating 151
Strength of Battery Solution 151
Bunsen's Battery 152
Exciting Mixture for Battery 152
Zinc Amalgamation 153
Conducting Wires 154
Preparation of Plating Solution 155
Cyanide Solution 156
Black Cyanide 157
Strength of Plating Solution 157, 158
Inferior Plating Solution 159
Recovery of Silver from Plating Solutions 160
Scratch-brushing 161
Scratch-brush Lathe 161
Burnishing Silver Work 161, 162
Oxidizing Silver Work 163
Solution No 1. 163
Solution No 2. 164
Solution No 3. 164
Producing various Shades 165
CHAPTER XI.
_Imitation Silver Alloys._
Melting Imitation Alloys 166
Common Silver Alloy 167
Another 167
Another 168
Another 168
Another 168
Another 168
Another 169
Another 169
Another 169
Another 169
Another 170
Another 170
Chinese Silver 170
Imitation Silver 170
Another 171
Another 171
Another 171
Another 171
White Alloy 172
Clark's Patent Alloy 172
White Alloy 172
Alloy with Platinum 172
Alloy with Palladium 173
Uses for Imitation Alloys 173
Characteristics of Imitation Alloys 174
CHAPTER XII.
_Economical Process._
Working Loss 175
Lowest Estimate Real Loss 175
Total Working Loss 176
Shop Floors 177
Waste-saving Precautions 177, 178
Treatment of Waste 178
Burning of Polishings 179
Treatment of Waste Liquids 180
Processes for the Recovery of Silver from Waste Waters 180, 182
Chloride of Silver 183
Aqua-regia 183
Precipitating Silver in Waste Waters 183
Solution for Precipitation 184
Sediment in Collecting-vessels 185
CHAPTER XIII.
_Licences and Duties._
Acts of the Legislature 186
43 George III., c. 69 186
6 George I., c. 11 187
31 George II., c. 32 188
32 George II., c. 14 188
24 George III., c. 53 188
37 George III., c. 90 188
44 George III., c. 98 189
55 George III., c. 185 189
Table of Various Duties 189
Manufactured Plate 190
Remarks on the Licence Question 191, 196
Act of Parliament in Licences 193
Clause of Act 193, 194
Tax or Licence unjustly Assessed 195, 196
CHAPTER XIV.
_Useful Information for the Trade._
Silversmith's Alloys 197
Silver Wares 197
Cleaning Plate 198
Imitation Silver 198
Another 198
Removing Gold from Silver Articles 198
Oxidizing Silver 198
Dipping Mixture 199
Silver Powder for Copper 199
Powder for Silver 200
To protect the Polish of Metals 200
Silver-stripping Mixture 200
Stripping Silver 201
Soft Solder 201
Soldering Fluid 201
Dissolving Silver 202
Dissolving Silver Alloy 202
Dissolving Copper 202
Dissolving Soft Solder 202
Dissolving Silver Solder 202
Dissolving Sealing-wax 202
Resist Varnish 202
Plate Powder 202
Electro-plating Soft Solder 202
Another Recipe 203
Testing Silver Wares 203
Another Test 204
Perchloride of Iron 205
Aluminium Alloy 205
New Alloy 205
Removing Gold from Silver Wares 205
Silver Plating Fluid 206
Plate-cleaning Powder 206
Solder for Aluminium 206
CHAPTER XV.
Foreign Silver Standards 207
French Work, Duty on 208
Continental Silversmiths 209
French Style of Work 209
German Style of Work 210
Indian Style of Work 210
Austrian Style of Work 211
English Style of Work 211
Index 212
THE
SILVERSMITH'S HANDBOOK.
INTRODUCTORY CHAPTER.
In reviewing the rise and progress of the silversmith's beautiful and
interesting art, in its relation to the manufacture of articles of
personal ornament and luxury at home and abroad, we may observe at the
outset, that the material of which they are composed differs widely
in character from that employed by the ordinary "metalsmiths" and the
manufacturer of "electro-plated wares." Silver, the material of which
we are now treating, being a precious metal and of considerable value,
it is essentially necessary that the most careful means be exercised in
dealing with it from the commencement--that is, from the pure or fine
state--and also that the utmost economy be observed in reference to the
kind of mechanical treatment to which it is subjected in the production
of the silversmith's work, in order to prevent too great a quantity of
waste or loss of material. For it should be borne in mind that silver,
like gold, begins to lose, in one way or another, every time it is
touched; therefore, carefulness and economy will be the characteristics
of our teaching, so far as regards the present subject.
The vast majority of working silversmiths know very little of the
physical and chemical properties of the metal they employ, and still
less of the comparison it bears with other metals in the field of
science; and this want of scientific knowledge is nowhere more apparent
than in our own country, where the English workman, in art education,
is much behind the foreigner; and yet we have some of the finest and
best workmen, in their _special_ branches, in the whole world. The
English workman believes that if the work is worth doing at all, it
is worth doing well; and we have no hesitation in saying, that, if a
good technical education were afforded, concerning the precious metal
trades, he would scarcely have an equal, and certainly no superior,
abroad, in art workmanship, both in respect to the display of good
taste and judgment, combined with a knowledge of design, so far as
the exercise of these qualities is compatible with the manufacture of
articles specially designed for use and ornament.
The object of the information we are about to supply is to enable
the practical silversmith to become a perfect master of his art or
profession; and such a condition, when once achieved, will be found
of considerable assistance to him in the various kinds of manufacture
that present themselves; so that he will know how to begin a piece of
work and when to leave it off; be able to remedy a defect in the metal
when required, as well as be in a position to form an opinion as to the
relative treatment of its different alloys; all of which invariably
require different treatment.
We shall commence by describing the characteristics of _fine silver_,
carefully narrating the distinctive features of its alloys; then
give an account of the processes employed, mechanical and chemical,
in the silversmith's workshop; and conclude by pointing out the
difference between English and foreign work in regard both to style and
workmanship.
It may be thought by the reader, if uninitiated in the art, that
the costly plate and other articles made from the precious metal
are manufactured from entirely _pure_ silver, and therefore that
they possess absolute freedom from alloy; but this is not the case.
Pure silver being far too soft to stand the necessary wear and tear
of (metallic) life, it is mixed with some other metal, to give it
increased hardness. In the manufacture of plate and ornamental wares
the metal employed is always copper, in various proportions, thus
forming different commercial qualities; and of these we shall speak
hereafter. Our first object is to treat of the chemical and physical
properties of the pure metal.
CHAPTER I.
Silver.
Pure silver is, next to gold, the finest metal, but of a smoother and
more polished nature. It may be said to be almost infinitely malleable,
but it will not so easily yield or extend under the hammer as fine
gold. As a malleable metal, however, it stands next to it in this
respect. It is characterized by its perfectly white colour, being the
whitest of all the metals. It is harder than gold, yet in a pure state
it is so soft that it can easily be cut with a knife. On account of its
extreme softness, when in a pure state, it is employed for filigree
work, being utterly devoid of that elastic power which is found in the
metal when alloyed. It is for this reason that the Indian filigree
workers, who are the finest in the world, are so very particular about
the absolute purity of the metal before commencing the manufacture of
their artistic work; all of which is exceedingly beautiful.
It is reported that fine silver is capable of being beaten into leaves
of less than one-hundred-thousandth part of an inch in thickness.
For the accuracy of this statement we cannot vouch, never having had
occasion to try the experiment; its employment in that form being
unknown in the ordinary industrial pursuits. Fine silver is extremely
ductile, and may be drawn into the very finest wire without breaking,
and almost without annealing. Its purity can be partly ascertained by
the latter process; for perfectly fine silver never changes colour by
heat, whereas when it contains alloy it blackens if heated in contact
with a current of air, and soon hardens in wire-drawing.
Silver was a metallic element known to the ancients, and it is
repeatedly mentioned in the Holy Scriptures. In the time of the
patriarchs we read of it as having been constantly employed in the
transactions of nations, and that it was in use as a standard of value;
thus forming a circulating medium for the purpose of exchange. This
function it has always continued to fulfil down to the present day,
except that since the year 1816 it has not been so employed in the
English currency. However, as token money, it is everywhere recognised
as a circulating medium of trade. The Egyptian symbol for silver was
represented by Fig. 1, relating to the moon; in modern chemistry it is
understood by _ag._ from the Latin name _argentum_, denoting silver.
[Illustration: _Luna._ Fig. 1.
Egyptian mark for Silver.]
Fine silver is capable of receiving a polish scarcely inferior in
lustre to that of highly polished steel, and in this state it reflects
more light and heat than any other metal, without any perceptible
change of colour for some considerable time. It is chiefly on this
account, as well as its resistance to oxidation in air and water, that
it is used for such a variety of purposes, not only of ornament and
luxury, but also in a domestic way. Silver, unlike gold, cannot resist
the influence of sulphuretted hydrogen, from the action of which it
very soon becomes much tarnished if left exposed in damp rooms, &c.
Silver ranks next to gold in point of ductility and malleability.
When pure, its density, or specific gravity, lies between 10.47 and
10.50, taking water as 1, according to the degree of compression it
has received by rolling and hammering. It is fusible at a full red
heat, or about 1873° Fahr. It is a metal having a very low radiating
power for heat; hence silver wire of given dimensions retains and
conducts heat better than a similar piece of another metal; for the
same reason, a liquid contained in a silver vessel retains its heat
much longer than if placed in one made of some other substance. Silver
volatilises when subjected to a very great temperature in the fire,
emitting rather greenish fumes. It loses between 2/21sts and 3/25ths,
in proportion to its impurity, of its absolute weight in air when
weighed in water. In point of tenacity it occupies the fifth position
among the useful metals. In hardness it lies between copper and gold;
and a small addition of the former substance considerably increases
this quality, in which state it is largely employed in the arts. Nitric
acid is the proper solvent for silver, as it dissolves it with the
greatest ease and rapidity, forming _nitrate_ of silver, which is much
used for medical purposes, and in art. Sulphuric and hydrochloric acids
act upon it but slowly in the cold. Silver resists partially the best
aqua-regia, probably on account of the dense chloride which forms on
the surface of the metal, from the action of the hydrochloric acid in
the mixture of aqua-regia.
Fine silver is largely used in the industrial and commercial arts,
in the manufacture of silver lace and fine filigree work; the latter
branch being more commonly practised in India, Sweden, Norway, and
some parts of Germany, where labour is cheap, than in England. This
class of silversmith's work takes a long time to produce, and as
labour forms the chief item of its cost, this, not unnaturally, acts
as a great drawback in the extension of the art of very fine filigree
working, in all its intricate variety, in countries where labour is
dear. To this subject we shall subsequently refer again in detail.
Fine silver, with a small proportion of alloy, is largely used by all
nations for purposes of coinage. It amalgamates with nearly all the
metals, but is principally used in alloys suitable to the watchmaker's
and silversmith's art. The purchasable price of fine silver for
manufacturing purposes, which in 1884 was 4_s._ 8_d._ is now, 1921,
3_s._ per ounce, troy weight, varying however in value according to the
total amounts purchased; for which see refiners' and assayers' charge
lists, to be procured at the offices of any bullion dealer. The silver
ores of commerce have generally an intermixture of a small quantity
of gold, and sometimes instances have occurred in which it has been
employed in manufactures without a proper chemical investigation; and
in such cases the loss resulting from the omission would have amply
paid the expenses of the process.
Exposed to the action of hot and concentrated sulphuric acid, silver
dissolves, setting free sulphurous acid. By the application of this
process--which is one of the most advantageous methods--silver may
readily be separated from gold, sulphuric acid having no action upon
the latter metal. With the exception of gold, silver perhaps more
perfectly resists the action of the _caustic alkalies_ and the powerful
effects of _nitre_ (saltpetre) than any other metal, if we omit
platinum from the list of elements at present known to metallurgical
chemistry. For reasons such as these its superiority for the
manufacture of utensils for culinary and other domestic purposes is at
once apparent, and because it is a metal upon which _vegetable acids_
produce no effect.
CHAPTER II.
Sources of Silver.
Strictly speaking, silver mining does not exist as a distinct operation
in Great Britain, for it can hardly be said that this country possesses
any great quantity of silver ore. Yet we must not disguise or leave
unnoticed, in dealing with this subject, the positive fact that silver
is found to some extent in our copper and lead mines, principally
in the latter; but in no case, as far as we know, have mines been
worked for the sake of the silver alone. It is almost always found
in conjunction with lead, and it is from that source that we have a
good supply of British silver. The average annual yield in the British
Isles for some years has been equal to 800,000 ounces--a position in
regard to the quantity produced ranking second only to Spain amongst
the nations of the world, America, of course, being excepted. Silver is
found in a native state, the commonest ore being a sulphuret.
The chief European supplies are derived from Spain, in which country
genuine silver ore exists; from Saxony and Prussia, where the ores are
principally associated with lead, as in England; and from Austria,
where it is for the greater part found mixed with copper. Silver is
nearly always to be found in copper and lead mines, but generally in
such small quantities that it is rarely worth the trouble and expense
of separation.
Considerably more than three-fourths of the whole total supply of
silver comes from America; and in fact nearly the whole territory of
America is said to be more or less argentiferous. Until lately Mexico
carried off the palm, as containing and yielding the largest percentage
of silver; but through the discovery of another mine in the United
States, at Nevada, of considerable richness, which has yielded enormous
supplies, we shall not be far wrong in pronouncing the silver mines in
the State of Nevada to be the richest in the whole world. The extensive
production of these mines, combined with other causes, has led to a
considerable depreciation in the value of silver, and probably this may
yet lead to its more extensive employment in the arts and manufactures;
and, in the midst of the very general depression of the jewellery
trade, any change extending in that direction would be joyfully
accepted by the thousands of workmen in the precious metal trades now
standing idle. We are told that, since the year 1860, the production of
silver has increased from an average yield of eight or nine to fourteen
millions per annum, or about 60 per cent.; while, on the other hand,
the foreign demand for the metal (formerly largely employed for the
currency) has greatly diminished. The rise in cost of silver during the
war years and those immediately following necessitated an Act in Great
Britain "to amend the law in respect of the standard fineness of silver
coins current in the United Kingdom and in other parts of His Majesty's
Dominions."
The chief sources of supply in the British Isles, according to
Professor George Gladstone, are as given below; and as all the silver
found in this country is produced from lead ores, the average yield
here given must be understood to exist in about that proportion to
every ton of lead ore assayed:--Isle of Man, 50 to 60 oz.; Cornwall,
about 30 oz.; Devonshire, about 30 oz.; Cardiganshire, 15 to 20 oz.;
Montgomeryshire, 15 to 20 oz. Thus, it will be seen the lead ores of
the Isle of Man yield the greatest proportion of silver in the British
dominions. Silver is also found in the undermentioned counties, in
all of which it is produced from lead ore:--Cumberland, Durham, and
Northumberland, Denbighshire, Flintshire, and Derbyshire; but the
percentage is much smaller than in the preceding cases. Ireland also
yields a fair percentage of silver.
CHAPTER III.
The Assay of Silver Ores.
A large proportion of the silver of commerce is extracted from ores
(which are too poor to allow of their being smelted or fused) by a
process called amalgamation. Founded on the ready solubility of silver,
&c., in metallic mercury, the ore is first crushed to powder, then
mixed with common salt, and afterwards roasted. By the adoption of this
plan the silver is reduced to a state of chloride. The roasting is
done in a reverberatory furnace, in which the heat is very gradually
raised, the ore being constantly stirred; the heat is then increased
sufficiently to raise the ore to a good red heat. It is then put into
wooden barrels, revolving on iron axles attached to the ends, and
scraps of iron are then added to it; both are then agitated together by
rotary motion, the effect of which is to reduce the chloride of silver
to a metallic state. When this is effected, it is again agitated with
mercury, and a fluid amalgam is formed with the metal, together with
any other metallic ingredient that may happen to be present in the
roasted ore. Subsequently, to recover the silver, the mercury is driven
off by heat, and the silver is thus left behind in an impure state.
There are three ways of assaying silver ores; they are in the _test_
assay as follows:--
1. Melting in a crucible.
2. Scorification.
3. Cupellation.
In the crucible assay the ore is commonly run down with a suitable
flux, those most frequently employed being litharge, carbonate of soda,
borax, and charcoal. These four substances are all that are required by
the practical assayer in the treatment of the regular ores of silver.
[Illustration: Fig. 2. Fire-clay Crucible.]
The assaying of the genuine ores is performed in the following manner;
that is, if they contain but little earthy matter. They may then be
conveniently treated by fusing with carbonate of soda, on account
of its cheapness, and borax, in a fire-clay crucible (Fig. 2). The
dimensions of the crucible should be as follows: 4-1/2 inches in
height, and 2-1/2 inches in its greatest diameter, which should be
at the top. A quantity of litharge (a semi-vitrious substance, oxide
of lead), more than is actually necessary to take up the whole of
the silver in the ore, should be added, so as to promote fusion, and
collect the ingredients into one mass at the bottom of the crucible.
In preparing the ore for the crucible, it must be well pounded, and
intimately mixed with the undermentioned chemicals:--
Pounded silver ore 240 grains.
Litharge 800 "
Carbonate of soda 700 "
Borax 300 "
Charcoal 50 "
Place two crucibles to warm during the time occupied in the preparation
of the mixture, then put it into the warm crucible; take 100 grains
more of litharge, and powder it over the contents in the vessel.
Prepare in this manner a second mixture for the other crucible, place
them both in the furnace, and put plenty of coke round them. The
mixtures may be melted in an ordinary wind or melting furnace, such
as is used by jewellers in the preparation of their material for
art working. The fusion should take place very gradually at first,
as silver in combination with lead is sensibly volatile at a high
temperature: it may then be continued at a low heat for twenty-five
minutes, and finally the operation may be completed with a full red
heat for five minutes longer.
During the process of fusing the contents of the crucible may be
watched by removing one of the bricks from the top of the furnace,
and when the whole mass has become quite liquid the crucible must
be seized with a pair of suitable tongs, tapped once or twice very
lightly against the side of the furnace to procure the settlement of
the contents, and immediately poured into an iron mould, previously
warmed and greased to prevent adhesion and spitting. Allow the mould
to remain for some time, in order to partially cool, and then plunge
it into a vessel of cold water. On cooling, the metallic elements
will be found incorporated into a button, the slag can then easily be
removed by tapping with a hammer on the edge, and the plunging into
cold water greatly facilitates this separation. The whole mass has then
to be cupelled, in order to separate the silver from the lead and other
metals.
[Illustration: Fig. 3. Fire-clay Fusing Cup.]
Silver ores, containing a large proportion of the sulphides (chemical
combinations of sulphur with metallic substances) of other metals,
may be easily assayed by the scorification process, which is, without
exception, applicable to the assay of all kinds of argentiferous ores;
and is one of the best, most simple, and most exact methods that can
possibly be employed in the extraction of silver from its ores. This
process, like that of fusion with litharge, already described, has the
effect of producing an alloy, and subsequently requires cupellation.
The ore is first well pounded, and then put into a small shallow vessel
made of close-grained refractory fire-clay (Fig. 3), with an excess
of finely granulated lead and some borax. The fusing cup or scorifier
employed in this process should be about 1-1/2 in. high and 2-1/2 ins.
in its greatest diameter; some assayers, however, use them deeper in
proportion to their width, and representing in form the end of an egg.
The object of this shape is to preserve the bath of molten metal at
the bottom, and that it may always be well covered and protected by
the slag on the top during the process of fusing. In the scorification
method the principles are exactly the reverse of those of the crucible
assay; for in the latter the object is to reduce the oxide of lead to
a metallic state, whereas in the former the metallic lead added to the
pounded ore in the scorifier is oxidized by being fused in contact with
the air. The charge for this assay may be as follows:--
Well pounded ore 60 grains.
Finely granulated lead 600 "
Borax anhydrous 100 "
Powdered anthracite 5 "
The cups or scorifiers should be charged in the following manner: well
mix the silver ore with 300 grains of granulated lead; place this
mixture in a scorifier, and add 300 grs. more of granulated lead, and
over the top of the whole put the burnt borax. The vessel may then be
placed in an ordinary assay furnace or muffle, as many being introduced
at one time as there is room for in the furnace, and submitted to the
strongest heat for about thirty minutes; during the greater portion
of this time the door should be kept closed, especially for the first
fifteen minutes. On opening the muffle-door a current of air passes
through the furnace, converting a portion of the lead into litharge;
this enters into combination with the earthy portions of the ore, the
other metallic sulphides, and also the borax, producing a fusible slag
on the surface of the metallic bath, extending over the whole surface
of the scorifier. The excess of lead is thus protected by this film or
flux from the oxidizing effects of the currents of air admitted into
the furnace, and remains united with whatever silver there may be in
the ore, in a metallic state.
The fusing should be continued longer than the thirty minutes--in
fact until the slag or flux is reduced into a perfectly liquid
state; stirring it well with a slender iron rod will facilitate the
operation, as it will tend to mix with the mass any hard portions
remaining undissolved and attached to the sides or other parts of
the vessels. This condition of the flux is absolutely indispensable;
when the slags are quite liquid, which with a strong fire will take
place in from thirty to forty minutes, wrap up in a piece of paper the
powdered anthracite, and drop it into the scorifier while still in the
furnace or muffle. The object of adding the anthracite at the last
moment is to reduce any minute portions of the metal that may exist
in the slags, and remain separated from the bulk. When the anthracite
has burnt off, which process usually takes about five minutes, this
point is considered to have been attained, and the operation is then
complete. The scorifier may be immediately withdrawn from the fire,
and the contents poured into a suitable casting-mould, of the form
represented in Fig. 4, a button of silver lead being the result. When
cold, the metallic mass is readily separated from the slag or flux by
slightly tapping with a hammer; the former may then be passed on to
the next operation, viz. to be purified of its lead by the process of
cupellation, which will be presently described.
When there is not enough borax present the assayer will observe an
infusible skin floating upon the surface; should this be the case more
borax must at once be employed, in order to dissolve such impurity.
When a chloride of silver ore is to be assayed, carbonate of soda must
be added to the mixture to prevent sublimation.
The following method of assaying is adopted in several large
Continental establishments, where the ores have, beside the usual
earthy matter and the sulphides of lead, an admixture of zinc, iron,
and copper. The process is precisely similar to the crucible assay,
in the case of genuine silver ores, as already described--with this
exception, that no more lead is added than the ores then contain--that
is, if we are treating _galena_ or _silver lead_; other ores require
different treatment according to their known composition. In this
process wrought-iron crucibles are employed having the form and shape
as shown in Fig. 5. They are made of thick iron plate, and are rendered
secure by welding the edges firmly together. Their dimensions are as
follows: a depth of 4-1/2 ins., with a thickness of iron at the bottom
of 1-1/2 in., and a 1/4 of an inch in the sides; the diameter at the
top of the crucible should be about 2-1/2 ins., and at the bottom
between 2 and 2-1/4 ins. A mechanical mixture or flux is prepared
to use with the ores to which we have referred, consisting of the
following chemicals, all of which should be finely powdered and well
mixed with the ore to be assayed:--
Carbonate of soda 6 parts.
Tartar 3 "
Saltpetre 2 "
Borax 1 part.
The furnace used for this assay is the ordinary one, having rather a
high chimney, to insure a perfect draught. In effecting the reduction
of the silver, the crucible is first placed as before on the fire, and
allowed to become hot; when this is accomplished, take
Well powdered ore 480 grains.
Prepared flux 500 "
These ingredients should be thoroughly mixed together, and put into the
red hot crucible. Fuse at a low heat for about twenty minutes, when
the whole will be in a perfect state of fusion; then give about five
minutes strong heat, and at the end of that time the crucible may be
withdrawn, and its contents poured into an iron mould, as represented
in Fig. 4, having one or two conical holes for the reception of the
fused mass. The silver and lead collect at the bottom of the mould by
reason of its high specific gravity. It may be removed by reversing
the position of the latter, when a gentle tap or two will deprive it
of that slag or flux which is usually attached to it. A large quantity
of silver can be readily collected from its ores by an alternate use
of crucibles, in which case it is possible to make a regular number of
fusions per hour. Wrought-iron crucibles, when strongly prepared and
carefully made, will stand about thirty of these fusions, giving way in
the end on account of the action of the sulphur contained in the ores.
[Illustration: Fig. 4. Iron Casting-moulds.]
Another kind of crucible, in addition to those already mentioned, is
used by the trade, and is recommended by many assayers as superior to
all others. Fig. 6 represents the form of it. It is about 4-1/2 ins.
high, and 2 ins. in its greatest interior diameter, being in the form
of a skittle. The charge consists of the following in this assay:
Finely powdered ore 60 grains.
Small pieces of iron 12 "
Black flux 180 "
Common salt 50 "
Put the powdered ore into the crucible, and place upon it the iron,
which should not be in the form of filings or dust, but in small
pieces; upon the ore and iron should be put the black flux, and
lastly the common salt must be placed above all these substances as
a protection against the air. The crucibles, as many as convenient,
may now be introduced into the furnace, and slowly raised to a strong
red heat, at which temperature they should be kept for about half an
hour; at the end of that period they should be removed from the fire,
slightly tapped to settle the contents, and then placed aside to cool.
When this has taken place, a few blows with a hammer near the base of
the crucibles, each in turn, will soon expose the button of silver
attached to the undecomposed iron; the latter substance may, however,
be easily detached by a few well-directed blows with the hammer.
[Illustration: Fig. 5. Iron Crucible for Assay.]
[Illustration: Fig. 6. Fire-clay Crucible for Assay.]
In order to ascertain the exact amount of the precious metal--that is,
the silver--contained in the buttons of lead obtained as the results of
the foregoing operations, they are subjected to a purifying process by
the metallurgist, called cupellation. By this means the lead and other
impurities are driven off by heat in contact with a current of air, and
the silver is left behind in a pure state. To perform this operation it
is necessary to expose the buttons on some absorbing medium or porous
support, and this support is commonly known as a _cupel_. No doubt
many porous substances could be made available for the formation of
cupels, but bone-ash is the best for all practical purposes, such as
are required by the assayer. The bone-ash, in the condition of a very
fine powder, is mixed with a little water in which has been dissolved
a small quantity of potash, and moulded into the desired shape. The
cupels are tightly consolidated by pressure in an iron mould of the
form shown in Fig. 7, which is the best in use, being well adapted for
the manufacture of cupels. It consists of a slightly conical steel
ring, 2 ins. in depth, and about 1-1/2 in. in diameter at the top
internally; a steel die with a wooden handle (Fig. 8) is made to fit
the mould. To make a cupel the space in the ring is nearly filled with
the moistened bone-ash, and pressed down by the hand, and afterwards
by the die, the latter being driven into the ring by the application
of a wooden mallet (Fig. 9) to the handle of the die. It will be seen
from the illustration that the die forms a cavity in the cupel capable
of receiving the charge of metal for assay. When the bone-ash has been
sufficiently compressed, the die is withdrawn, and the cupel removed
from the ring. This is a delicate operation, as sometimes the edges of
the cupel are liable to be injured; to prevent which and facilitate
the removal a loose plate of iron, exactly fitting the bottom of the
mould, should be introduced previous to putting in the bone-ash. The
iron plate of course being removed with the cupel, it must be replaced
before another can be made. By introducing a cylindrical piece of wood
to the lower aperture of the steel ring, the cupel can be removed
without difficulty.
[Illustration: Fig. 7. Cupel Mould.]
[Illustration: Fig. 8. Die for Cupel.]
[Illustration: Fig. 9. Wooden Mallet.]
The size of the cupel should always be regulated according to the
quantity of foreign matter to be absorbed, it being generally
understood that the material of which it is formed takes up double its
weight of lead. The process of cupelling is conducted in the furnace of
the assayer, an apparatus of peculiar construction, the most important
part of which, however, is the muffle (Fig. 10), consisting of a
small arched oven of fire-clay closed at one end, and furnished with
perpendicular slits in the sides, in order to allow of a free access of
air to the cupels inside.
[Illustration: Fig. 10. Assayer's Muffle for Cupels.]
[Illustration: Fig. 11. Cupel Tongs.]
[Illustration: Fig. 12. Cupels, section and perspective views.]
The position of the muffle in the furnace is so arranged that it can
be readily heated on every side; and when it has become red hot, six
or eight cupels, previously well dried, are taken and placed on the
floor of it, which should be covered with a thin layer of bone-ash.
The form of tongs required for this purpose is shown in Fig. 11. When
the cupels have been raised to the temperature of the muffle itself,
the assays are put in by a very slender pair of tongs, the door of
the furnace is then closed for a few minutes, when the metal will
have become fused, and the litharge will begin to be taken up by the
bone-ash of which the cupel is composed. The temperature of the furnace
is now lowered as much as possible, although not to such an extent that
it will retard the progress of oxidation and absorption. When nearly
the whole of the lead has been thus absorbed, the bead remaining will
have become very rich in silver, and, as the oxidation proceeds, will
appear much agitated, assuming a rapid circular movement, and revolving
with great rapidity. The silver gradually concentrates itself in the
centre of the cupel, taking the form of a globule, and at this stage
the fire should be made sharper, the operation being carefully watched.
When the last particle of lead leaves the silver, the agitation will
suddenly cease, and a beautiful phenomenon be witnessed, called by
assayers the _brightening_. The button of silver then becomes brilliant
and immovable, and the operation, when this takes place, is complete.
The cupel must be cooled with very great care, in order to prevent the
silver from _sprouting_; which if allowed to take place would result
in considerable loss, besides destroying the accuracy of the assay.
To prevent this sprouting it is a good plan immediately to cover the
cupel by another, which has been heated for that purpose; the two are
withdrawn together, and allowed to remain at the mouth of the muffle
until the silver has become solid; the metal is then in a state of
almost chemical purity, and may be detached and weighed. Previous to
the latter, however, it should be carefully cleansed from all foreign
matter, and flattened on a smooth-faced anvil, this process greatly
assisting in the removal of any oxide of lead, which not unfrequently
attaches itself to the globule of silver. The weighing is conducted
with a pair of scales having an extremely delicate balance; and where
any commercial transaction depends upon the accuracy of the assay, it
is always imperative to make several tests of the same sample, to avoid
the consequences of any accident or mistake.
The chief element in combination with silver on the large scale is
lead. Formerly the plan adopted in the separation of this metal
was cupellation alone. This process on the large scale is somewhat
different from that just described; and as it may appear to the reader
interesting and instructive, a brief explanation of it may not be
considered out of place.
CHAPTER IV.
The Cupellation of Silver Ores.
This interesting process is performed in a reverberatory furnace of
a very peculiar construction, the cupel employed on the large scale
differing somewhat from the ordinary one, being considerably larger and
varying also in form. It consists of a strong oval wrought-iron ring,
with a part of the full shape omitted, as shown in accompanying sketch,
in order to allow of the overflow of lead during the process, in the
form of litharge. This iron ring, known as the _test ring_, contains
the cupel, and in order to prepare the latter, the frame, which
measures about 60 ins. in its longest diameter, 40 ins. in breadth, and
6 ins. in depth, is strengthened by having a number of broad strips of
iron seamed across the bottom by riveting to the sides of it. The cupel
itself is prepared for use by taking finely ground bone-ash, together
with a little carbonate of potash, and working them up with just
sufficient water to make the mass cohere properly; the carbonate of
potash may be advantageously dissolved in the water; the latter is then
applied in small quantities at a time to the bone-ash until the proper
coherency has been obtained; of the total quantity of bone-ash employed
in the operation, 2 per cent. of potash will be _quantum sufficit_ to
mix with it. The iron frame, or test, is then filled with the mixture,
and it is pressed down into a solid compact mass, the centre part
being hollowed out with a small trowel, the sides sloping towards the
concavity in the middle; the hollow should not however be extended more
than within 1 to 1-1/2 in. of the bottom of the frame, and above the
iron bars. The cupel forms the hearth of the furnace we have spoken
of, and of which Fig. 13 is a sectional view; it is removable, and not
a fixture in the furnace. It must be left for several days to dry,
after having been constructed as described, when it is ready for use,
and only requires firmly wedging in its place beneath the arch of the
furnace.
[Illustration: Fig. 13. Cupels, section and perspective views.]
The fire should be only very moderate at the commencement of the
operation, and the furnace slowly raised in temperature, lest the cupel
should crack by being too quickly heated. As the temperature increases,
if without any apparent defects in the bone-ash cupel, or hearth, which
it may now be termed, the wind or blast, generally driven by a fan, is
thrown in through a nozzle, or an aperture in the furnace, which, for
facilitating the immediate removal of the bone-ash hearth, is placed
upon an iron car, and runs beneath the vault of the furnace on rails,
so that it may thus be very readily withdrawn when found necessary. The
admission of a current of air into the furnace oxidizes the excess of
lead, in combination with the silver, producing litharge on the surface
of the molten mass; the formation of the litharge takes place rapidly,
and it is continually blown forward by the strength of the blast as
fast as it is produced, running through a gap or channel specially made
for the purpose in the mouth of the cupel into a movable iron pot which
is placed for its reception. The continual oxidization and flow-off of
the lead alters the respective proportions of the metals in the cupel.
For this reason it is always kept full of lead ore, which is effected
by taking it in its fused state from a kettle in which it is ready
melted by means of a long-handled ladle; and thus about 500 or 600 lbs.
of metal are constantly kept in this bone-ash cupel or hearth.
As the silver necessarily increases in the hearth, it will require to
be occasionally withdrawn, in order to make room for a further supply
of lead ore. This process is adopted when it reaches about from 8 to 10
per cent. of silver to the ton (between 2,000 and 3,000 ozs.), and may
be effectually performed by drilling a hole underneath the cupel, and
letting the silver flow through it into a receptacle placed to receive
it. Of course the operations of the furnace are arrested while these
manipulations are being carried on. After the withdrawal of the silver,
the hole is closed up again with a plug of moistened bone-ash prepared
as before; when the process may be continued a second time by giving
500 or 600 lbs. of fresh lead ore to the cupel. Thus a single cupel
will often last 48 hours, and 6 or 7 tons of lead may be oxidized upon
it.
We have already observed that the prolongation of the cupelling
process increases the richness of the remaining alloy, and this very
rich silver-lead alloy is again subjected to a second operation in
cupelling. This process of assaying or refining is similar in every
respect to the former, and is often performed in the same furnace, the
cupel being first of all brought to almost a bright red heat, when
about 600 lbs. of the silver-lead alloy are added, and a strong current
of air given in order to oxidize the remaining lead in combination with
the silver. In this operation the material under treatment, previous
to its introduction to the cupel, should be melted in a kettle easy of
access, and added in its fused state. The current of air in connection
with the heat of the furnace immediately begins to purify the silver by
oxidizing the lead, and forms litharge, which passes off through the
channel provided in the mouth of the cupel; as this proceeds, fresh
silver-lead alloy is added, to keep the level of the metal always at
the same height. This is continued until some three tons of the alloy
from the first cupellation have been put in, and when about 600 or 700
lbs. of silver are collected in the cupel.
When the cupel has received the above proportion of metal, the addition
of the alloy ceases, and the silver is allowed to purify. The litharge
which passes off towards the close of this process will be richer
in silver than in the former one; consequently it is found best in
practical metallurgical operations to treat in a special manner the
last part of silver cupelling on the large scale, for it needs very
careful management indeed to secure all the silver, especially to do so
in a fine state. Towards the completion of the process the fire should
be increased considerably, in order to keep the silver thoroughly
melted, and also to oxidize and completely remove every trace of lead
that is possible. As it begins to purify itself from the remaining lead
a characteristic brightness will be perceived. When this takes place
the fire must be lowered, the wind or blast stopped, and the metal left
to cool gradually. This latter proceeding is of some importance, as a
too sudden cooling of the surface causes the interior of the metal to
expand and shoot, by which means little globules of silver may be lost;
therefore it should be allowed to cool very slowly.
The iron ring encircling the cupel with its contents may now be drawn
from beneath the arch of the furnace, and the cake of silver taken from
its bed in the bone-ash which formed the vessel, and cleaned of any
impurity; when it may be re-melted in a plumbago crucible, and cast
into ingot moulds. These moulds should be made of iron, and should
always, when used for this purpose, be warmed and greased a little,
previous to the introduction of the melted material, to prevent the
metal from spitting and adhering to it. If skilfully treated during
the process of cupellation, the desilvered lead seldom contains more
than ·002 to ·003 per cent. of silver to the test assay of 200 grs., or
between six and ten pennyweights to the ton, beyond which point it is
unprofitable to carry on the operation.
The litharge which is formed and passes off during the process
gradually grows richer in silver towards the end of the cupellation. It
probably contains after concentration about thirty to forty ounces of
silver to the ton of litharge. This is again subjected to the several
operations of the same kind for the recovery of the silver.
It is somewhat remarkable that the present method of recovering and
purifying this metal bears a strong resemblance to that employed in
ancient times, and which is spoken of in the Holy Scriptures by the
prophet Ezekiel (xxii. 18 and 20): "Son of man, the house of Israel is
to me become dross: all they are brass, and tin, and iron, and lead,
in the midst of the furnace; they are even the dross of silver." And
also, "As they gather silver, and brass, and iron, and lead, and tin,
into the midst of the furnace, to blow the fire upon it, to melt it; so
will I gather you in mine anger and in my fury, and I will leave you
there, and melt you." The celebrated metallurgist Dr. Lamborn says,
"Only those who have seen, beneath the glowing arch at the smelting
works, flames surging wave after wave across the surface of the liquid
metal, carrying all the substances, here called dross, from the pure
silver; and only those who have heard the roar of the fiery blast,
that ceases neither day nor night, until its task of purification is
accomplished,--can appreciate the terrible force of the figure made use
of by the prophet." According to the above scriptural passage it is
evident that the ancients were in possession of the first rudiments of
assaying, and understood to some extent the purification of metals; but
scriptural testimony does not point out with what amount of skill and
success these operations were performed. Judging from the appliances
which have been handed down from generation to generation, we are
inclined to think they must have been practised somewhat rudely; for
it has been left to the present school of scientific and practical
metallurgists to found and develop the art in the direction of that
commercial success to which it has at the present day attained.
This plan of cupellation which we have just described is still adopted
in many continental works in the assaying of silver-lead ores. In
England the system has been almost entirely superseded by one invented
by the late Mr. Pattinson of Newcastle, and which is confidently stated
to be far more convenient in practice.
CHAPTER V.
The Alloys of Silver.
Fine silver enters freely into combination with nearly all the useful
metals, but its most important alloys are those prepared from copper,
the latter substance being more suitable for the production of
silversmith's work than any other; whilst it produces a more pleasing
effect, if not over-alloyed, in regard to finish. Silver articles,
especially of the _filigree_ kinds, if the designs are good, possess
a very tasteful appearance. In treating of the alloys of silver, it
is our intention, first, to give a cursory glance at the chemical
and physical properties of the metals which form these alloys. Such
a description, although brief, will, we believe, prove of essential
service, not only to working silversmiths and metalsmiths, but also to
goldsmiths and jewellers, who are constantly manipulating with these
inferior metals in precisely the same way as the silversmith. Besides,
such information cannot, we apprehend, fail to be useful, whether to
the student, the theorist, or the practical worker.
An alloy is the union of two or more metals by fusion, so as to form
a metallic compound. It may consist of any number of the metallic
elements, and in any proportion, provided they will chemically combine,
always excepting mercury as one of the ingredients. In this latter case
the mixture is called an _amalgam_. Chemistry has made us acquainted
with about forty-nine metals; of that number, however, not more than
fourteen are employed to any considerable extent for industrial art
purposes. They are as follow: Gold, silver, copper, zinc, platinum,
aluminum, nickel, iron, mercury, lead, tin, arsenic, antimony, and
bismuth. Some of these are occasionally employed for _special_
purposes in the arts in their pure state; but where hardness is to be
a distinguishing characteristic, combined with certain variations in
shades of colour, a union is effected of two or more of these metals
in different proportions, by fusion and stirring, so as to form the
requisite alloy. Metals used in the pure state, that is, without any
mixture of alloy, have very few applications in regard to industrial
pursuits and the arts. The precious metals--gold, silver, &c.--would
be much too soft, while, on the other hand, arsenic, bismuth,
and antimony would be far too brittle to be employed alone for
manufacturing purposes. It is quite possible to effect some thousands
of alloys, but there do not appear to have been more than about three
hundred practised successfully for commercial purposes.
The principal alloy of silver, as we have already remarked, is copper;
but, occasionally, nickel, and even zinc are employed in the case of
the commoner qualities of silver. Tin is also used in the preparation
of solder for these qualities, in order to render it the more easy of
fusion when used for soldering the work. Of the distinctive features of
these elements of silver-alloy we shall now speak with some amount of
detail.
Silver will unite with copper in various proportions by melting the
two ingredients together, and stirring them whilst in a fused state. A
product will thus be formed differing physically in character from fine
silver, caused by the loss of some little of the latter's ductility
and malleability; but, on the other hand, a compound will be produced
harder and more elastic, which is in every sense better adapted to the
manufacture and also to the durability of the articles made by the
silversmith.
_Copper_, like the precious metals, appears to have been known from
a very early age, being one of the six metals spoken of in the Old
Testament; and described by the historian as being also one of the
seven made use of by the ancient philosopher. It is of a reddish
colour, malleable, ductile, and tenacious. It is largely employed in
alloying both gold and silver for the manufacture of jewellery and
other articles. With regard to malleability, it stands next to gold and
silver in the list of useful metals; in ductility it occupies the fifth
position; and in tenacity one only is superior, viz. iron. It is not
very fixed in the fire, for if subjected to a long-continued heat it
loses a part of its substance; for this reason the alloys of silver and
copper should be carefully watched in the crucible to prevent this loss
when under the action of the fire.
When struck copper gives only a feeble sound, and is easily abraded by
the file. It fuses at a good white heat, or about 1994° Fahr., although
some authors have given it as 1996° Fahr. Its specific gravity varies
between 8·88 for cast copper, and 8·96 when rolled and hammered. It
loses between one-eighth and one-ninth, or 4/35ths, of its weight in
water. When exposed to a damp atmosphere a greenish oxide, called
verdigris, is produced on its surface, and this is one of the reasons
why silver articles containing a percentage of copper become so
readily discoloured if left exposed to atmospheric influences; copper
also, if heated in contact with the air, quickly becomes oxidized,
and, on being touched, scales fall off: these form the _protoxide
of copper_. If this process is frequently repeated under a great
heat, each time the metal is operated upon it loses a part of its
malleability and ductility, which are both eminent characteristics of
the pure metal. Most of the ordinary acids act on copper but slowly in
the cold, but nitric acid very readily dissolves it, even if largely
diluted. Copper amalgamates with most of the metals, and its subsidiary
alloys are very largely employed in the arts and manufactures of every
kind.
The bean-shot copper of commerce, costing about a shilling per pound
avoirdupois weight, is quite good enough for all the practical purposes
of the silversmith.
[Illustration: Fig. 14. _Venus._ Egyptian Mark for Copper.]
The name given to this metal by the alchemists was _Venus_ (Fig. 14),
which is one of the principal planets, whose orbit is situated between
the Earth and Mercury. The scientific name of _cuprum_ for copper
is derived from the Isle of Cyprus, where, it is said by Pliny, the
Greeks discovered the method of mining and working it. Copper is found
distributed all over the world; a considerable portion, however, is
found in the United Kingdom.
_Nickel._--This metal is found chiefly in the Hartz Mountains. It
was formerly called by the Germans "Kupfer nickel," or false copper,
"nickel" being a term of detraction. It was first discovered about a
century and a half ago by Cronstedt. It has a greyish-white colour, and
is slightly magnetic, _i.e._ it is attracted by the magnet in the same
way as iron and steel, but it loses this property if heated to about
600° Fahr. Its specific gravity varies between 8·40 and 8·50, according
to the amount of compression it has received, and it is rather brittle;
it may, however, be drawn into wire, and rolled flat, or into sheets.
It is considerably harder and less ductile than any of the other metals
employed in jeweller's and silversmith's work. In hardness it nearly
approaches iron, and on this account, when polished, a characteristic
brightness is produced. The malleability of nickel is less than that of
iron, standing tenth in the list of useful metals; and in ductility it
also occupies the tenth position. Nickel is very infusible, and does
not so easily oxidize or tarnish at ordinary temperatures as copper
does. Several countries have tried to employ it in the manufacture of
small coin for the currency, but its use has now been almost abandoned.
Nickel alloys are much used in the arts for manufacturing purposes,
under the name of "German silver," there being large demand for
this metal, as it forms the hard white alloy much used in making
"electro-plate," and on which silver is afterwards deposited. It also
is used in common silver alloys, in order to keep up the whiteness of
the latter element, the addition of too large a proportion of copper
maintaining the tint of the latter metal, in too strong a degree to
be altogether employed by the silver-worker. Nickel is sometimes
_specially_ employed, in combination with other metals, to replace
or imitate silver in the manufacture of commercial wares, while with
copper, zinc, tin, &c., it forms very useful alloys, producing great
hardness.
_Zinc._--This metal in its pure state is sometimes called _spelter_. At
the present day it is not much used for alloying silver; but, as it is
commonly employed in the preparation of silver-solder, it is necessary
that the amateur and the student should know, as well as the practical
mechanic, the distinctive characteristics of it, together with the
qualities it imparts to others when in combination with them. As a
metallic substance it was unknown until a long time subsequent to the
discovery of the principal metals; and only since the commencement of
the present century has its uses been thoroughly known and appreciated
in the industrial world. In its pure state, zinc is a bluish-white
metal, hard and highly crystalline; but, when raised to a heat of
between 250° and 300° Fahr., it is malleable, and may safely be rolled
and hammered: it is in this way that the zinc of commerce is produced.
Zinc may be annealed by placing it for a time in boiling water.
Its specific gravity varies between 6·8 and 7·2, according to the
previous kind of mechanical treatment it has received. At 773° Fahr.
it melts, and is quickly oxidized by exposure to a current of air,
emitting white vapours, which rise into the air, and are not unlike
cotton-flakes; oxide of zinc is thus formed by the burning away of
the zinc. Spelter or zinc is employed by jewellers in the manufacture
of bright gold alloys, as it gives liveliness of colour to their
wares not to be equalled by any other metal. (For the proportions
and treatment of this composition see "The Goldsmith's Handbook.")
It may be alloyed with most of the metals we have named; its uses in
roofing, gutters, spouting, and chimney-pots being all well known.
All the acids very readily attack it in the gold, and even when
largely diluted; it speedily tarnishes, and becomes covered with a
white oxide which protects the metal from atmospheric influences. In
point of malleability zinc stands eighth among the metals, seventh in
ductility, and as regards tenacity about seventh also. In chemistry it
is represented by the symbol _Zn_. Its value when in a state of purity,
commercially speaking, is about 4_d._ per. lb.
_Tin._--This appears to have been one of the oldest known metals, and
was employed in the Egyptian arts by the ancients, in combination
with copper. Its colour is white, with a shining lustre almost as
brilliant as that of silver, but it tarnishes much more quickly than
alloys of the latter metal. With the exception of aluminum and zinc,
it is the lightest of all the metals, its density being between 7·0
and 7·3, whether cast, hammered, or rolled. It is found in abundance
in Cornwall, where it was also obtained at a very early period by the
Ph[oe]nicians; and it is reported in Soame's "Latin Church," p. 30,
that it was through the medium of the trade in tin that Christianity
was first introduced into this country. Tin is not of a fixed nature
like gold or silver, but melts in a moderate fire long before it
becomes red hot, or about 442° Fahr. It is rapidly oxidized when kept
for a long time in a fire having a free access to the air; and it is
dissolved by hydrochloric, sulphuric, and nitric acids, the latter
acting on it most powerfully. Tin should not be alloyed with gold or
silver, as with either of these it easily enters into combination by
fusion, rendering them extremely brittle, especially in the case of
silver, which becomes by the least mixture of it so brittle that it is
totally unfit for the work of the silversmith. However, for solder,
for filing into dust, it may be advantageously employed to promote a
quicker fusion; but even for this it should be avoided where it is
possible to do so. The vapours of tin are also permanently injurious
in the melting of gold, silver, and their alloys, as they render them
very unworkable, and the operator being often at a loss to understand
the cause of his misfortune; therefore, in melting silver alloys, it is
advisable to avoid as much as possible the introduction of little bits
of scrap tin into the furnace. If such a thing should happen, however,
make the fire once or twice stronger in order that the tin may all be
destroyed before the crucible containing the silver alloy is put in.
[Illustration: Fig. 15. _Jupiter._ Egyptian mark for Tin.]
Tin is very malleable, moderately ductile, and tenacious, being fifth
on the list for malleability, eighth for ductility, and eighth for
tenacity. The Egyptian mark or symbol for tin (sign of "Jupiter") was
the same as is represented in Fig. 15, and related to the planet of
that name, one remarkable for its brightness. _In mythology_ it is
understood as representing the supreme deity of the Greeks and Romans.
The modern scientific name for tin is Sn. Tin loses over one-seventh,
or 4/29ths, of its weight in water from its absolute weight in air. In
the next chapter we shall treat of the mixing of silver alloys, &c.,
and in order to make our information regarding the various metals so
employed as complete as possible, we shall conclude this one with the
following tables, each of which will no doubt be found useful:--
Table of Metallic Elements.
+-----------------------+----------+---------------------+
| Names of Elements. | Symbols. | Specific Gravities. |
+-----------------------+----------+---------------------|
| Platinum | Pt | 21·40 to 21·50 |
| Gold | Au | 19·25 " 19·50 |
| Mercury | Hg | 13·56 " 13·59 |
| Lead | Pb | 11·40 " 11·45 |
| Silver | Ag | 10·47 " 10·50 |
| Bismuth | Bi | 9·82 " 9·90 |
| Copper | Cu | 8·89 " 8·96 |
| Nickel | Ni | 8·50 " 8·60 |
| Iron | Fe | 7·77 " 7·80 |
| Tin | Sn | 7·25 " 7·30 |
| Zinc | Zn | 6·80 " 7·20 |
| Antimony | Sb | 6·75 " 6·80 |
| Arsenic | As | 5·70 " 5·90 |
| Aluminum | Al | 2·56 " 2·60 |
+-----------------------+----------+---------------------+
Melting-points of the Principal Metals.
+--------------------+--------------+-----------------+
| Names of Elements. | Fahrenheit. | Centigrade. |
+--------------------+--------------+-----------------+
| Platinum | { Infusible, except by the |
| | { oxyhydrogen blow-pipe. |
| Cast Iron | 2786° | 1530° |
| Nickel | 2700° | 1482° |
| Gold | 2016° | 1102° |
| Copper | 1994° | 1090° |
| Silver | 1873° | 1023° |
| Aluminum | 1300° | 705° |
| Zinc | 773° | 412° |
| Lead | 612° | 322° |
| Bismuth | 497° | 258° |
| Tin | 442° | 228° |
| Antimony | Fuses a little below red heat. |
| Arsenic | Volatilises before it fuses. |
+--------------------+--------------------------------+
Physical Properties of the Principal Metals.
+---------------+------------+-----------------+
| Malleability. | Ductility. | Tenacity. |
+---------------+------------+-----------------+
| Gold | Gold | Iron 549 |
| Silver | Silver | Copper 302 |
| Copper | Platinum | Aluminum 300 |
| Aluminum | Iron | Platinum 274 |
| Tin | Copper | Silver 187 |
| Platinum | Aluminum | Gold 150½ |
| Lead | Zinc | Zinc 109½ |
| Zinc | Tin | Tin 34½ |
| Iron | Lead | Lead 27½ |
| Nickel | Nickel | [B] |
+---------------+------------+-----------------+
[B] The above weights were lbs. sustained by 0·787 of a line in
diameter, in wires of the various metals.
CHAPTER VI.[C]
Various Qualities of Silver.
[C] See observations on Depreciation of Cost Price of Silver in Preface
to Fourth Edition (pp. vii, viii), and the new Table of Cost Prices of
Alloys in this Chapter, following the Preface (p. ix).
The chemical and physical properties of fine silver having been dealt
with in a preceding chapter, we shall not refer to them again in
detail; but, as we have already observed that it is sometimes employed
in _its pure_ state for special purposes, it is desirable that we
should point out the uses to which it has been applied, especially
those of a mechanical nature. With reference to the latter part of the
subject we will now proceed to describe the commercial utility of the
metal.
One of the greatest demands for pure silver--if not the greatest of
all--is in the manufacture of fine filigree work, a branch of industry
extensively practised on the Continent. This kind of silversmith's
work was attempted to be revived in this country during the years
1864-5, Birmingham and London being the principal places where the
manufacture was carried on; but the success of the undertaking as a
staple industry must, at the most, have been only a partial one, for
it soon declined, and the trade was thus virtually left, as before, in
the hands of our Eastern competitors; most of whom produce splendid
specimens of the art of filigree and fine wire-working. In India this
work is wonderfully performed, and it is truly marvellous to witness
the beautiful handiwork of the natives who practise this craft. Their
productions are quite the work of the true artist, almost every article
representing Nature in some of her various forms, such as flowers,
animals, serpents, &c., and these are so skilfully imitated that no one
could possibly dispute either the faithfulness of the representation or
the ability of the workman. This is all the more surprising, because in
India the natives have not the modern mechanical appliances which we
possess in this country. The jeweller there represents to some extent
our travelling tinker, only with this difference, that the travelling
tinker in this country is generally an inexperienced and unskilful
workman, whereas the Indian, if we are to judge him by his work, must
be just the reverse.
Filigree wire-work is manufactured in Italy, Germany, Norway, and
Sweden, and the secret of these countries maintaining the monopoly
in this branch of the silversmith's trade is that labour there is
cheap; and not in any sense because English workmen cannot make the
articles in question. It is owing to this cheapness of labour and the
inexpensiveness of living that our Continental competitors can beat
us by underselling us in the market; and to no other cause can the
production of the foreign cheap article be assigned.
In India the art of working in silver and gold has long been practised,
and so particular are the workmen there about the absolute purity of
the metals they use, that they refine them by melting five times, under
a very strong blast heat, before commencing the work of manufacture.
The principal places where these art-manufactures are carried on are in
Southern India and at Trichinopoly; and in these districts the delicacy
and intricacy of the workmanship are brought to the greatest possible
perfection. The articles produced there are all "hand-made," and
wrought entirely with a few simple tools, such as a hammer and an anvil
(both of which are highly polished and burnished), a few fine pliers,
blow-pipes, burnishers, scrapers, a pair of fine dividers, and some
delicate scales and weights; these, with a few perforated steel-plates
for drawing the wire through, comprise the chief appliances of the
travelling native jewellers. The process of the work is very simple.
It is commenced by hammering out the metal upon the anvil, and when it
has assumed a certain degree of thinness the dividers are next brought
into requisition to mark it into certain widths, which are subsequently
cut into strips and drawn into very fine wire through perforated
steel-plates, a pair of strong pliers being used for the purpose. The
holes in the steel-plates consist of graduated sizes, and by this means
the strips of metal are soon considerably reduced; and when the proper
thinness has been attained the wire is ready for the exercise of the
practical skill and dexterity of the artisan, who produces from it the
best filigree work in the world. Most of the native jewellers have
books containing a variety of designs, but they more commonly work from
memory, without any reference to patterns.
The principal localities where this description of work is produced in
the highest perfection are Delhi, Cuttack, and Trichinopoly, in India;
and Genoa, Paris, Florence, Malta, Norway, and Sweden. The Indian
filigree work is the finest and cheapest in the world. The Maltese
manufacture a very good kind, and their crosses are much admired; so
also do the Chinese and Japanese, but the manufactures of these latter
countries are not so tasteful as those of India, consequently they have
not been so highly appreciated. Norway and Sweden produce filigree work
of a very light weight; but still their productions in this art will
not compare in regard to effect with the finest specimens from India.
We have said that the silver employed by the filigree worker should
be in every case absolutely pure; because, when it is quite fine, it
is extremely soft and pliable, so that it will remain in almost any
form the artist may choose to work it, without that springiness which
is found in all alloyed metals. However small might be the amount of
alloy contained in the metal, the least admixture of it would produce
an elasticity in the wire when pressed into form which would make it
unworkable for fine filigree purposes; and in this state it would be
the utter bane of the workman, as his progress would be altogether
impeded in the production of his work. It is of the greatest importance
that the spirals, and all the various forms required in filigree
working, should remain steadily in their places when pressed into
shape, without that rebounding which happens in the case of metals of
an elastic nature, and in consequence of which no really first-class
work can be performed in connection with this art. For such reasons
as these it will be at once palpable even to the ordinary reader that
fine silver should always be used in preference to alloyed in the
manufacture of filigree work.
The various ornaments of the filigree kind are commonly enclosed in
a rim of plain and somewhat stronger wire, which gives additional
strength to each part; and, when put together, tends to compose an
article of considerably greater durability. In England these outside
rims consist exclusively of sterling or standard silver, whilst all the
inner work is of the finer material.
There are several methods of preparing the wire called "filigree." The
oldest and the one almost invariably practised in India consists in the
first place in drawing down the wire in a circular form until the very
lowest possible thinness has been attained, and frequently annealing
it during the process, which is done by heating it to a red heat in a
muffle placed upon an iron or copper pan. When this process has been
effectually performed the wire is taken (if of the proper degree of
thinness) and doubled together; these two fine wires are then twisted
into one cord, which should be of the fineness desired. The wire
requires annealing more than once during the process of twisting, and
when it is completed it has a corded appearance, it is then ready for
the manufacture of the various articles comprised in this kind of work.
The old plan of twisting was accomplished in the following manner. One
end of the doubled wire being firmly secured in a vice or some other
suitable instrument, so as to prevent it from turning round and so
prevent the progress of the work, the other end of it was also firmly
secured in a small hand machine or vice, which was made to revolve by
turning a small handle with the right hand, the machine being held and
regulated with the left, in order to keep the wire out at its full
length so as to avoid knotting in the various parts of it; it was in
this manner that fine filigree wire was in the first instance made.
The second plan was somewhat different, and in regard to the last part
of the process it was certainly a great advantage, especially in the
saving of labour, as a greater quantity could be prepared in a much
less time than by the old method, that being slow in its progress. Here
the lathe was made to supply the place of the small hand machine, the
speed of which soon brought about the object in view.
The flattening of this twisted wire has now commonly come into use, and
is effected by passing it through small steel rollers, hardened and
polished. The object of this is soon manifest, as the labour-saving
process is brought prominently into play: the wire in the first place
need not be so finely drawn, and secondly the same filigree surface can
be made to appear upon the articles as before, by securing the edges
of the wires which show the filigree uppermost; and this is always the
case in manipulating with this kind of wire. This method is generally
in vogue with most filigree workers.
A third plan of preparing the material for the manufacture of filigree
work is, we believe, due to the ingenuity of a celebrated Birmingham
firm, who extensively practised this kind of work some years ago.
The secret is not now generally known to the trade, therefore a few
observations bearing upon it will not be unacceptable to those for
whose benefit we are writing. The process is commenced in the same
manner as before, in the preparation of the round wire, though this
need not be drawn so fine, because by this method we have no twisting.
When the round wire has arrived at the proper size it is flattened
in the manner already explained; and when this is done it should
be annealed, but experience will dictate best when this particular
process should be carried out. After this latter operation the wire is
submitted to the action of very small rollers, and bearing the pattern
required in small grooves of various sizes. The pattern takes effect
upon the edges of the wires only, and resembles the milled or serrated
edges of our coinage, only of course the latter bears no comparison
with regard to fineness. Lastly, the wire is again passed through the
flattening rollers, and then it is ready to be worked up into the
object desired.
Having gone through the general details of filigree working we shall
next direct our attention to the component parts and commercial uses of
the English standards, together with those of some other countries. In
England there are two silver standards, called respectively the old and
the new standards. They are as follows:--
Fine silver per lb. troy.
Old Standard, 11 oz. 2 dwts. = 925 millims.
New Standard, 11 oz. 10 dwts. = 959 millims.
The older of these appears to have been always the legally recognised
standard for the coinage, and also for the manufacture of plate. By
a law passed, however, in the reign of William III. (1697) it was
raised to 11 oz. 10 dwts. of fine silver in the pound troy weight. The
manufacture of silver articles from this standard was soon found to
be not so durable as those made under the older one; consequently the
silversmiths were permitted by a law passed in the reign of George III.
(1819) to manufacture from the former standard of 11 oz. 2 dwts., the
use of the new one being likewise permitted for the benefit of those
who chose to avail themselves of it; and to this day it remains an
English standard, though hardly ever employed.
By the Silver Coinage Act (10 Geo. 5), the fineness of the British
coinage was reduced on account of the increased price of silver
bullion; and the silver coinage now consists of one-half silver,
one-half alloy, one troy pound of silver being coined into sixty-six
shillings. The copper which composes the alloy in the silver coinage
hardens the material employed, and it is found to wear better.
In order to make the matter as simple as possible, we purpose giving a
few practical alloys, as follows:--
Old standard silver alloy, cost 4_s._ 4_d._ per oz.
oz. dwts. grs.
Fine Silver 0 18 12
Shot Copper 0 1 12
----------------
1 0 0
================
If it is intended that the above alloy should be for Hall-marking,
it will be advisable to add a little extra silver to the prepared
composition, because fine silver purchased from the refiner or bullion
dealer is never absolutely pure, consequently the work will not pass
the Hall; or better still alloy as follows:--
Old standard silver for Hall marking.
oz. dwts. grs.
Fine Silver 0 18 14
Shot Copper 0 1 10
----------------
1 0 0
================
The new standard silver is composed of 38-1/3-40ths of fine silver and
1-2/3-40ths of copper alloy; or millesimal fineness 959 parts of fine
silver and 41 parts of copper per 1,000 parts; the remedy being as
before 0·004 parts.
New standard silver alloy, cost 4_s._ 6_d._ per oz.
oz. dwts. grs.
Fine Silver 0 19 4
Shot Copper 0 0 20
----------------
1 0 0
================
New standard silver for Hall marking.
oz. dwts. grs.
Fine Silver 0 19 6
Shot Copper 0 0 18
----------------
1 0 0
================
Quality commonly used in England.
oz. dwts. grs.
Fine Silver 0 18 0
Shot Copper 0 2 0
----------------
1 0 0
================
The qualities of the silver employed by the English silversmiths are
invariably below the standard, the duties, assay charges, and loss of
time in sending the work to the Hall to be marked acting as a great
drawback to the trade in the midst of the keen competition of the
present day. Silver chains, brooches, buckles, collarets, &c. are
for the most part manufactured from inferior metal. In fact, some
manufacturers positively refuse to make Hall-marked goods, on account
of the great drawbacks attending the marking.
The alloys of silver are not calculated on the carat system, like
gold, but by certain numbers, or other distinctive features, well
understood by the particular firms which trade in silver wares. For
our present purpose it will be sufficient to distinguish them by using
the numerals, 1, 2, 3, 4, &c.; the alloy nearest approaching sterling
or standard we shall call No. 1, and so on downwards until the lowest
quality has been reached. We may state that silver does not lose its
whiteness if not alloyed below equal quantities of the two metals;
however, the alloys used in manufactures seldom reach so low a limit.
Silver alloy No. 1, cost 4_s._ 2_d._ per oz.
oz. dwts. grs.
Fine Silver 0 18 0
Shot Copper 0 2 0
----------------
1 0 0
================
Silver alloy No. 1, same as above.
oz. dwts. grs.
Fine Silver 1 0 0
Shot Copper 0 2 6
---------------
1 2 6
===============
Silver alloy No. 2, cost 3_s._ 9_d._ per oz.
oz. dwts. grs.
Fine Silver 0 16 0
Shot Copper 0 4 0
----------------
1 0 0
================
Silver alloy No. 2, same as above.
oz. dwts. grs.
Fine Silver 1 0 0
Shot Copper 0 5 0
----------------
1 5 0
================
Silver alloy No. 3, cost 3_s._ 6_d._ per oz.
oz. dwts. grs.
Fine silver 0 15 0
Shot copper 0 5 0
---------------
1 0 0
===============
Silver alloy No. 3, same as above.
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 0 6 16
---------------
1 6 16
===============
Silver alloy No. 4, cost 3_s._ 3_d._ per oz.
oz. dwts. grs.
Fine silver 0 14 0
Shot copper 0 6 0
---------------
1 0 0
===============
Silver alloy No. 4, same as above.
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 0 8 12
----------------
1 8 12
================
Silver alloy No. 5, cost 3_s._ 2_d._ per oz.
oz. dwts. grs.
Fine silver 0 13 12
Shot copper 0 6 12
----------------
1 0 0
================
Silver alloy No. 5, same as above.
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 0 9 18
----------------
1 9 18
================
Silver alloy No. 6, cost 3_s._ 1_d._ per oz.
oz. dwts. grs.
Fine silver 0 13 0
Shot copper 0 7 0
----------------
1 0 0
================
Silver alloy No. 6, same as above.
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 0 11 0
----------------
1 11 0
================
Silver alloy No. 7, cost 3_s._ per oz.
oz. dwts. grs.
Fine silver 0 12 12
Shot copper 0 7 12
----------------
1 0 0
================
Silver alloy No. 7, same as above.
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 0 12 0
----------------
1 12 0
================
Silver alloy No. 8, cost 2_s._ 10_d._ per oz.
oz. dwts. grs.
Fine silver 0 12 0
Shot copper 0 8 0
----------------
1 0 0
================
Silver alloy No. 8, same as before.
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 0 13 12
----------------
1 13 12
================
The qualities of the silver alloys have been reduced in this list to
various values, and the latter ones are as common as it is possible
to make them, without a great and perceptible change of colour taking
place in the prepared material. But if it be desired to work a still
more inferior metal, then another ingredient must enter into its
composition, in order to keep up the whiteness of the silver; and
this other metal employed is nickel, the alloys with which we shall
have occasion to refer to hereafter. Suffice it to say, however, that
these inferior alloys of silver, prepared with nickel, are not now
much employed by silversmiths in their art-manufactures. It will be
observed that we have recommended the employment of _shot_ copper in
the manufacture of silver alloys: we do so for two reasons--first,
because it can be purchased at a considerably cheaper rate than can the
ordinary forms of copper, costing only one shilling per lb., whilst the
ordinary prepared copper for alloying will cost double that amount;
and, secondly, if proper attention has been given to the melting and
casting process, the workable qualities of the metal will be found
everything that could be desired. Therefore an excellent material in
all respects can be produced by the means suggested at half the cost
of alloy. A considerable saving to a large firm might thus be easily
effected by its employment.
In France there are three silver standards--two to be employed by
silversmiths, and one for the coinage, as follows:--
Fine silver per lb. troy.
Silver ware, 11 oz. 8 dwts. = 950 millims.
Coinage, 10 oz. 16 dwts. = 900 millims.
Silver ware, 9 oz. 12 dwts. = 800 millims.
It will be seen from the above table that pre-war coinage in France did
not represent the highest standard, and also that their principal one
was inferior to our highest standard. French coinage contained 36-40ths
of fine silver and 4-40ths of copper alloy, or millesimal fineness 900
parts of fine silver and 100 parts of copper per 1,000 parts of metal;
the highest standard for silver wares contains 38-40ths of fine silver
and 2-40ths of copper alloy, or millesimal fineness 950 parts of fine
silver and 50 parts of copper per 1,000 parts of metal; the lowest
French standard for silver wares contains 32-40ths of fine silver and
8-40ths of copper alloy, or millesimal fineness 800 parts of fine
silver and 200 parts of copper per 1,000 parts of metal. The remedy is
millesimal fineness 0·005.
French alloy for coinage, 4_s._ 2_d._ per oz.
oz. dwts. grs.
Fine silver 0 18 0
Copper 0 2 0
-----------
1 0 0
===========
French alloy for plate, 4_s._ 5_d._ per oz.
oz. dwts. grs.
Fine silver 0 19 0
Copper 0 1 0
-----------
1 0 0
===========
French alloy, lowest standard, 3_s._ 9_d._ per oz.
oz. dwts. grs.
Fine silver 0 16 0
Copper 0 4 0
-----------
1 0 0
===========
In the preparation of these alloys with French silver it is undesirable
to make any addition of fine silver, in order to enable goods
manufactured from them to pass the Hall in safety, because the former
is assayed before it leaves the bullion dealers, and the bars of
metal are marked with their various standards. Such is not the case
in England, and refiners' fine metal is sometimes two or three grams
under what it is supposed to be; hence the necessity for the further
addition of some fine metal as we have already pointed out, when the
object in view is to have goods Hall-marked; without which addition it
cannot be effected.
In Germany there are four silver standards--one for the coinage, and
three to be employed in the manufacture of silversmiths' wares; and
in that country the various standards are severally applied in the
production of fine filigree and other artistic work. The fineness of
the standards is as follows:--
Fine silver per lb. troy.
Silver ware, 11 oz. 8 dwts. = 950 millims.
Coinage, 10 oz. 16 dwts. = 900 millims.
Silver ware, 9 oz. 12 dwts. = 800 millims.
Silver ware, 9 oz. 0 dwts. = 750 millims.
As regards the alloy to be employed in the manufacture of these various
qualities, copper only must be used, all other metals being forbidden.
These standards represent all home manufactured articles of silver
having reference to the standards of that country, as lately appointed
by law.
German pre-war coinage was the same as French and contained 36-40ths
of fine silver and 4-40ths of copper, or millesimal fineness 900 parts
of fine silver and 100 parts of copper per 1,000 parts of metal. The
highest standard of all is used for silver wares, and contains 38-40ths
of fine silver and 2-40ths of copper, or millesimal fineness 950 parts
of fine silver and 50 parts of copper per 1,000 parts of metal. The
next German standard for silver wares contains 32-40ths of fine silver
and 8-40ths of copper, or millesimal fineness 800 parts of fine silver
and 200 parts of copper per 1,000 parts of metal. The commonest German
standard employed by the silversmiths of that country contains 30-40ths
of fine silver and 10-40ths of copper, or millesimal fineness 750
parts of fine silver and 250 parts of copper per 1,000 parts of metal
indicated. Remedy 0·003.
Silver alloy for the German coinage.
oz. dwts. grs.
Fine silver 0 18 0
Copper 0 2 0
---------------
1 0 0
===============
Alloy for silver wares of the first standard.
oz. dwts. grs.
Fine silver 0 19 0
Copper 0 1 0
----------------
1 0 0
================
Alloy for silver wares of the second standard.
oz. dwts. grs.
Fine silver 0 16 0
Copper 0 4 0
----------------
1 0 0
================
Alloy for silver wares of the third standard.
oz. dwts. grs.
Fine silver 0 15 0
Copper 0 5 0
-----------------
1 0 0
=================
Silver goods manufactured according to these standards in Germany,
which have recently become law, may be alloyed only with copper, and
any foreign substance is not allowed to enter into their composition.
The remedy permitted in the actual fineness of the silver must not be
under three thousandths of the standard specified. The goods to be
stamped with the number of thousandths and the name of the manufacturer
of them, and the correctness to be certified by the firm named. Experts
are appointed by the Government to test this correctness, and if the
provisions of the law have been justly observed a government guarantee
mark is applied to them.
CHAPTER VII.[D]
Silver Solders: their Uses and Applications.
[D] See observations on Depreciation of Cost Price of Silver in Preface
to Fourth Edition (pp. vii, viii), and the new Table of Cost Prices of
Alloys in this Chapter, following the Preface (p. x).
Soldering as applied to silversmith's work is an art which requires
great care and practice to perform it neatly and properly. It
consists in uniting the various pieces of an article together at
their junctions, edges, or surfaces, by fusing an alloy specially
prepared for the purpose, and which is more fusible than the metal
to be soldered. The solder should in every way be well suited to the
particular metal to which it is to be applied, and should possess a
powerful chemical affinity to it; if this be not the case, strong,
clean, and invisible connections cannot be effected, whilst the
progress of the work would be considerably retarded. This is partly the
cause of inferior manufactures, and not, as frequently supposed, the
want of skill in the workman.
The best connections are made when the metal and solder agree as
nearly as possible in uniformity, that is, as regards fusibility,
hardness, and malleability. Experience has proved, more especially in
the case of plain and strong work (or work that has to bear a strain
in the course of manufacture), that the soldering is more perfect and
more tenacious as the point of fusion of the two metals approaches each
other; the solder having a greater tendency to form a more perfect
alloy with the metal to which it is applied than under any other
conditions. The silver or other metal to be operated upon by soldering
being partly of a porous nature, the greater the heat required in the
fusion of the solder the more closely are the atoms of the two metals
brought into direct relationship; thus greater solidity is given to
the parts united, and which are then capable of forming the maximum
of resistance. It is thus obvious that tin should not be employed in
forming solders possessing the characteristics we have just described,
for being a very fusible metal it greatly increases the fusibility
of its alloys; but when very _easy_ solder is required, and this is
sometimes the case, especially when zinc has been employed in the
preparation of the silver alloy, its addition is a great advantage
when it comes to be applied to the work in hand. Solders made with
tin are not so malleable and tenacious as those prepared without it,
as it imparts a brittleness not usually to be found in those regularly
employed by silversmiths; for this reason it is advisable to file it
into _dust_, and apply it in that state to the articles in course of
manufacture.
The best solders we have found to be those mixed with a little zinc.
These may be laminated, rolled or filed into dust; if the latter, it
should be finely done, and this is better for every purpose. Too much
zinc, however, should not be added under any conditions, as it has a
tendency to eat itself away during wear, thus rendering the articles
partly useless either for ornamental or domestic purposes earlier
than might be anticipated. Solders thus prepared also act with some
disadvantage to the workman using them, for they possess the property
of evaporating or eating away during the process of soldering, leaving
behind scarcely anything to indicate their presence; consequently the
workman has to keep on repeating the process until the connection is
made perfect, which is always done at the expense of a quantity of
solder as well as loss to the workman as regards time.
Solders made from copper and silver only are, generally speaking, too
infusible to be applied to all classes of silversmith's work.
Solders are manufactured of all degrees of hardness; the hardest of all
being a preparation of silver and copper in various proportions; the
next being a composition of silver, copper, and zinc; and the easiest
or most fusible being prepared from silver, copper, and tin, or silver,
brass, and tin. Arsenic sometimes enters into the composition of silver
solders, for promoting a greater degree of fusion; and we have heard of
workmen actually refusing to work with any other solder. The employment
of arsenic has, however, a tendency to slightly endanger the health of
those persons using it in large quantities; and of late its employment
has not been persevered in.
In applying solder of whatever composition it is of the utmost
importance that the edges or parts to be united should be chemically
clean; and for the purpose of protecting these parts from the action of
the air, and oxidation during the soldering process, they are covered
by a suitable flux, which not only prevents oxidation, but has also a
tendency to remove any portion of it left on the parts of the metal to
be united. The flux employed is always borax, and it not only effects
the objects just pointed out, but greatly facilitates the flow of the
solder into the required places. Silver solder should be silver of a
little inferior quality to that about to be worked up. The various
degrees of fusibility of the several solders are occasioned by the
different proportions of the component parts of the elements which
enter into their existence. For instance, a solder in which tin forms a
component part will flow or fuse much sooner than one in which copper
and silver alone enter into composition, or of one wholly composed of
copper, silver, and zinc, or of silver and brass; therefore it must be
understood that tin is the best metal for increasing the fusibility of
silver solders, and for keeping up their whiteness. Nevertheless it
should always be used sparingly, and even then drawbacks will present
themselves such as we have already alluded to.
It is our intention to give a list of the various solders which
have been usually employed with more or less success, so that the
silversmith and the art workman will be enabled to select the one most
suitable to the particular branch of his trade; and we contend, from
experience in the craft, that success of workmanship mainly depends
upon this point.
Hardest silver solder, cost 3_s._ 9_d._ per oz.
oz. dwts. grs.
Fine silver 0 16 0
Shot copper 0 4 0
----------------
1 0 0
================
Hardest silver solder, same as above.
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 0 5 0
----------------
1 5 0
================
Hard silver solder, cost 3_s._ 6_d._ per oz.
oz. dwts. grs.
Fine silver 0 15 0
Brass 0 5 0
----------------
1 0 0
================
Hard silver solder, same as above.
oz. dwts. grs.
Fine silver 1 0 0
Brass 0 6 16
----------------
1 6 16
================
Easy silver solder, cost 3_s._ 2_d._ per oz.
oz. dwts. grs.
Fine silver 0 13 8
Brass 0 6 16
-------------
1 0 0
=============
Easy silver solder, same as above.
oz. dwts. grs.
Fine silver 1 0 0
Brass 0 10 0
----------------
1 10 0
================
The silver solders here given are not such as we can confidently
recommend to the general silversmith, having proved them to be very
unsatisfactory in certain classes of work. For example, the first
solder, except in the case of plain strong work, would be far too
infusible to be generally used by the silversmith; the second, although
much more fusible, cannot safely be applied to very fine and delicate
wire-work, because the brass in its composition is so uncertain: unless
specially prepared by the silversmith, it probably, if purchased from
the metal warehouses, contains lead; the latter is injurious, and
in process of soldering it burns and eats away, much resembling the
application of burnt sawdust to the work. No really effective work
can be produced when the above symptoms present themselves. The same
remarks apply to No. 3, which is the most fusible, and when free from
lead or other base metal it may be classed as a tolerably fair common
solder. In the preparation of the solders to which we are alluding,
it is preferable to employ, instead of the brass, a composition
consisting of a mixture of copper and zinc, in the proportion of two
parts of copper to one part of zinc; the operator then knows of what
the solder is composed, and if it should turn out bad he will partly
know the cause, and be able to supply a remedy.
The solders that we have found to answer our purpose best are composed
of the following elements. The first is described again as _hard_
solder, but it is not nearly so hard as the one previously described.
Best hard silver solder, 3_s._ 9_d._ per oz.
oz. dwts. grs.
Fine silver 0 16 0
Shot copper 0 3 12
Spelter 0 0 12
-------------
1 0 0
=============
Best hard silver solder, same as above.
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 0 4 9
Spelter 0 0 15
-------------
1 5 0
=============
Medium silver solder, 3_s._ 6_d._ per oz.
oz. dwts. grs.
Fine silver 0 15 0
Shot copper 0 4 0
Spelter 0 1 0
-------------
1 0 0
=============
Medium silver solder, same as above.
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 0 5 8
Spelter 0 1 8
-------------
1 6 16
=============
Easy silver solder, 3_s._ 3_d._ per oz.
oz. dwts. grs.
Fine silver 0 14 0
Shot copper 0 4 12
Spelter 0 1 12
-------------
1 0 0
=============
Easy silver solder, same as above.
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 0 6 12
Spelter 0 2 4
-------------
1 8 16
=============
Common silver solder, 3_s._ per oz.
oz. dwts. grs.
Fine silver 0 12 12
Shot copper 0 6 0
Spelter 0 1 12
-------------
1 0 0
=============
Common silver solder, same as above.
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 0 9 15
Spelter 0 2 9
-------------
1 12 0
=============
The whole of the above-named solders will bleach or whiten properly if
applied to silver of the suitable quality for such purposes. We have
used copper and spelter in our silver solders, because we have found
from experience that the fewer number of times a solder is melted the
better it is for all purposes. This result of our experience is in
direct opposition to those authors who have professed to treat upon
this subject, and who can have had but a small amount of real practical
knowledge, for it is argued by them that the oftener a solder is melted
the more properly does it become mixed, and, consequently, the more fit
is it for the workman's use. To such arguments we are prepared to give
a blank denial, and our reasons for so doing we will state further on
in this treatise.
There are various other silver solders used by silversmiths; some few
of which it will be as well perhaps, while we are on the point, to
enumerate:--
Silver solder for enamelling, cost 3_s._ 9_d._ per oz.
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 0 5 0
-------------
1 5 0
=============
Silver solder for enamelling, cost 3_s._ 2_d._ per oz.
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 0 10 0
-------------
1 10 0
=============
Easy silver solder for filigree work, cost 3_s._ 9_d._ per oz.
oz. dwts. grs.
Fine silver 0 16 0
Shot copper 0 0 12
Composition 0 3 12
-------------
1 0 0
=============
Quick-running silver solder, cost 3_s._ per oz.
oz. dwts. grs.
Fine silver 1 0 0
Composition 0 10 0
Pure tin 0 2 0
-------------
1 12 0
=============
Silver solder for chains, cost 3_s._ per oz.
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 0 10 0
Pure spelter 0 2 0
-------------
1 12 0
=============
Easy solder for chains, cost 3_s._ per oz.
oz. dwts. grs.
Fine silver 1 0 0
Composition 0 10 0
Pure spelter 0 2 0
-------------
1 12 0
=============
Common silver solder, cost 2_s._ 9_d._ per oz.
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 0 12 0
Pure spelter 0 3 0
-------------
1 15 0
=============
Common easy solder, cost 2_s._ 9_d._ per oz.
oz. dwts. grs.
Fine silver 1 0 0
Composition 0 12 0
Pure spelter 0 3 0
-------------
1 15 0
=============
Silver solder with arsenic, cost 3_s._ 9_d._ per oz.
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 0 3 0
Yellow Arsenic 0 2 0
-------------
1 5 0
=============
Silver solder with arsenic, cost 3_s._ 6_d._ per oz.
oz. dwts. grs.
Fine silver 1 0 0
Composition 0 6 0
Yellow Arsenic 0 1 0
-------------
1 7 0
=============
Easy silver solder, cost 3_s._ 2_d._ per oz.
oz. dwts. grs.
Fine silver 1 0 0
Composition 0 5 0
Tinsel 0 5 0
-------------
1 10 0
=============
Common easy solder, cost 2_s._ 9_d._ per oz.
oz. dwts. grs.
Fine silver 1 0 0
Tinsel 0 10 0
Arsenic 0 5 0
-------------
1 15 0
=============
Another common silver solder.
oz. dwts. grs.
Fine silver 1 0 0
Composition 0 15 0
Arsenic 0 1 6
-------------
1 16 6
=============
A very common solder.
oz. dwts. grs.
Fine silver 1 0 0
Composition 1 0 0
White arsenic 1 0 0
-------------
3 0 0
=============
The solders here given will be found amply sufficient to select from,
for every operation of the silversmith, and will answer the several
purposes for which they have been described. When tin and arsenic are
employed in the composition of solder, either together or separately,
they should be withheld until the more infusible metals with which
they are to be united have become melted; the tin or tinsel should then
be added, and when this is well melted with the mass, fling on the
top the arsenic, let it melt, stir it well together, and pour it out
quickly into an ingot mould already prepared for its reception.
When silver and brass, or silver and composition, alone form the
component parts of the solder, these metals may be put into the
melting-pot together, well fused, stirred, and poured out as before.
Solders into which volatile metals enter, upon repeated meltings,
become hard, brittle, and drossy, and are therefore not so good as when
the metal has received only one melting; it is for this reason that
we have always preferred to manufacture our solders from metals which
have not been melted before, or from those which have gone through the
process as few a number of times as possible.
The mode of soldering gold and silver is as follows: Take the solder
and roll it out thin between the flattening rollers, or file it into
dust, according to the kind of work in hand. If filed into dust, it is
all the better if done very fine; and if reduced to a flat state, which
should be tolerably thin, cut it into little bits, or pallions, which
may easily be performed with a pair of hand-shears, length-ways and
afterwards cross-ways. When this is done, take the work which is to be
soldered, join it together by means of fine binding-wire (very thin
iron wire), or lay it upon the pumice so that the joinings can come
close together, and will not be liable to move during the process; wet
the joinings with a solution of borax and water, mixed into a thick
paste, applying it with a small camel-hair pencil; then lay the bits or
pallions of solder upon the parts to be united, and having placed the
article upon some suitable object, take your blowing instrument (Fig.
16) and blow with it, through a gas-jet, a keen flame upon the solder
in order to melt it; this will render the unification of the parts
complete and compact.
[Illustration: Fig. 16. Blowpipes.]
[Illustration: Fig. 17. Solder-dish.]
When filed solder is used, the process of charging the article is
rather different from the above. In the latter case the filings are
commonly put into a small cup-shaped vessel (Fig. 17), in most cases
the bottom of a tea-cup, or some other similar vessel, being used
for the purpose; a lump of borax is then taken and rubbed upon a
piece of slate, to which a little water is occasionally added during
the rubbing; when this solution attains the consistency of cream, it
is put into the solder-dish and well mixed with the solder. This is
then applied to the article to be soldered, by means of a charger,
consisting of a piece of round metal wire, flattened at one end, and
shaped for the purpose it has to serve. The joinings, when this kind
is employed, require no boraxing with the pencil, as described under
pallion solder; the borax being intermixed with the solder flushes
with it through the joinings to be united, thus rendering any further
application unnecessary. The process to which we are alluding is
called "hard soldering," and cannot be applied to metals of a fusible
nature; neither must it be attempted in the case of goods bearing the
name of plated, which are put together with soft or pewter solder,
similar to that used by tinsmiths and gasfitters. If there should be
any soft solder about the article, to be soldered by the means we are
describing, it would be almost certain to destroy it, the soft solder
having such an affinity for entering into combination with metals more
infusible than itself when overheated.
There is an art in soldering greater than some people would believe.
The heat required is of various degrees, some articles requiring a
broad rough flame, others a smooth one, and others again a fine
pointed one. All these circumstances connected with the process,
together with others which we could detail, proving that it is an art
only to be acquired by practice, must be considered enough; and we
proceed to observe that the skilful jeweller in soldering a large piece
of work will direct the flame of the gas jet to all parts of it, until
it is tolerably hot, and then return to the spot to be soldered, and
by a very dexterous movement of the flame, produced by the blow-pipe,
increase the heat at that spot until the solder has flushed and the
parts are rendered thoroughly secure. So far as some of the work of the
silversmith is concerned, the process of soldering is a very delicate
operation, and ought not to be undertaken by an unpractised hand.
The method of preparing solder for filigree work is worthy of a passing
notice. It is called by the Germans Lemaille solder. In the first place
it is reduced to very fine filings, mixed with burnt borax powdered
fine, and in this state it is sprinkled from a spouted grater over the
work to be soldered. The English filigree workers commonly use clean
filed solder, and by means of the camel-hair pencil apply a solution of
borax to the work, and then sprinkle the dry solder upon it from the
grater.
In Vienna a kind of powdered borax is employed, called _Streu borax_,
or sprinkle borax. It is composed of the following ingredients, which
should be gently annealed to expel their water of crystallization, the
whole well pounded and mixed together, and sprinkled over the parts to
be joined from the spouted grater as before:--
oz. dwts. grs.
Calcined borax 0 17 12
Carbonate of soda 0 1 12
Common salt 0 1 0
---------------
1 0 0
===============
The object of this mixture is to prevent the rising of the solder, and
to facilitate its flushing. Too much of it should not, however, be
put with solder in the grater at one time, as it is as objectionable
as too much borax applied in the ordinary way, but every workman will
learn from experience concerning these matters. We have tried this
mixture, prepared with filed solder in the ordinary way, and found it
advantageous at first; but its greatest drawback is the turning of the
solder yellow if not quickly used upon the work after mixing, thus
rendering the solder permanently injured. For this reason we have had
to abandon its employment in the wet state. But, in its dry state, to
the silversmith for filigree purposes it is likely to be of advantage.
It may be remarked that this preparation encumbers the work with a
great deal more flux than borax does, and consequently it requires
to be more often boiled out during the period of soldering together
the component parts. This is effected by boiling in a weak pickle of
sulphuric acid and water, composed of the following proportions: one
part of acid to thirty parts of water.
CHAPTER VIII.
On the Melting of Silver.
The processes of melting and properly mixing silver with its alloys
in a crucible are among the first operations of the silversmith, and
are, moreover, of great importance in the production of intimate and
homogeneous alloys. In order to effect these, however simple they may
appear, various precautions are necessary, and certain principles
require carrying out to arrive at the best possible results, otherwise
a great loss or waste of material may take place. To direct attention
to those principles, which from very careful attention to the subject
we have found to answer best, will first be our aim, and if we succeed
in rendering some little service to our fellow-workers in the craft
to which our toil and leisure have been devoted we shall feel highly
gratified.
The weighing of the component metals, the selection of the crucible,
the charging of it, and the attention it requires whilst in the
furnace are considerations to which we cannot too strongly call
attention. The regulations with regard to weighing should be strictly
and accurately carried out. The best and safest plan is, after the
various metals have been separately weighed, to re-weigh them, this
time collectively, in order to ascertain whether the total weight
corresponds with the previous calculation; if it does, the mixture
has been properly prepared. We have known both time and trouble saved
by the adoption of this precaution, after mistakes had occurred which
could not have been detected until the weighing of the bar of metal
had taken place after melting. There are various kinds of crucibles
manufactured for the use of the precious metal workers. Crucibles were
so-called from originally being impressed by the alchemists with the
sign of the cross. They are calculated to bear very high temperatures,
and consist of English, Hessian, Cornish, Black-lead, and Plumbago. The
last two are by far the best; the plumbago, however, being the hardest,
and capable of standing the highest temperature, is to be preferred
before all others. It will also stand more frequent meltings than any
of the rest. Such crucibles have been known to withstand the heat of
the furnace for upwards of fifty times without giving way. The wear
of them is very strong and resisting, as they only _gradually_ become
reduced in thickness, so that it is easy to distinguish their unfitness
for use. Fluxes act on earthern crucibles, particularly English at a
high temperature, whilst nitre and carbonate of soda soon destroy them.
Fluxes are necessary in most cases of metallic reductions: they protect
the metal from the air, and dissolve impurities. They are of several
kinds, as follows:--
Vegetable charcoal.
Carbonate of potash.
Carbonate of soda.
Common salt.
Sal-ammoniac.
Sal-enixum.
Saltpetre.
Borax.
Sandiver.
Yellow soap.
Black flux.
White flux.
Crude tartar.
Brown potash.
Sub-carbonate of potash.
All these fluxes have occasional duties to perform, and are therefore
of great service to the metallurgist.
To prevent the cracking or flying of the crucible, when newly employed,
it should, before being charged with the precious metal, be well
annealed; that is, heated to redness upon a very slow fire--one that
is gradually going down, and in which there is no blaze is to be
preferred, because the flame has a tendency, on the introduction of a
new crucible, to make it fly to pieces. When it has become red hot, if
a cold bar of iron be introduced it will soon show whether there are
any cracks, and if so the crucible should be rejected; on the contrary,
if it withstands this test it may be placed aside until required for
use, when it may be employed with perfect safety in the melting of
silver and its alloys.
When copper and silver only form the alloys of the silversmith, they
should both be added to the crucible at the commencement of the
operation; and it is the best plan to put the copper at the bottom,
because it is the most infusible metal. By doing so, it will receive
the greatest degree of heat, which in jewellers' furnaces always comes
upwards and the higher specific gravity of the silver has a tendency
to force that metal downwards; consequently, when the two metals have
become fused, upon well stirring--which should be done with an iron
stirrer tapered at the point, and previously heated to redness--a
perfectly homogeneous mass will be the result. When the more fusible
metals of which we have spoken are to form the component parts of the
mixture, different treatment with regard to them will be required.
They should not be added at the commencement of the operation, but
should be dealt with afterwards, in the following manner:--
Zinc is one of the more fusible metals, and is sometimes employed by
the silversmith in his alloys, for the purpose of imparting a greater
degree of whiteness to them, as well as rendering inferior silver more
easily bleached or whitened; thus assisting to bring back the natural
colour of fine silver to manufactured articles, which have partially
lost it by the addition of alloy of some other colour. Zinc, when
employed in silver alloys, should be cautiously used, and care should
be taken not to add too much to a given quantity of material. The
solder used with silver-zinc alloys should be far more fusible than
that employed with the other alloys. If too much zinc be added in the
preparation of these alloys, in the course of the work, particularly
in the process of soldering, they have a tendency to _sweat_, and
sometimes to _eat_ the metals into holes around the parts to be united;
such alloys, therefore, render this process very difficult to perform,
besides entailing more labour in the production of a clean and smooth
finish.
[Illustration: Fig. 18. Plumbago Crucible for melting.]
In melting an alloy of silver, copper, and zinc, the silver and copper
should first be melted in a plumbago crucible of the form shown in Fig.
18, and well stirred together in order that they may become properly
mixed. The zinc is sold in flat cakes under the name of spelter, and,
when required, is usually cut up with a chisel into pieces of various
weights suitable for the object in view. When the copper and silver
have become well incorporated, the mixture should be protected from the
air by a suitable flux, charcoal being the best for this purpose. The
most suitable time to add it to the crucible in the furnace is when the
metals are just beginning to fuse. This flux covers the whole of the
surface of the molten mass, and so prevents the action of the air from
destroying some of the baser metal. The charcoal should be perfectly
pure and in a finely divided state, for if adulterated with any gritty
matter (and sometimes such is the case) a very indifferent working
material is produced, the evil results of which show themselves in
every stage of manufacture. These instructions with regard to melting
the more infusible metals having been carried out, the zinc is taken
with a long pair of tongs (Fig. 19), and held within the furnace, over
the mouth of the crucible, until the temperature has almost reached the
melting point, when it should be carefully dropped into the fused mass
below, quickly stirred, so that it may become intimately mixed with the
other metals, and at once withdrawn from the furnace and poured into
a suitable ingot mould (Fig. 20). The ingot mould should be clean and
smooth inside, slightly greased, and dusted over with fine vegetable
charcoal; this latter substance prevents the metal from adhering to
the sides of the mould. It is, perhaps, almost unnecessary to state
that the ingot mould requires heating to a certain temperature before
the melted composition is poured in, otherwise serious spouting
takes place, resulting in a great loss of metal. On the other hand,
the operator should be cautious not to over-heat it, as the same evil
consequences may result.
[Illustration: Fig. 19. Tongs for Melting.]
[Illustration: Fig. 20. Ingot Mould.]
The bar of metal upon cooling should be weighed, and the difference--as
most meltings show a little--noted. This is _loss_, but it will be very
little, if the above instructions have been strictly adhered to from
the beginning of the operation. With the charcoal flux we have referred
to, very nice and clean bars of metal can be produced. This flux is
always floating upon the surface of the mixture, and, with a little
dexterity in the pouring, it can be prevented from coming out of the
crucible with the metal; its proper place is at the end of the pouring.
When tin is employed, either in alloys or solders, its treatment is
similar to that described for zinc; such alloys should not be kept
too long in the furnace after they have become fused, as they rapidly
become oxidized, especially if brought into contact with the air.
The waste in silver, and in fact of all alloys, is entirely dependent
on the duration of the time of fusion. If it is prolonged after the
addition of the fusible metals, the loss is greater in every case,
than when once melted. The metals should be subjected to the beat of
the furnace for the shortest possible period. The alloys of silver
with zinc would lose more than the alloys of silver with tin, because
zinc rapidly volatilises when heated above the temperature of its
fusion, and this is especially the case when it enters into combination
with silver and copper in the fused state; its vapours can be seen to
rise and burn in the air, producing light and white flaky fumes, and,
chemically speaking, forming the _protoxide_ of zinc. With care and
manipulative skill during the process of fusion, the proportion of
waste can be reduced to a minimum; and when this is exactly ascertained
an allowance can be made in the preparation of the mixture for the
crucible. From the above remarks it will be apparent that when both tin
and zinc form component parts of a mixture, either to be used as an
alloy or as solder, the tin should be added to the other metals, and
well stirred, so as to obtain an intimate mixture, before the addition
is made of the zinc.
Scrap silver should be carefully sorted before undergoing the process
of re-melting, and if possible all foreign substances removed. It may,
if preferred to work it in that way, be melted into a separate bar, or
otherwise used as an addition to a new mixture. When, however, it is
separately melted, a flux, such as carbonate of soda, may be employed,
on account of its cheapness, in small proportions to the charcoal flux
already alluded to. In brittle and troublesome alloys we have found
charcoal and a small quantity of borax extremely effective. Saltpetre
is a very useful flux in dissolving impurities, but in some alloys its
presence is injurious. Sandiver will remove iron or steel from the
mixture. Corrosive sublimate destroys lead and tin. We have found the
sub-carbonate of potash one of the best fluxes for silver, when matters
have not been quite so straight as they should be in the working of the
metal; it is used in melting the difficult alloy of 18-carat gold, and
is considered a secret not generally known to the trade. Sal-ammoniac
is an excellent flux for producing clean and bright ingots and tough
alloys. We invariably use it with all our alloys, mixed in small
quantities with charcoal, and prefer it to all others.
Lemel, that is the filings and turnings produced during the process
of manufacture, should have quite a separate method of treatment. It
is best prepared for the crucible by passing it through a fine sieve,
afterwards thoroughly burning it in an iron ladle, and then intimately
mixing it with a flux of the following nature and proportions:--
Silver dust 24 parts
Carbonate of soda 4 "
Common salt 2 "
Sal-enixum 1 "
----------
31 parts.
==========
[Illustration: Fig. 21. Fire-clay Crucible for Lemel.]
The sal-enixum prevents the rising of the mixture in the
crucible--which should be of the skittle shape (Fig. 21)--and keeps it
from overflowing; it also possesses a refining capacity the same as
saltpetre, and is much cheaper. The burning of the lemel has a great
tendency to destroy all organic matter that would be likely to cause
the mixture to overflow during the period of fusion; but if such a
thing should be at all likely to take place, the addition of a little
dried common salt would remedy the evil, a small quantity of which
ought always to be provided for the purpose. The common carbonate of
soda is also a cheap and useful flux to the silversmith. Five-sixths
of the above flux should be well mixed with the stated proportion of
lemel, then placed in the pot, and the one-sixth remaining placed upon
the top of the mixture, when it may at once be transferred to the
furnace. Great heat is required in this operation, and it also requires
careful supervision to prevent, if possible, waste of material. When
the mixture has become perfectly liquid, the heat of the furnace should
not be allowed to decrease, but continued for half an hour longer, and
if the use of it be not further required, the fire may then be allowed
gradually to die out. The mixture will require repeated stirrings
during the period of fusion, in order to dissolve such portions as
might otherwise not come immediately under the action of the flux.
When the operation of fusion has been completed, the crucible is
withdrawn and allowed to cool, the solidification of the metal is then
perfect, and it may be recovered by breaking the pot at the base,
when it will fall out in a lump corresponding with the shape of the
crucible. The lump of metal should then be carefully weighed, the
loss ascertained--which always varies in proportion to the amount of
organic matter contained therein; it may then be sold to the refiner,
or exchanged for new metal.
In this process it will be observed that the crucible is broken every
time a fusion takes place, consequently some little expense is incurred
in providing crucibles for the purpose. To obviate which the following
plan may be economically and successfully employed; and especially
when the metal is sold to the refiner by assay, the method about to be
described will be found most advantageous, for it should be borne in
mind that the lump of metal from the previous fusion has to be again
run down in another crucible and poured into an ingot mould before the
refiner will consent to take his assay from it. In this latter process
the whole work is performed in one fusion, and the expense of a new
crucible thereby saved. The flux employed in the reduction of the metal
is also considerably reduced. The plan is performed after the following
manner:--
[Illustration: Fig. 22. Plumbago Crucible for Lemel.]
Take a plumbago crucible of the shape shown in Fig. 22, and capable of
holding the required mixture; put the lemel into it, and then place on
the top one ounce of finely powdered carbonate of soda; this is all the
flux the mixture requires, and it is then quite ready for the furnace.
When the lemel has become properly fused, for facilitating which it is
repeatedly stirred with a thin iron rod, it is withdrawn and poured
into an ingot mould prepared for it as previously described. The flux
and other organic matter, which always accumulates upon mixtures of
this kind, is held back by the timely application of a thin piece of
flat wood to the mouth of the crucible. After the withdrawal of the bar
of metal from the ingot mould, it is cooled and weighed, and then it is
quite ready for the operations of the refiner.
CHAPTER IX.
On the Working of Silver.
Having reached a most important and very interesting part of our
subject, viz. the working of silver, and being desirous of making this
treatise useful to the silver-worker in all the branches of his art,
it is our intention to enlarge upon these processes--which are purely
mechanical--and somewhat minutely to describe the various manipulations
and arrangements required in the production of the wares of the
silversmith.
After the removal of the bar of metal from the ingot mould, it should
be plunged into a vessel of cold water, dried, and then carefully
weighed. At this stage of the process it is ready for the operation
of rolling. This process, so far as it concerns large ingots of
the metal, is a distinct branch of the trade, and is carried on in
separate premises established by certain firms for the purpose. These
establishments are called "rolling-mills," the machinery used in
them (which is powerful and costly) being moved by steam-power, the
reduction of the bars of metal to their various sizes is soon effected.
The very thin ribbon-shaped metal is produced by submitting it to the
action of rollers of smaller dimensions, one after the other, until
the desired thinness is obtained. The bars of metal are taken to these
mills by a man whose special duty it is to watch over them during the
processes of rolling and annealing, otherwise it would be very easy
to have an ingot of gold or silver exchanged for one of base metal,
the mill companies not being responsible for the material intrusted to
their care for rolling; hence the necessity for the porter's services,
to watch over his employer's interests. To prevent accidentally
exchanging the bars of metal, through their great similarity to each
other, it is the usual thing for the men in charge of them to put a
special mark upon the property of each person, previous to the process
of annealing. This mark is applied by means of a piece of chalk or
soap, and is not removable by heat. The annealing is performed in
large iron muffles, heated to redness and kept in that condition by
flues; the bars which require annealing being placed upon a piece
of sheet-iron which slides into the muffle, and there they remain
with the doors closed until they have become red hot. It is more
particularly during this operation that each person's property requires
marking and watching, because of the number of bars admitted at one
time into the muffle; and unless the greatest care be exercised at such
a time some mistake is almost sure to occur.
A register is kept of the weight of the metal sent to the mill for
the purpose of being rolled into the required shapes and sizes by
the manufacturer, who afterwards works it up into different wares
and utensils. The metal is also weighed on its admittance to the
mill, by the clerk of the works, and again on its passage out, and a
comparison of the weights registered; but in Birmingham, in some cases,
this has been so irregularly performed that great discrepancies have
actually taken place in the weights at times, and it has led to the
establishment of another rolling-mill for gold and silver, in which
the proprietors take upon themselves the whole responsibility and
care of metals intrusted to their charge for the above purpose. The
method pursued by them in respect to their business is as follows:
A manufacturer sends a bar of metal to be rolled, carefully noting
the exact weight and size to which it is to be reduced upon a proper
_order head_. This weight is carefully tested at the mill, and if
found correct, an invoice is given in exchange, upon which is entered
the cost of rolling and the time when the work will be completed. The
messenger then goes away, returning at the time stated to bring away
the rolled metal.
The advantages this system presents over the others are obvious; the
return of the full weight of the metal is guaranteed by responsible
persons, the messenger is at liberty during the time occupied in
rolling to follow his other duties, the weighing of the respective
metals is far more accurately performed both in and out of the mill,
besides greater satisfaction being given both to the manufacturer and
the roller, the reciprocation of confidence between each, being among
some of the additional advantages which might be enumerated. Messrs.
Kemp, of Birmingham, deserve the thanks of the jewellery community
for their enterprising efforts in the establishment of a system so
admirably suited to the requirements of the trade.
The following table gives the charges at the present time for rolling
bars of silver:--
Table of the Cost of Silver Rolling.
oz. oz. s. d.
Under 6 0 0 6
Above 6 and under 12 0 0 9
" 12 " 18 0 0 10
" 18 " 25 0 1 0
" 25 " 35 0 1 3
" 35 " 45 0 1 6
" 45 " 55 0 1 9
" 55 " 70 0 2 0
" 70 " 85 0 2 3
" 85 " 100 0 2 6
" 100 " 115 0 2 9
" 115 " 130 0 3 0
Above this 2s. 6d. per 100 ozs.
It is a usual thing at all rolling establishments to provide
slitting-rolls for those who choose to avail themselves of that mode
of cutting up their metal. These rolls are used for the purpose of
cutting stout bars of metal into strips suitable for wire-drawing,
thus dispensing with the older process of cutting with a pair of vice
shears, which method was slow and somewhat uncertain in the production
of good work. The slitting-rolls consist of circular barrels, after
the manner of the "breaking-down" rolls, only of course much smaller
in diameter, and with this exception, the slitting-rolls have
square grooves cut into each barrel, the projecting portion of each
corresponding with the hollow of the other, whereas the breaking-down
rolls are perfectly smooth and plain. Rollers something similar to
those we have described are used by wire-drawers to facilitate the
speedy reduction of the metal, the difference being in the construction
and action of the grooves. In the grooves of the latter, which are
inserted farther apart, the hollows take a half-round shape, and unlike
the slitting-rollers, during the revolution of the barrels, the grooves
in this case directly meet each other, and thus produce a strip of
wire almost round. It is almost needless to remark that wire-rolling
requires some amount of practical knowledge to perform it properly.
The manipulations indispensable to the art of silver working are so
varied and so numerous that we are at a comparative loss which part of
the process to consider first; however, if we follow the course of the
workman with regard to the production of the various manufactures of
his art, we shall perhaps not be far wrong in our desire to effect the
purpose we have in view.
In commencing to enlarge upon these mechanical processes we may at once
state that it is our intention to refrain from going into the whole
art of wire-drawing, because that process has been somewhat minutely
alluded to in our other work recently published in the interests of the
goldsmiths; the details of which are there fully described.
[Illustration: Fig. 23. Draw-plate.]
The draw-plate, Fig. 23, which is the principal tool of the modern
wire-drawer, was unknown in this country until the middle of the
sixteenth century, when it was introduced by Christopher Schultz, a
Saxon, from France. It was supposed to have been the invention of a
native of that country named Archal. The draw-plate had been in use
some years on the Continent previous to its introduction into England.
The old method of making wire was upon the anvil, by means of the
hammer; and those who manipulated in this art were termed wiresmiths
at that period. The best form of draw-plate consists of a piece of
steel about nine or ten inches long, one and a quarter to one and a
half inch broad, and about half an inch thick, each containing a number
of conical holes of various sizes, becoming smaller in succession
until the last hole in the plate is reached, when another plate,
corresponding in size, having smaller graduated holes, is employed, and
the wire drawn through it; and so on, until the proper size has been
obtained.
[Illustration: Fig. 24. Draw-bench for Wire.]
[Illustration: Fig. 25. Draw-tongs.]
[Illustration: Fig. 26. Drum used by wire-drawers.]
[Illustration: Fig. 27. Skeleton Frame or Swift used by wire-drawers.]
The drawing of stout pieces of wire is effected very readily by means
of the draw-bench (Fig. 24), and the thinner pieces, by the application
of draw-tongs (Fig. 25), held in the hands of the operator, and made to
do service by swinging the body backwards. Very fine wire is now drawn
by means of an apparatus called a _drum_ (Fig. 26), revolving upon a
perpendicular pin, the exterior of which receives the wire and prevents
it from becoming entangled. When the end of the wire has finally passed
through the draw-plate, the whole coil is carefully removed from the
drum (which is made slightly conical in form for facilitating the
process) and placed upon a skeleton frame made to receive it (Fig. 27);
it is then in proper form for its passage through the next hole of the
draw-plate.
In the production of very fine wire, the metal, after passing a few
times through the draw-plate, requires annealing, as its fibres become
so condensed and hardened that it is impossible to repeat the operation
without some risk of the wire breaking. For fine wire the annealing is
repeated five or six times during its passage through the draw-plate;
for stouter kinds the annealing need not be so frequent. This process
produces a scale or oxide upon the surface of the wire, which should
be removed before the continuation of the drawing takes place, which
is generally done by an immersion for a time in very dilute sulphuric
acid pickle; or its passage may be assisted through the draw-plate by
the application of some lubricating substance, such as beeswax, or
a mixture of beeswax and oil, which enables it the more readily to
pass through it. In the progress of the wire-drawing the holes have a
tendency to become enlarged; these are made smaller again, by repeated
blows upon the front of the plate with a somewhat pointed hammer (Fig.
28), and then opened from the back with a tapered steel punch, such as
is shown in the woodcut (Fig. 29). The hardening and tempering of the
punch is of importance. A gauge-plate is used in all establishments
for the purpose of determining the size of the wire. The hammering
should not take place upon a hardened draw-plate, as it would fly
to pieces: it is only those known as soft which should receive such
treatment; and those, by a continual alteration of the holes, gradually
become hard and require annealing at intervals.
[Illustration: Fig. 28. Knocking-up Hammer.]
Draw-plates for wire-drawing purposes are mostly cylindrical in form,
but they are employed in various degrees of fineness and in different
shapes; such as oval, oblong, half-round, square, fluted, star,
sexagon, triangular, and other complex sections, for the production of
corresponding wires, all of which receive similar treatment to that
above described.
[Illustration: Fig. 29. Round Steel Punch.]
The process of wire-drawing, in connection with the art of the
silversmith, is more particularly employed in the manufacture of
chains, in which branch a very large quantity of silver is consumed.
This branch of the craft is almost a purely mechanical one, but,
nevertheless, there are some designs in chains which require a
considerable knowledge of art for the proper execution of them. It
is, however, in "wrought" or hand-made work that true art is made to
play so conspicuous a part; for it is here that perfect workmanship,
together with great skill and taste, are required in the manufacture
of an article. "Wrought" work was one of the earliest productions of
the goldsmith and silversmith, and it still remains the true _artistic_
method, although it has been superseded by others of a less expensive
character; such as stamping, chasing, engraving, enamelling, casting,
&c., to which the older processes of ornamentation and decoration by
means of hammering have given place.
[Illustration: Fig. 30. Hammer for Wrought Work.]
[Illustration: Fig. 31. Sparrow-hawk.]
Wrought work is produced by hammering and soldering the various pieces
or ornaments together; and one of the very first things to be attended
to in the production of this kind of work is proportion, a knowledge of
which is indispensable to true art-workmanship; for the piece of metal
which is to be operated upon by the hammer should be of the proper
size, so as to require none to be cut off afterwards. Every portion
of a design should be wrought out of the piece of metal separately,
and soldered in its proper place upon the article in process of
manufacture. When circular forms have to be raised or flanged by the
employment of the hammer, as in the case of a raised or flanged brooch
"bezil," the _modus operandi_ is as follows:--Take a piece of metal
of the exact size and shape, turn the two ends together from the
longitudinal direction, and unite them by soldering; when this is done,
the circular band of metal is taken and flanged by means of the hammer
and a miniature anvil, placed upon a stout piece of wood which the
workman renders secure by placing between his knees, the pressure of
which retains it steadily in its place during the various manipulations
performed upon it; this kind of tool is termed a "sparrow-hawk"--a
representation of it is given in Fig. 31. The work is effected by a
series of blows dealt with the hammer in regular concentric circles,
the bezil all the time gradually working round the pointed end of the
sparrow-hawk. It requires great skill and practice to produce the
proper shape, and to keep all parts of the metal of equal thickness.
The bezils may be produced in this manner round or oval, as well as
other complex shapes; the hammering taking place according to the shape
required. When raised or ornamental brooch bezils, such as concave or
convex patterns, are to be made, the means adopted in their execution
are somewhat more complicated than the mode of flanging above alluded
to. A tool called a "swage" is employed, which partakes of many forms,
the pattern or ornamental device which the metal is required to take
being the shape of the swage, or otherwise cut upon it. The metal is
easily raised to take the proper design, by a very careful application
of the hammering process.
Sometimes in silver-working the form of the object to be manufactured
is of such a nature as not to allow of the use of the swage tool, and
this is more particularly the case in the manufacture of plate. Such
things, for instance, as cups or tankards which have raised ornamental
surfaces, and which have to be executed after the vessel is roughly
finished, require altogether a different tool for the effecting of such
purposes. The one commonly employed in operations of this description
consists of a bent piece of steel, upon one end of which is cut the
device required; this end being turned up to the required height
for raising the design, and the other end being bent in an opposite
direction, which, when required for use, is secured in a vice. The
workman, in executing the design upon the object in hand, places it
upon the "snarling-iron" (for such the tool is called) at the part
to be raised, and there holds it securely while another man strikes
the piece of steel at the top of the angle, or just above where it is
secured in the vice, the reaction of the steel wire then throws out
the metal, in accordance with the device or pattern cut on the end of
it. Designs are only roughly raised in this manner, the perfecting of
them being performed by the application of various kinds of chasing
tools. To prevent a change in the form of the object undergoing this
operation, it is filled with a composition formed of pitch, resin, and
brick-dust, in the following proportions:--
Pitch 4 parts.
Resin 4 "
Brick-dust 2 "
---------
10 parts.
=========
The preparation of the cement is as follows:--Reduce the brick-dust to
a very fine powder, and pass it through a fine sieve; then take the
other ingredients and melt them in an iron ladle or other suitable
vessel over a slow fire, stirring them well together; when this has
taken place, the mixture will present a thin liquid appearance, which
is the time for using the brick-dust. This should be added in small
quantities at a time, and well stirred together, until the mass has
become tolerably thick. It is then poured out either upon the floor, or
into some suitable vessel provided for its reception. While undergoing
the operation of chasing, the lower part of the object is preserved
from injury, by being laid on a sand-bag. The illustrations, Figs. 32
and 33, represent the snarling-tool, and its mode of application to the
work of the silversmith.
[Illustration: Figs. 32, 33. Snarling-tool, and its mode of application
for raising.]
The progress of the silversmith's art, in conjunction with the
researches and discoveries in the mode of working the precious metal
during the past century, have wrought a great change both in the
style and manner of workmanship. Before the period referred to, the
gold and silversmiths' trade was in its lowest possible condition;
partly, no doubt, on account of the war then raging on the continent
of Europe, and partly because the silversmith at that time was not
allowed to manufacture articles of any standard inferior to that of
the coinage of 11 ozs. 2 dwts. Until the peace of Waterloo, few people
were busy but the gun-maker, and other smiths who were able to work
at similar occupations; but with respect to most other trades, the
men did all they were capable of, in order to earn their daily bread.
If at that time the silver trade had been specially cultivated, the
art, as regards its progress, would have met with many drawbacks, as
compared with the present time; the knowledge of the workmen in the
production of finished work was not equal to that to be found upon
the best articles now manufactured. And although forbidden by law to
work in inferior metal, they would have been incapable of effecting
the beautiful surfaces which modern articles of inferior quality are
made to present. The recent scientific discoveries, both chemical and
mechanical, that have taken place during the last sixty or seventy
years, have wrought a great change in the general conditions, as well
as in the mode of the manufacture of silver wares.
We have said that previous to the year 1815 all was dark and obscure
with the precious metal worker, but from that period the work gradually
rose in artistic excellence, and the trade very slowly improved;
the cause of this no doubt being due, in a great measure, to the
security afforded as the result of peace, and with it a revival of the
industrial occupations. With the increased industries of the nation
arose the pleasures and pastimes of the people, and racing became a
national sport. This kind of pleasure soon led to an increase in the
work of the silversmith, in consequence of the demand for racing cups,
which gave opportunities for the artistic excellence of design in
their manufacture; and the silversmiths who made them soon acquired
a prestige as Art-manufacturers. The demand for work of that and a
similar kind led to the employment of regular designers and modellers,
who gradually improved both the designs and the work in different parts
of the country.
At the period of which we are speaking, polished or burnished silver
goods were most in demand, the modern processes of surface finishing
not being then understood. The introduction of the French style of
work in filigree soon afterwards caused a demand for that class of
work; and the attention of those in the trade was then turned in that
direction for a time, and others springing up, the silversmith's and
goldsmith's trade generally began to assume a position of importance.
This kind of work required no polishing and very little artificial
finish; besides being exceedingly light in weight and graceful in
appearance. It required fine material for its manufacture. In England
filigree work has been superseded by other processes, but in India, and
in other parts of the East, it is still cultivated to perfection.
Silver and gold filigree is also manufactured in the Ionian Islands,
in Switzerland, and in some parts of Germany and France, where labour
is cheap. In the two latter countries it is made from a very inferior
material to that used in India. Silver filigree work in this country
was soon found not to answer all the requirements of modern society,
so far as regarded its utility, durability, and cheapness; fashion
therefore demanded something different. It is worthy of remark that
while this class of jewellery in both gold and silver was so much
in vogue for ladies' wear, the old-fashioned seals and keys had
undergone a change, and the chasing of them in representation of
filigree ornamentation had become the fashion for gentlemen's wear.
The processes of the manufacture of filigree wire and its mode of
application to the work of the artist, have been considered in a
previous chapter, further detailed information is therefore rendered
unnecessary.
[Illustration: Fig. 34. Die.]
When filigree work was no longer used, the fashion changed into
"stamped" or "struck-up" ornament. Small pieces of metal were struck-up
by means of the hammer and punch, or by the use of the hand-press or
stamp; in the former case a lead cake would be prepared, composed of
a mixture of lead and tin, and upon it the various ornaments would be
produced from the flat metal, corresponding with the pattern of the
punch employed for the purpose; in the latter a small die (Fig. 34)
would be employed with the pattern sunk upon it; this would have an
aperture through it, the dimensions of the off-side being generally
rather large, gradually becoming smaller towards the front surface,
which takes the form, in general outline, of the desired pattern. When
the necessary blanks have been cut out, another die and punch are used,
by which they are raised to their proper shape. These tools should be
firmly secured in the press (Fig. 35), otherwise they are likely to be
soon destroyed.
[Illustration: Fig. 35. Press.]
The small ornaments thus raised were variously arranged one upon
another, until a design or pattern was formed, which in every way
appeared very showy. Such articles suited the tastes of the people at
that time, and still suits those who require good weight for their
money. The same kind of thing existed at that period in chains, and
being heavy-looking, and costly in appearance, they attracted attention
and caused a demand. Thus with the continual changing of the fashions a
new era for the goldsmiths and silversmiths of England began. They were
beginning to work in all sorts of qualities, with the manipulations
and finish of which they were becoming now thoroughly conversant,
and a demand springing up for goods for purposes of exportation,
encouragement was given to the trade, which soon assumed the position
of a thriving industry.
The style of work that followed the "struck-up" patterns was that of
plain and solid silver-work, well polished and whitened. This sprung up
about the period when coloured gold became the fashion, and the mode
of finishing it being somewhat similar, no doubt the demand arose as
much from the introduction of colouring as from any other assignable
cause. In the chain-maker's branch of the art, a great variety of new
patterns came into existence at this period; chain bracelets also began
to be introduced; and altogether the trade made rapid strides, and fast
rose into a great commercial industry. This kind of work has remained
more or less in fashion up to the present time, and vast quantities of
silver chains of the plain and solid patterns are now being made in
Birmingham.
The silver trade seems to be an exception to the general depression
which now prevails in all the other branches of the jewellery trade;
the fashion just now is for silver, which causes a greater demand
than is usual for goods manufactured of that material. In a short
time we believe this fashion will undergo a change, and then no doubt
manufacturers who have taken advantage of it to make large stocks will
have goods remaining upon their hands which they will not be able
readily to dispose of, unless at a sacrifice; for it should be borne
in mind, that to keep a large stock of silver goods in a saleable
condition, and without a quick sale, considerable expense is entailed
above the cost of making, to keep them in that condition, through
their great liability to become tarnished.
After the introduction of plain and solid-looking work, it next became
the fashion to have it chased over its entire surface. Following this,
about the year 1825, came the beautiful process of enamelling, which
added artistic beauty to the work, and brought out the harmonies of
colour. About this time, too, there sprung up a great demand for the
so-called "galvanic ring," which consisted of a lining of zinc and one
of silver. The ring represented, in appearance, those large, plain,
half-round rings which are now made in 18-carat gold, and which weigh
from 7 to 10 dwts. each. It was then as now made of half-round shape,
and sometimes with the addition of a buckle upon it. The silver was so
drawn upon the zinc that the outer surface appeared entirely of silver,
and a portion of the inner surface was made to show the zinc only,
which was quite sufficient for the purpose required. When the ring was
put on the finger the zinc, in conjunction with the silver, touched the
flesh of the wearer, and was thus supposed to create a galvanic action,
which it was alleged had a tendency to remove or prevent _rheumatism_.
This kind of work had a good run at the time of its introduction, but
like all the rest, the fashion lasted only for a while, when something
else had to be brought to the front in the silver trade. The mode of
the preparation of the wire was as follows:--A bar of silver would
be rolled out until a certain thinness was attained, occasionally
annealing it during the process; it was then cut into strips wide
enough for the purpose required, again annealed, and subsequently
doomed. The latter process was effected in this manner:--A block of
hard wood, such as boxwood, would be made use of, having a round groove
in one side of it, the metal to be doomed would be laid along the
groove and a round piece of iron or steel held upon the upper surface
with the left hand; a wooden mallet is then taken with the right hand,
and by a skilful application of it to the piece of iron or steel, the
metal is soon forced down in the groove and made to take the proper
form for drawing. The flat strip of metal should be pointed; this may
either be done before or after the dooming process, though it commonly
takes place before. It is performed by taking away a small portion in
a conical form, from one of the ends with a pair of hand-shears. A
piece of zinc wire should be provided, corresponding in shape with
that the ring is to take; this is placed in the hollow of the silver
to be drawn, with the flat side outwards, so as to correspond with the
aperture in the plate through which it has to be drawn. A draw-plate
is then taken, with holes of the half-round shape, and the two metals
carefully drawn through them. The drawing through a succession of holes
produces an edge upon the silver coming against the flat side of the
aperture in the draw-plate which overlaps the zinc and thus holds it
securely in its place.
[Illustration: Fig. 36. Hammer for dooming.]
A change in the style of work gradually took place in the course of
every few years, and thus it was that hollow-work became the fashion.
This kind could be made in a variety of ways, and being very light
and showy, it appeared much more expensive than it really was. It is
therefore very easy to account for the changes which have taken place
in the manufacture of articles of adornment and luxury, and for the
encouragement which the art has received. With the present styles of
the "plain," the "solid," the "filigree," the "stamped," the "mosaic,"
the "cameo," the "repoussé," the "inlaid," the "enamelled," and a
variety of others, we can fearlessly say that silver-working has of
late years made rapid progress, and attained to a higher standard than
it ever before possessed.
[Illustration: Fig. 37. Steel Die.]
[Illustration: Fig. 38. Stamping Press.]
The art of stamping and shaping articles of jewellery from sheets of
the various metals came into general use just previous to the first
Exhibition in 1851. These, which are made in considerable numbers,
are produced by means of dies, having the shape of the pattern upon
them, both at the top and bottom, made of hardened steel. Fig. 37
represents a bottom die for the use of the stamping press, and Fig. 38
represents the press. In raising the metal by stamping, the material
undergoes the same bendings and extensions between the dies as if it
were being manipulated by the hammer, and consequently it requires to
be repeatedly annealed, otherwise it would crack and fall to pieces in
a subsequent operation. The raising should be brought about gradually,
and this is done by placing a number of sheets of metal between the
dies, which prevents the top die from falling with too sudden an action
upon the metal, which it would do, as it falls with a succession of
forces if the process be repeated, and if its action be not arrested
by the means we have pointed out. After every blow of the stamp one of
these pieces is removed from the bottom, and a fresh one added at the
top; the continual falling of the stamp gradually forces these plates,
if placed in the manner we have indicated, to take the shape of the
die. The exact form of the figure is effected by striking the plates
singly between dies which exactly correspond. A very large quantity of
work is now produced by the means we have stated, such as brooches,
studs, locket-backs, earrings, rings, and an endless variety of other
things; moreover, by the cultivation of this art a considerable amount
of the labour formerly bestowed by hand upon the work is now saved, as
the stamping in many instances is so complete, almost taking the form
of a finished article after that process has been performed, that the
workman has only to arrange the parts and supply the ornamentation when
required, to render the article complete.
Works of art are also produced by other methods; as an example, we
will take the process of "spinning or burnishing into form," which
consists in spinning the metal to the desired shape in a lathe, by
means of burnishing tools, specially made for the purpose. This
process is employed in the production of large bangle bracelets with
plain surfaces and other similar works. The metal to be operated upon
should be soft and malleable, otherwise the process is very difficult
to perform. The disc, or other form of metal, is taken and fixed in
the lathe with the aid of holdfasts, a chuck or mould of the desired
pattern being provided, upon which the disc is turned by the tools
referred to. The metal, as in the other processes, is _gradually_
spun into the required form. In most cases the mould is exactly the
shape of the interior of the article required to be made, and under
these circumstances it would be made up in several pieces together
with a key-piece; so that when this latter is taken away, there is no
difficulty in removing the rest, and leaving the article free. It is of
importance, during the spinning, to keep the edges free from notches,
but should these occur, it would be better to touch them a little with
a turning tool. The metal for spinning into a bangle bracelet should be
of the form of a flat circular band, soldered of course; it would then
be secured upon a properly shaped mould, composed of several pieces,
in the manner above described; this would then be placed in the lathe,
and the application of the spinning tools would soon bring about the
desired form. After the removal of the spun piece of metal, the workman
trims the edges up a little, then saws it into two pieces, and at once
proceeds to the operations of snapping and jointing, which are delicate
processes to perform properly in work of this kind, and require the
services of a skilled and competent workman.
Having now described some of the processes in the working of
silver, and alluded to the various articles which are produced by
_wire-drawing_; _raising_ with the hammer; _stamping_; _spinning_;
_chasing_, &c.; we shall next direct attention to those processes which
immediately come after the putting together and soldering the article;
and foremost of these is _polishing_. We trust that the foregoing
details in reference to this part of the subject will convey some idea
of the art of silver-working.
Polishing is an important process With all precious metal workers.
It is applied for the production of _surface_ to their wares, and in
proportion to the smoothness required upon the work, so should be
the fineness of the material employed in effecting it. The polishing
powders are _emery_, _powdered pumice_, _crocus_, _rottenstone_, _putty
of tin_, and _rouge_. In the best work, scratches are removed with a
smooth and rather soft dark grey stone (Water-of-Ayr stone); it is
then polished in the lathe with a stiff brush, and the application
of a little fine polishing mixture. We have placed the materials
for polishing in their respective order of smoothness or fineness,
beginning with emery, which is the coarsest. A very good mixture for
ordinary work consists of equal portions of emery, pumice, and crocus,
with oil added to the consistence of a thick paste. Good work does not
want much polishing, for the beauty of it depends _more_ on its being
executed by a well-trained workman; whereas rough and badly executed
work requires much polishing, and for this the coarser powders are
preferable, or a mixture of them; but for the smoother work the finer
powders should be employed.
The Water-of-Ayr stone employed for polishing is usually obtained in
the form of small square sticks, and is used with a small quantity
of water to the surface of the work, in a similar manner to filing.
The stone is softer than the material upon which it operates (and, in
fact, so are all the materials for polishing), and therefore wears
away, producing a mud-like substance upon the article, which should be
repeatedly removed in order to ascertain the progress made. This may
be done with a piece of clean rag, or tissue-paper. When the work is
polished at the lathe it will gradually become enveloped in grease,
&c., which should be removed occasionally, to show when the process
has been carried far enough. The polishing of silver work is a branch
of the trade commonly performed by girls. It is hard work for them, as
the metal possesses a very soft nature; it therefore pulls hard against
the brush which holds the polishing mixture. The lathe employed is the
ordinary polishing lathe with a horizontal spindle, and is worked with
a common foot-treadle; steam-power is used by some firms for moving
these lathes, but it is by no means the usual custom at present.
After the completion of the polishing process, the work is well washed
out in a prepared solution, to remove the mixture which adheres to it;
a solution of soda is found to answer the purpose best, both from its
cheapness and effectiveness. It should be used hot, with the addition
of a little soap, and with a stiff brush the dirt is soon removed. The
quantity of soda used to a given proportion of water differs in the
trade, and there is no set rule to go by; it depends, more or less,
upon the adhesiveness of the polishing mixture. We have found about two
ounces of it to a quart of water amply sufficient for the purpose.
CHAPTER X.
Enriching the Surfaces of Silver.
By the application of the processes about to be described, the
finishing touches in their relation to articles or wares of silver
manufacture are effected. These processes, as adopted by the trade,
are various, almost every firm having a specially prepared mixture and
mode of employing it. We shall refer only to those which, from their
practical utility, are likely to be of service to those workmen who
have to do with this particular metal. The branch of the art of which
we are now treating comes only into operation when every other process
of workmanship has been completed; and some of these processes must be
executed in a perfect manner in order to arrive at the highest possible
results in this one. The best and richest surface is produced when the
metal to be operated upon is good in quality, and the workmanship of
a fair order, so far as regards smoothness, and freedom from surplus
solder-marks.
One of the oldest methods for producing a pure snowy whiteness upon
articles of silver was as follows:--Take an iron or copper annealing
pan (the latter is much to be preferred), place the work upon it in
proper order, so that it may be heated all over alike. It should,
previous to this, be immersed in a thick solution of borax, or
otherwise brushed over with it. After the work has been properly
arranged upon the pan for annealing, it must be sprinkled over with
fine charcoal dust; the pan is then placed in the muffle upon a bright
clear fire without blaze, and when the work has assumed a degree of
heat approaching to cherry redness, it is withdrawn and allowed to
cool. When this has taken place, it is removed and boiled out in a
very weak solution of sulphuric acid, commonly called oil of vitriol.
If the right colour was not then produced, the process was repeated
as many times as circumstances permitted, though usually two or
three times was found to be amply sufficient. The annealing process
required great attention, for the work being in contact with borax,
if slightly overheated, it was liable to become melted, therefore the
operation was a delicate one to perform, and was only intrusted to
such workmen as were experienced in the art. Small delicate articles
were commonly treated with the mouth blow-pipe and gas-jet, and were
placed upon a pumice-stone, or some other suitable substance capable
of withstanding the power of burning. According to the inferiority
of the silver alloy, is the difficulty of producing a good white
surface on wares of such standards. Fine silver requires very little
whitening, generally one process suffices to effect a good colour;
but inferior standards require half a dozen or more to bring up the
proper degree of whiteness; and those ranging below 9 oz. 12 dwts. to
the lb. Troy cannot be whitened at all by the means we have described,
but require the application of the modern chemical process, known as
electro-plating.
The East Indian silversmiths never touch their manufactures with
any kind of abrasive substance, from the most delicate, to the more
strongly made article. But then it should be remembered, that in India
the natives work from the pure material, a point which they rigidly
adhere to; whereas we are compelled in this country to manipulate in
all sorts of qualities; and some of these require no little trouble
and difficulty to bring back to the surface the snow-white appearance
of the pure metal. In the former case it is effected without any
difficulty whatever--in fact, the metal scarcely undergoes any change
throughout the whole of the manipulations to which it is subjected in
the various processes of manufacture. The Indian mode of procedure is
as follows:--Some juicy lemons are cut into slices; the silver articles
are briskly rubbed with these for a short time, and subsequently
covered with them, being placed in a suitable vessel for a few hours
for the completion of the process. For very delicate articles of
jewellery the natives cut a large lime nearly in two halves, into which
they insert the work; the halves are then tightly closed up again, and
placed aside for a few hours; when the article is removed, it is well
rinsed in clean water, and consigned to a vessel of nearly boiling
soap-suds, where it is well brushed, again rinsed in fresh hot water,
and finally dried on a metal plate placed over hot water; the process
is rendered complete by a little gentle rubbing with wash-leather if
the work be of a plain nature. Green tamarind pods are also employed
by them for the purpose of whitening silver, in the same manner as
just described; they are great detergents both of gold and silver
manufactures, and are largely employed by artisans in the East for the
removal of oxides and fire-marks.
Another process for the whitening of silver goods is performed in the
following manner:--Take the work, which must be cleanly prepared, and
give it a coating of the following mixture:--Finely powdered vegetable
charcoal four parts, saltpetre one part; the ingredients should be
well mixed with a little water, and may be applied to the surface of
the metal either by brushing over with a soft brush, or by dipping
the work into it. The work is then placed upon the annealing pan and
submitted to the heat of the muffle, until the wet powder has become
perfectly dry and ceased to fly about; it is then withdrawn from the
muffle, allowed to cool, and afterwards boiled out in a solution of
potash prepared for the purpose, in the proportion of about one ounce
of bi-sulphate of potash to twenty ounces of water. The boiling out
is done in a copper pan (Fig. 39), and if the work be put through the
above process two or three times a beautiful dead-white colour is the
result. It is then washed in a hot solution of soda, soap, and water,
or if preferred bright, scratched, or burnished, and the process is
finally completed by drying it in fine boxwood sawdust, which should
be made hot, but not allowed to char or burn in any way, as it would
produce a stain upon the work very difficult to remove, and thus the
finish would be considerably impaired.
[Illustration: Fig. 39. Boiling-out Pan.]
In large manufactories the process of whitening silver goods is
repeatedly required to be performed, and where such is the case, the
above methods are found not only tedious and expensive, but occupy much
unnecessary time and labour; to dispense with a portion of which, the
custom of covering the work with a chemical preparation was accordingly
departed from, and yet it was made to show its former brilliancy.
To effect this object the liquid for boiling it in was differently
prepared, which only required to be made of a proper strength to do all
that the surface mixture had done before. The following is the method
adopted in preparing the cleansing liquid. Boiling-out mixture:--To one
pound of smoking salts, add two ounces of cream of tartar; well shake
the ingredients together, so that they may be thoroughly incorporated.
The smoking salts employed for this purpose are not the ordinary
_spirits of salts_ of commerce, but a preparation of the common oil
of vitriol; therefore the one should not be taken for the other; the
spirits of salts would turn the work black, whereas, if the proper
ingredient were procured, a fine dead matte or blanched surface would
be the result of its application. The mixture employed for boiling
the work in consists of the proportion of one ounce of the above
preparation to about thirty ounces of water. The silver articles
simply require to be annealed, allowed to cool, and then boiled for
a minute or so in this solution, when the desired result will be
attained; if, however, the exact colour be not obtained the first time,
the process should be repeated a second, and if necessary, a third
time; the right colour will then be produced, if the articles are not
made of a too inferior standard.
The mode we have ourselves adopted for the colouring or whitening of
silver goods is somewhat different, and still more simple than even the
above. We will proceed to give the details of the process. A mixture
of very dilute sulphuric acid is first provided, in the proportion of
one ounce to forty ounces of water, and well mixed together; the work,
after being heated to a good red heat, is boiled in this, which soon
removes the oxide from the surface, and shows the fine white colour of
the pure silver. For fine silver work, such as Indian filigree, one
process will generally suffice, for English standard quality two, and
for low qualities three, but these latter must not by any means be too
low; if so, no colouring can take place by the method just described.
Objects of delicate workmanship are usually annealed by the gas; being
placed on a pumice-stone of light material, the flame of the gas
is blown with the mouth blow-pipe, in such a manner that the object
gradually becomes heated all over alike; and the work should be well
heated, as this facilitates the process of oxidation, and subsequently
that of whitening. The oxidation takes place at the expense of the
copper in the silver alloy, and this is only effected by raising the
articles to a very high temperature, which produces the oxidation of
the copper coming in contact with the air, and which necessarily exists
upon the surface of the alloyed goods. Whitening silver goods then
is nothing more than the removal of the base alloy from the surface,
leaving the pure metal behind with its full rich colour. Therefore to
be clear, the process of annealing in contact with cold air oxidizes
the copper upon the surface, and the pickling mixture so dissolves and
removes it, that it gradually undergoes a process of refining, and is
ultimately made to represent the finest material in all its purity.
Sometimes silver work is to be seen having a brown colour upon it;
this is produced when the acid employed for cleansing has been too
strong; it can only be remedied by another annealing and boiling-out in
a much more diluted mixture. There are various other methods employed
in the trade for the purpose of whitening silver work of the best
quality; and although annealing is always a part of the process, other
ingredients, such as salt and tartar, permanganate of potash, cyanide
of potassium, alum, &c., have been severally used for the cleansing or
whitening mixture. They may be useful in their application to plated
work (articles that have received a coating of pure metal by means of
the electro-metallurgical process), for cleansing purposes only, but
for all practical purposes the process to which we have called special
attention is to be much preferred.
Common articles of silver cannot be whitened by annealing and
boiling-out in a diluted acid; a thin film of pure silver must be
deposited upon their surface by the process of electro-deposition,
or by the action of some chemical preparation in which fine silver
forms the principal ingredient. Such preparation, however, as the
latter can be used only to plain surfaces, therefore they are not
applicable to all kinds of work. They are composed of the following
chemical ingredients:--1st, chloride of silver 1 part, cream of tartar
1 part; 2nd, chloride of silver 1 part, common salt 1-1/2 parts; 3rd,
chloride of silver 1 part, prepared chalk 1 part, pearl-ash 1 part;
4th, chloride of silver 1 part, alum 1 part, common salt 2 parts. The
chloride of silver is easily prepared by precipitating it from the
nitrate with a solution of common salt or hydrochloric acid. The
various mixtures should be worked up with water into a thin paste,
and applied to the work by rubbing with a soft cork or piece of
wash-leather, or by thoroughly stirring it about in the mixture until
it has acquired the requisite degree of whiteness. For the purpose of
silvering watch and clock faces, &c. these mixtures may be used with
advantage and entire success.
Other solutions are sometimes employed for similar purposes and are
very useful; being simple in their preparation and easy of management.
We have selected the following as being the most practical:--Take one
ounce of the _nitrate_ of silver and dissolve it in one quart of pure
distilled water, or if this cannot be procured, water which has been
boiled, by which it loses some of its impurity. When the nitrate of
silver has become thoroughly dissolved, throw into the mixture a little
powdered hyposulphite of soda, this will precipitate the silver, and
when it has taken place, a further addition of hyposulphite of soda
should be made, which will eventually re-dissolve the precipitate, and
the solution is then ready for use. To produce a good mixture, the salt
of soda should be added slightly in excess. The solution is used by
simply dipping a sponge in it and rubbing it over the surface of the
articles to be coated, and this is continued until they have assumed
the desired colour.
For improving the colour of silver and electro-plated wares, the
following mixture has been strongly recommended:--Nitrate of silver
4 pennyweights, cyanide of potassium 5 ounces, and water 1 quart;
the ingredients should be well mixed together, and applied by means
of a soft brush or sponge to the surface of the work. In using this
cyanide solution, the operator should be careful to guard against a too
frequent contact with it, as it is decidedly injurious to the hands,
especially if there be any abrasion of the skin; it being one of the
deadliest poisons known. Sufficient details of the process of silver
whitening and cleansing having now been given to assist the workman
who manipulates in this particular metal, and to enable him to select
a form of recipe in every way adapted to the kind of work in hand, we
shall now proceed to the modern process of _electro-plating_, and give
a practical description of it in its applicability to the trade of the
silversmith.
This art is decidedly of modern origin, as far as concerns its
employment for commercial purposes. The invention is supposed to be
due to the electrical and chemical researches of Mr. Spencer, of this
country, and Professor Jacobi, of Russia, both of whom claim to have
found out the art of depositing one metal upon another, somewhere about
the same period. Of course it was left to others to apply the invention
to the industrial arts, and it was not until after the discovery of the
_Constant Battery_, by Professor Daniell, about half a century ago,
that the art began gradually to extend in the direction of commercial
pursuits. The Messrs. Elkington, of Birmingham, were the first to
employ it in their manufactures, with a success which their enterprise
thoroughly merited. This took place about the year 1840, and since that
time the art of electro-plating and gilding has wonderfully developed,
in its application to the various manufactures of the country. Its
progress would be a subject highly interesting, were we to trace the
general details of it, but the part of it we are considering being the
practical mode of its employment in manufactures, we shall at once
direct our attention to it, by giving a complete description of the
process; so that the ordinary silversmith may be enabled to employ it
in his business with safety and advantage.
The first thing to be considered in electro-plating is what _Battery_
to employ, which will be the most simple, inexpensive, and effective
one. When the battery is only occasionally required for use we prefer
the Smee before any other. It is a small portable apparatus, and
consists of a high, but narrow, glass or stoneware jar, in the form of
a cylinder, capable of holding about two quarts; inside this jar is
fitted a thin plate of platinized silver fitted to a frame with two
zinc plates, one on each side of it, the zinc plates being held to
the frame by means of a binding screw. Strong copper wires are firmly
secured to these screws, which serve as the positive and negative
poles of the battery. Those parts of the plates which are not exposed
to the action of the acid solution may be advantageously coated with
sealing-wax varnish or melted paraffin wax, to protect them from the
destructive influences of the battery acid, and to prevent it from
creeping upwards, which destroys the connections. The jar is filled
with water acidulated with sulphuric acid, in the proportion of 1 of
acid to 20 of water; the frame containing the plates is then lowered
into the solution, and the battery is ready for use. In the above form
of battery for occasional use we have one simple in construction,
easy of management, of fair constancy, and when once prepared very
inexpensive, merely requiring a little free acid at times to keep
up the strength of the current. Two cells of this form of battery,
each holding two quarts of mixture, will be found sufficient for all
ordinary purposes. The zincs should be well amalgamated, and not touch
the bottom of the cells. The connections should be regularly examined,
and kept perfectly free from corrosion, which would stop the passage of
the current. For plating small delicate articles of jewellery one cell
of the above form will be found powerful enough for the purpose.
The battery that we prefer and have of late years employed, for
regular continuous working, is the Bunsen, consisting as before of a
cylindrical glass or stoneware jar of the same size and dimensions,
fitted with a well amalgamated _cylinder_ of zinc and a copper wire
secured to it; a porous cell is placed in the centre, and a bar or rod
of carbon is put into this cell with a copper wire also secured to it.
The porous cell is filled with a mixture of equal parts of nitric and
sulphuric acids, or sulphuric acid alone; we prefer the latter, as it
does not give off such fumes as does the other acid; a little of the
more powerful acid, however, is sometimes required to be added in order
to increase the action, as with this acid alone it sometimes becomes
slow. The outer cell is filled with a mixture of 1 part of sulphuric
acid to 20 parts of water, and the connections being in proper order
the battery is then ready for use. In action this form of battery is
regular and continuous, it lasts a long time upon one charge, and is
therefore inexpensive in use; if the two cells are coupled for power or
intensity, an unusual quantity of work may be got through in a given
time. This cell is admirably suited to the work of the manufacturing
silversmith, and to those who prefer doing their own plating.
The amalgamation of the zinc is effected as follows:--The cylinders are
best treated by putting some mercury into a coarse flannel bag, dipped
repeatedly into muriatic acid and applied to the surface of the zinc,
both inside and out; and when they present the bright characteristic
appearance of mercury they are sufficiently operated upon, and may be
rinsed and set aside to drain. The zinc plates may be advantageously
amalgamated by placing some mercury in a shallow dish with a little
muriatic or sulphuric acid, a hare's foot or a piece of cloth tied to
the end of a stick is then dipped into the mercury and acid, and rubbed
over the plates until they are sufficiently protected with mercury,
when they should be rinsed in clean water and set aside to drain. If
possible the process of amalgamation should always be conducted in
the open air, as the fumes which are given off, if breathed, are
highly injurious. The best possible way to amalgamate rods of zinc is
by pouring mercury into the melted metal just before casting it into
rods, in the proportion of 1-1/2 oz. of mercury to the pound of zinc.
This makes the rods exceedingly brittle, and they should therefore be
handled with care. The mercury should not be added to the zinc when the
latter is at too high a temperature, and the best manner of testing
this is by the application of a piece of paper to the molten metal,
when if it takes fire, the temperature is still too high; it should be
allowed to cool until the paper refuses to ignite, then and not till
then is the proper time for the addition of the mercury.
The copper conducting wires and binding screws must be cleaned when
they become much corroded; if not they add resistance to the current,
and it will become considerably diminished, or cease altogether. The
cleaning may be effected by simply annealing and then plunging them
while still hot into dilute sulphuric acid pickle, or dipping them into
nitric acid for about an instant.
The zincs should be taken from the battery liquids when not required
for use; and the porous cells should be removed every night and their
contents poured into a large jug kept for the purpose. The porous
cells should be placed in clean water to prevent the salts of the
battery liquid from crystallizing in the pores, which would crack and
spoil them for future use; the carbons should also be placed in water;
and when required for use again these arrangements should be reversed,
when the battery will work as well as ever.
The solution for electro-plating articles of jewellery is the next part
of the subject we have to consider, of which there are many, containing
various proportions of the metal employed in silver depositing. The
following is one of the best we have employed: take pure silver and
dissolve it in a mixture of nitric acid and water:--
Fine silver 5 dwts.
Nitric acid 4 drms.
Water 2 drms.
The silver should be put into a small Florence flask, so as to allow
the mixture of acid and water to cover it thoroughly; this mixture
on being added to the metal soon promotes a chemical action, and the
silver becomes gradually dissolved. If the acid employed has been
weak, it will necessitate a further addition of it to complete the
dissolution of the silver, or the removal of the flask to some other
and warmer place, such as a sand-bath, but care should be taken not
to apply too much heat. As the chemical action proceeds, red fumes
are formed in the flask; and the action should be allowed to go on
until these cease to rise, when the silver should by that time have
become dissolved. The mixture then consists of a solution of nitrate
of silver, and should be carefully poured into a suitable porcelain
or Wedgwood capsule; this is then heated upon a sand-bath until a
scum or pellicle appears upon the surface, when it should at once be
transferred from the sand-bath to a suitable place for cooling. During
the last operation the mixture begins to form itself into crystals,
and the liquid which appears reluctant to crystallize should be poured
away from those already formed, into another capsule, and again heated
until it has sufficiently evaporated to crystallize. When the whole
of the liquor has finally undergone this process, the crystals of
nitrate of silver must be removed to another vessel, and about one
pint of cold water added, the whole being then well stirred until they
have become thoroughly dissolved. A solution of cyanide of potassium
is next prepared in water, in the proportion of about one ounce of
cyanide to the pint of water; some of this solution is then added to
the one containing the nitrate of silver. It must, however, be added
very cautiously, for precipitation soon takes place, and if too much
be used, the precipitate becomes again dissolved. For this reason it
is advisable to take a little of the solution from the vessel, in
a wine-glass or test tube, and to add a few drops of the prepared
solution of cyanide, in order to ascertain its exact state. If the
application of this solution produces no effect upon the nitrate of
silver, the operation of precipitation is complete.
The liquid above the sediment should next be carefully poured away to
avoid any waste of silver; when this is done fresh water should be
added, well stirred with the sediment, and allowed to settle; it is
then again poured off, and the process repeated until the precipitate
has become thoroughly washed. Now add sufficient cyanide of potassium
to dissolve the precipitate and a little more, and make up two quarts
of solution with fresh clean water. It is better to filter the solution
before using it.
The solution may be made by means of the battery, and, if preferred,
the above mode of chemically preparing it may be dispensed with. The
following is the most simple method by the battery process:--Dissolve
in two quarts of water about half an ounce, and no more, of best black
cyanide; this should be done in an oval, or still better, oblong
stoneware vessel, placed in an iron one of the same shape containing
water. The stone jar should not be allowed to touch the bottom or
sides of the iron one, a space being left for holding the water. When
the cyanide has become dissolved, fill a porous cell with some of the
solution, place this cell in the other vessel containing the cyanide;
the solution should be about the same height in both vessels. Now
put a piece of sheet copper, secured to the end of the wire issuing
from the zinc of the battery, into the porous cell, and place in the
larger vessel containing the cyanide solution about one ounce of sheet
silver, properly secured to the wire issuing from the carbon of the
battery. In a short time the solution in the larger vessel will have
acquired the right proportion of silver (5 dwts. to the two quarts) for
use; when this has been effected, the porous cell should be removed
and its contents thrown away. These solutions are both worked hot, at
a temperature of not exceeding 120° Fahr. with the battery we have
described.
The solutions are heated by means of gas-jets, and the articles are
plated by being suspended to the wire proceeding from the zinc of the
battery. To the wire proceeding from the carbon is to be attached the
piece of sheet silver which dissolves and keeps up the strength of
the solution. The piece of silver or anode being lowered into the
solution, upon the immersion of the work, an almost instantaneous
deposit of fine silver takes place, the thickness of which depends
entirely upon the period of immersion.
When a solution begins to plate of an inferior kind through the
acquisition of organic matter, it will be better to abandon it
altogether and make a new one, rather than to waste valuable time in
repeated attempts at improvement, which seldom can be effected in
solutions that have been employed for all kinds of work. The silver
may be recovered from such solutions by means of the battery, by
precipitation, and by evaporation; the first process, however, we
have not always found successful, the solution in some cases refusing
to give up its silver to the action of the battery. It is put into
operation as follows:--The anode which supplies the solution with
silver is replaced by one of platinum, on which the cyanide solution
has no action whatever; a piece of clean sheet copper should be hung
upon the zinc wire of the battery, and the battery kept in action until
the whole of the silver held in the solution has become deposited upon
it; at which stage it may be removed, and the exhausted solution thrown
into the waste water tub. The piece of copper containing the silver
may be used again in the place of the silver anode until it has become
dissolved, or it may be removed by any other means, if preferred. In
the event of the above plan failing, the process of precipitation or
evaporation should be resorted to. If the former one be adopted, the
solution should be poured into a large open vessel, and considerably
diluted with water; sulphuric acid should then be carefully poured in,
a little at a time, until it produces no effervescence. The sulphuric
acid precipitates the silver, and the fumes which it creates are highly
deleterious to health, therefore the process ought to be performed in
the open air, and not in ill-ventilated workshops. When the sulphuric
acid produces no effect upon the solution, it should be allowed to
stand for a while for the precipitate to subside, when the water
above (which should be clear) may be drawn off, the precipitate well
washed, to free it from the acid, dried, and fused in a crucible with
a little potash or soda. If the latter plan be adopted, the solution
may be placed in a cast-iron kettle or saucepan, and then heated upon
a gas-jet or stove, until evaporation takes place, after which the
sediment should be removed and fused in a crucible, as before.
[Illustration: Fig. 40. Scratch-brush Lathe.]
The finishing of silver work requires some little knowledge and
skill to perform it properly; and we think that a few observations
bearing upon it will be of service to those for whom this manual is
written. After either of the processes of whitening or plating, the
work has to be scratched, unless required to be left a _dead_ white,
then this process does not take place; the scratching removes from
the surface the dull white colour produced by the above processes,
and effects a characteristic bright and uniform colour to the work
of the silversmith. Scratching is done at the lathe (Fig. 40) by the
application of a very fine brass-wire brush of circular form running
upon the spindle; a solution of weak ale runs from a barrel with a
tap to it, placed upon the framework of the lathe so as to enable the
beer running from it to fall upon the brush during the whole time of
its rotary action, and this assists the brush the more easily to glide
over the surface of the work submitted to it. A large quantity of
silversmith's work receives no other treatment than this, after the
whitening processes have taken place. Silver chains are burnished by
means of a polished steel jack chain, and the application of a little
soft soap and hot water, or otherwise scratch-brushed. The beautiful
frosted surfaces to be seen upon silver lockets, and other work of a
similar nature, are all produced by means of the scratch-brush.
Burnishing is another mode of finishing silver work. It produces a
polished surface, which reflects like a mirror, and gives the greatest
lustre: it removes marks left by the polishing mixtures, and produces
a darker surface than the other modes of finishing. The tools employed
for this process are extremely variable, and well adapted to the
different kinds of work to which they are applied; they are of two
kinds, one being formed of hard stone, and the other of polished
hardened steel; they vary with regard to shape, some being straight
with rounded points, or with curved and blunted edges, others with
large rounded surfaces, &c. Stone burnishers are made of blood-stone,
which is mounted in a wooden handle with a brass ferrule, which firmly
secures the stone to it, in which state it is used. Steel burnishers
are likewise fixed in wooden handles, which enable them to be firmly
grasped by the operator. Throughout the whole process of burnishing,
the tool should be repeatedly moistened with a solution of soap and
water; which causes it to glide more easily over the surface of
the work, prevents it from becoming too much heated, and generally
facilitates its action. In consequence of the great friction which
the burnishing tool undergoes, it soon loses its bite, when it slips
over the work as if it were greasy; its effectiveness must therefore
be restored from time to time by rubbing it upon the leather which the
workman has beside him for the purpose. It generally consists of a
piece of buff leather, impregnated with a little crocus. In very small
articles only steel burnishers are used, as they are finer in make, and
by their greater variety of form, are exceedingly well adapted to all
kinds of work; in this class of work, if any soap-suds should adhere to
the article they may be removed by the application of a little tissue
paper. Large pieces of work are rubbed with a piece of old linen, or
washed in a warm solution of soap and water, rinsed, and dried in
boxwood sawdust, which finally completes the process.
Silver work may be oxidized by any of the following processes:--
I.
Sal-ammoniac 2 parts.
Sulphate of Copper 2 "
Saltpetre 1 part.
Reduce the above ingredients to a fine powder, and dissolve it in a
little acetic acid. If the article is to be entirely oxidized, it may
be dipped for a short time into the boiling mixture; if only in parts,
it may be applied with a camel-hair pencil, the article and the mixture
both being warmed before using.
II.
Platinum 1 part.
Hydrochloric acid 2 parts.
Nitric acid 1 part.
Dissolve the platinum in the mixture of acid, evaporate to
crystallization, and when cold, dissolve again in a little sulphuric
ether. Apply the mixture with a camel-hair pencil to the parts required
to be blackened.
III.
Saltpetre 2 parts.
Common Salt 1 part.
Spirits of Salts 1 "
Reduce the salts to powder, and place it in a black-lead crucible along
with the acid, boil up, and then dip the articles into the mixture
for a short time, or otherwise apply it to the parts required to be
oxidized.
These mixtures will give the various tints of oxidation to silver work
if properly treated; but if other tints be desired, the following
chemical substances may be employed according to taste:--For
slate-coloured surface, dip the articles into a boiling solution of
sulphuret of potassium. Strong hydrosulphate of ammonia produces a
dark tint of oxidation, and if diluted with much water a light tint is
produced. Nitric acid produces a light surface. The fumes of sulphur
produce a beautiful blue-coloured surface. This operation should be
conducted in a closed box, and all parts not to be blackened should be
coated with a suitable resist varnish. After any of these processes the
articles may either be scratched, or otherwise burnished.
CHAPTER XI.
Imitation Silver Alloys.
The undermentioned white alloys have their various uses in the
industrial and mechanical arts, some being employed as common silver,
whilst others are manufactured as near as possible in imitation of it,
and used as a substitute, for many purposes. In melting the alloys
in which nickel and several other compounds enter into combination,
unless very great care be exercised, it is a difficult matter to
maintain the true and definite proportion of each metal of which the
alloy proper is composed, owing to the loss of the more fusible metals
by volatilization, if allowed to remain too long in the furnace. The
best method of preparing the compound for the crucible, is to mix
the copper and nickel together. The latter is produced from the pure
oxide of nickel; therefore it is taken in this form and placed in the
crucible with the copper at the commencement of the operation. When
these ingredients are well melted, and incorporated by stirring, add
the zinc or other fusible metal required to make up the compound,
previously heating it thoroughly over the mouth of the _crucible_, to
prevent the chilling of the already molten metal which it contains.
When silver forms a component part in any of these alloys it should
be added at the beginning of the process along with those of a high
degree of fusibility, and reduced under the protection of a suitable
flux; charcoal being the best for the purpose. This flux also tends to
preserve the fusible metals, upon their addition to the melted compound
in the pot, from too suddenly flying away in the shape of fumes. The
best zinc of commerce should be employed in these alloys, which is sold
under the name of spelter.
Common silver alloy alloy--
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 0 17 0
Nickel 0 13 0
-------------
2 10 0
=============
Another--
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 1 0 0
Nickel 0 15 0
-------------
2 15 0
=============
Common silver alloy--
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 1 3 0
Nickel 0 17 0
-------------
3 0 0
=============
Another--
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 1 6 0
Nickel 0 19 0
-------------
3 5 0
=============
Another--
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 1 9 0
Nickel 1 1 0
-------------
3 10 0
=============
Another--
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 1 12 0
Nickel 1 3 0
-------------
3 15 0
=============
Common silver alloy--
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 1 15 0
Nickel 1 5 0
-------------
4 0 0
=============
Another--
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 2 2 12
Nickel 1 7 12
-------------
4 10 0
=============
Another--
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 3 10 0
Nickel 1 10 0
-------------
5 0 0
=============
Another--
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 0 16 0
Nickel 0 10 12
Spelter 0 3 12
--------------
2 10 0
==============
Common silver alloy--
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 0 19 0
Nickel 0 12 0
Spelter 0 4 0
------------
2 15 0
============
Another--
oz. dwts. grs.
Fine silver 1 0 0
Shot copper 1 2 0
Nickel 0 15 0
Spelter 0 3 0
------------
3 0 0
============
Chinese silver--
oz. dwts. grs.
Shot copper 1 0 0
Spelter 0 6 0
Nickel 0 4 0
Cobalt 0 3 18
Silver 0 0 18
------------
1 14 12
============
Imitation silver--
oz. dwts. grs.
Shot copper 1 0 0
Nickel 0 6 12
Spelter 0 4 18
------------
1 11 6
============
Imitation silver--
oz. dwts. grs.
Shot copper 1 0 0
Spelter 0 12 0
Nickel 0 8 0
-----------
2 0 0
===========
Another--
oz. dwts. grs.
Shot copper 1 0 0
Spelter 0 8 0
Nickel 0 4 0
-----------
1 12 0
===========
Another--
oz. dwts. grs.
Shot copper 1 0 0
Spelter 0 10 0
Nickel 0 10 0
-----------
2 0 0
===========
Another--
oz. dwts. grs.
Shot copper 1 0 0
Nickel 0 8 8
Spelter 0 6 16
-----------
1 15 0
===========
White alloy--
oz. dwts. grs.
Shot copper 1 0 0
Tin 0 10 6
Brass 0 2 12
Arsenic 0 0 18
-------------
1 13 12
=============
Clark's patent alloy--
oz. dwts. grs.
Shot copper 1 0 0
Nickel 0 3 18
Spelter 0 1 22
Tin 0 0 12
Cobalt 0 0 12
-------------
1 6 16
=============
White alloy--
oz. dwts. grs.
Shot copper 1 0 0
Tin 0 10 0
Arsenic 0 1 0
-------------
1 11 0
=============
Alloy with platinum--
oz. dwts. grs.
Fine silver 1 0 0
Platinum 0 5 0
-------------
1 5 0
=============
Alloy with palladium--
oz. dwts. grs.
Fine silver 1 0 0
Palladium 0 5 0
-------------
1 5 0
=============
The platinum and palladium of which the last two alloys are composed,
although very difficult to use in combination with any other metal,
readily unite in any proportions with silver; and it has been found
that such alloys are not so easily tarnished as the ordinary ones, or
even as fine silver itself. These various alloys serve to effect the
several purposes for which they are employed in manufactures; wires
prepared from any of them will supply the place of silver, as brooch
tongs, stems for pins, catches and joints, &c. for articles of common
quality and cheap workmanship. They are also employed for preparing the
ground for "electro-plate," for which they are very serviceable. When,
however, these alloys are employed by the regular silversmith, care
should be taken not to get the scraps of metal in any way mixed with
those of the better material, otherwise difficulties will soon begin to
present themselves, which will materially interfere with the regular
and proper working of the best silver alloys; and in fact, with all
qualities that have originally been prepared free from nickel. Those
prepared from nickel are much more infusible than those made without
it; consequently, if a piece of the nickel alloy, either by accident
or design, gets intermixed with the other quality, in a subsequent
melting, it will be found to float upon the surface of the molten
metal for some considerable time, and thus retard the process. Alloys
prepared in imitation of silver are harder and much more difficult to
work than those of the true metal; therefore it can easily be imagined
what alteration the latter undergo upon the addition of some of the
former compounds. The hardness and toughness which these alloys possess
admirably adapt them for such purposes as we have described.
CHAPTER XII.
Economical Processes.
In all silversmiths' establishments, the economical or waste-saving
processes, as they are termed, require special and careful attention,
so that the actual working loss, or that portion of it which is
entirely irrecoverable by the manufacturer, may be reduced to the
lowest possible degree. It may not be known to the general reader, or
to the beginner in the precious metal trades, that there always takes
place in the working up of the metal a loss of material, a portion of
which the manufacturer is unable to recover, however cautious may be
the means employed for that purpose. In the best regulated workshops,
this loss will amount at the lowest estimate to about 2-1/2 per cent.
of the whole quantity worked up in the establishment. If the actual
loss can be reduced to within the above limit it is considered very
low, and highly satisfactory. Taking into consideration the loss
that is occasioned in precious metal working, and from calculations
that we have made from experience, we have long since arrived at the
conclusion, that it cannot possibly be estimated under 10 per cent.
of the total work daily performed; and this opinion is based upon
experiments, the _raw_ material being weighed before the process of
melting and after the articles were completed, a fair calculation
of course being made for unfinished work. This was including every
description of manufacture; in some branches of the trade the working
loss is not quite so great, but then there are others in which it is
exceedingly heavy, so that the estimated loss in the jewellery trades
cannot be safely put at a lower percentage than we have quoted.
It will thus be seen that the _real_ loss, such as manufacturers are
unable to recover by the means already known to them, amounts to
one-fourth part of the total working loss of the establishment. This
is easily accounted for: in the first place, a little takes place in
the melting of the various alloys, the re-melting of scrap metal,
the reduction of lemel, &c.; then there are the sundry manipulations
of working; the passage of the metal through various acids, and the
processes of finishing, each of which detaches small particles of
metal, too small to be visible to the naked eye, but all of which go
to form a portion of the loss which the manufacturer never recovers.
The unrecovered metal may be judiciously proportioned as follows:--A
portion of it works itself into the wood-work of the flooring of the
shops, lathes, boards, and other parts of workshop appliances; then
there is the refiner's profit--as purchases of the sweep, polishings,
and other refuse of precious metal workers. Instances can be recorded
in which shrewd business-men have actually taken up the floors of their
workshops and recovered a vast quantity of metal which was supposed
to be lost for ever; and instances are well remembered in which
two jewellers, upon removing into more extensive premises, availed
themselves of the opportunity, not only of removing the boards which
formed the flooring of the premises they were about to leave, but also
those of the tenants they were about to succeed. In one case, metal of
the value of £80 was recovered, and in the other it reached the large
amount of £150. The two jewellers referred to, of course, were too
un-English to refund the proceeds to the late tenants, who, when they
became aware of it, if ever they did, would be, no doubt, wiser if
sadder men.
To prevent the precious metal from finding its way into such places
as these, it is advisable to have the floors well protected with sheet
zinc or iron, in which case not the least particle could be lost in
this manner. The extra cost of laying the floors would soon be amply
repaid, by an extra quantity of the working loss being recovered; and
if other equally effective precautions were adopted in the waste-saving
processes by precious metal workers, the _real_ loss, which they cannot
avoid suffering, might even yet be reduced to the lowest possible
point. Iron or zinc covered floors may be protected from wear, by
laying over the surface small square grates of perforated iron, and
these, being removable, may be readily taken up at stated periods, for
sweeping the refuse from the floors; once a month will be found often
enough to do this. The gratings should, however, be swept over lightly
every day in order to remove the dust and particles of metal that may
accumulate upon the surface into the perforations, and also for the
removal of waste paper and other rubbish, continually accumulating in
workshops.
Floors containing no such waste-saving precautions, are commonly swept
over once, and sometimes twice each day, the refuse arising therefrom
being carefully passed through a very fine sieve, all extraneous matter
removed, and the residue remaining in the sieve being well sorted for
the detection of all the precious metal visible to the naked eye. The
whole refuse matter is then thoroughly burned in a muffle provided
specially for the purpose, and finally reduced to a fine powder in a
cast-iron mortar. When it has reached this stage of the process, it is
quite ready for the particular kind of treatment it next receives at
the hands of the refiner. Grinding by large stone rollers is now fast
superseding this mode of pulverising jewellers' waste and refuse. When
the latter plan is adopted, the refuse should be swept from the floors
every morning, carefully looked through, and then transferred to a
barrel (having the top removed, which may be used as a lid), where it
can be well kept together, and hidden from view until the time arrives
for its further treatment.
The waste which accumulates in the processes of polishing, lapping,
&c., is greater than that already referred to, consequently, it
cannot be too carefully looked after, in every stage, where a large
manufacturing trade is being carried on in various branches. It is
advisable in the practice of true economy, for the polishing, lapping,
and scratching boxes to be repeatedly cleaned out, and the contents
removed out of the temptation of every one, by being placed in a box,
well lined with either sheet lead or zinc, which ensures the perfect
safety of the material placed therein from all irregularities in the
workshop. This kind of waste on being prepared for sale is again placed
in a very strong wrought-iron box, made of a suitable size to fit the
muffle, and having a thick close lid to it. After the work of the day
has been completed, the fire in the furnace or muffle is made up,
the dampers are closed, and then the iron box containing the refuse
is at once passed in and allowed to remain there till morning, when
every particle of matter will have become thoroughly burned; a slight
pulverization after this process readily reduces it to a fine powder;
further operations then cease, and the product is in all probability in
a fine state of division, and fit for the subsequent operations of the
refiner and assayer, whose special business it is to attend to these
arrangements of precious metal workers.
The next process we have to consider is one which includes the
whole of the liquid substances variously employed in silver-working
establishments, such as the pickling solutions, washing-out waters,
whitening mixtures, and waste or spent solutions of every kind. The
whitening solutions or mixtures, when in use, should be kept apart
from the ordinary cleansing liquids, as after they have been in use for
a time, they become saturated with copper taken off the work during the
whitening processes; if the solution is then set aside for some time
the copper eventually crystallizes out from the liquor, which may be
poured into the waste-water tub, and the remaining crystals of sulphate
of copper, for such it then is, may be removed and preserved.
In small establishments one large tub, to form the receptacle for
all spent or used-up liquids, will be found sufficient; but in large
places several will be required. In the former case the water is only
drawn off at the beginning of every fresh week, which allows plenty
of time for the precipitation of the silver without any disturbance
taking place in the mixture between the close of one week and the
commencement of another; whereas in large concerns it requires to
be drawn off continually unless other vessels are provided for its
reception during a long period. Attempts have been made to recover the
silver from these solutions by simply filtering the liquid through a
coarse piece of felt or flannel; or by providing a false bottom in
the tub or other vessel containing the waste waters, arranged in the
following manner:--A tolerably large tub would be employed, being about
one-fourth filled with coarse deal sawdust, next would be placed the
false bottom perforated with numerous small holes, and upon this would
be firmly secured a piece of felt, so as to exactly fill up the space
in that part of the tub, which then serves to act as the filterer of
all solutions poured in above. The liquid after passing through the
piece of felt proceeds through the perforations in the false bottom
into the sawdust beneath, where it is allowed to run away by means
of a small hole or tap at the bottom. But the use of either of these
processes, if adopted on a large scale, where the waste products
amounted to some hundreds per annum, would be wretchedly bad economy
and tend to a serious loss of valuable metal; the boiling sulphuric
acid, used in cleansing the work and for other purposes, has the power
of dissolving minute particles of silver as well as those of the baser
metal which always enters into the composition used in the production
of the work of the silversmith; therefore, that portion of the metal
which has become dissolved and entered into the chemical state,
requires to be brought back to its original form before it can be saved
by such means as those just described. To illustrate this more clearly,
we will take the process of gold-colouring. If workmen were to notice
the rinsing waters employed in this process, subsequently allowing the
vessels containing the rinsing to stand for a very short time, upon
pouring away the surplus water, a white curdy precipitate will at once
be observed at the bottom. This is the silver removed from the surface
of the gold alloy, which has been precipitated by the muriatic acid
and the common salt employed in the colouring mixture, into the form
of _chloride of silver_. Now in this proceeding there is no gold to be
seen in any of the vessels, but it is a well-known fact that a portion
has been removed during the process from the surface of the gold
articles. Where is it? Why, it has become dissolved, and is therefore
held invisible in the solution, in consequence of the colouring mixture
forming the well-known solvent for gold, _aqua-regia_. This is exactly
the case with a portion of silver in the silversmith's solutions; small
particles are continually being dissolved by the mixtures employed,
and are thus held in solution past the power of filtering, unless
some chemical ingredient be added to it, which acts as a re-agent
upon the metal sought to be recovered. From what we have seen in the
colour water, which always contains a little silver, it is evident
that both muriatic acid and common salt will do this work for us. We
prefer common salt, on account of its cheapness, besides being easily
procurable.
The best mode of treatment for the silversmith's waste waters, after
being collected together by pouring into the receptacle specially
provided for that purpose, is to prepare a saline solution for the
precipitation of the silver. This may be made by mixing together common
salt and tepid water, in the following proportions:--
Common salt 3 oz.
Tepid water 1 pt.
The water need only be sufficiently warm to dissolve the salt, and
the proportions given do not require to be strictly adhered to; in
fact any quantity, if properly mixed, will do to effect the purpose
required, and we merely give these as a guide for the process. In small
establishments where only one tub is employed, the above proportion of
saline solution may be added (every Saturday after the completion of
the day's work) to the waste-water; the whole should then be stirred
slowly in a circular direction, and allowed to settle until Monday
morning, when all the surplus water may be drawn off and poured away.
In larger establishments the accumulation of waste-water is greater,
therefore several collecting vessels should be employed, and the
mixture for precipitation may be added to them at other times than
those stated, if required, and in accordance with workshop regulations.
The sediment produced in the collecting vessels after the supernatant
water has all been drawn off, may be removed, dried by heat in a strong
iron pan, and subsequently sold to the refiner.
CHAPTER XIII.
Licences and Duties.
Manufacturing silversmiths, and all persons trading in silver wares of
more than five pennyweights each, are compelled to take out a licence;
articles under that weight being exempt. The licence has to be taken
out annually, and costs £2 6_s._ for manufacturing or trading in
articles under thirty ounces in weight, and £5 15_s._ for articles of
thirty ounces and upwards. It should be taken out on the 6th day of
July in each year at the Excise Office. This Act of the Legislature
was passed in the year 1803, 43 George III. c. 69, and is not the
only one which refers to the subject we are now considering. There
are other conditions besides the compulsory _Plate Licence_, as it is
called, to which manufacturing silversmiths are subject, such as the
supervision of the assay offices, in the case of certain descriptions
of goods; and the payment of duty on all such goods. At the present
time all hall-marked silver articles have to pay a duty of 1_s._ 6_d._
per ounce, calculated not on their gross weight, but on five-sixths of
the weight, the other sixth being allowed for waste in finishing the
articles, as they are sent to the Hall in a half-finished state. The
duty is paid at the Assay Office at the time the goods are sent to be
marked. Some dissatisfaction just now exists in a portion of the trade
with regard to the above duty, as it is considered excessive, besides
having a tendency to discourage the manufacture of silver wares; be
this as it may with respect to a certain description of goods, on the
bulk of the trade it can have no injurious effect whatever. The duty
is paid only on manufactured _plate_ and such other articles as are
requested to be hall-marked; besides which the trade in this particular
department of manufacture has never been very extensive, being confined
to a few firms of eminence only.
Before going into the general details of this question, it will be as
well, perhaps, if we give a short history of the imposts that have
existed in the silver trade for some time back. The first impost that
we can find recorded took the shape of a _duty_, and was levied as far
back as the year 1720, by 6 George I. c. 11, which placed a tax of
6_d._ per ounce on all silver plate manufactured in Great Britain,
which, should be assayed or marked. The officers of the Excise were to
collect the tax, but the great difficulty of ascertaining the number of
ounces worked up, which the provisions of the Act did not clearly set
forth, soon rendered it ineffectual, and it was consequently repealed
by the statute 31 George II. c. 32, and a licence then substituted had
to be taken out by manufacturers and dealers in plate. The licence
at this period amounted to forty shillings, and had to be renewed
annually. In 1759, 32 George II. c. 14, it was increased to £5 per
annum, for every person trading in silver wares of thirty ounces and
upwards; wares in one piece not exceeding five pennyweights in weight
being exempted.
The next change that took place was in the year 1784, 24 George III. c.
53, when a duty was again imposed of 6_d._ per ounce on silver plate.
It was also enacted that the assay masters should stamp the work with
the additional mark of the "King's head," as well as the others already
ordered by the various Acts of the Legislature. The mark of the King's
head represented that of the reigning sovereign, and showed that the
duty had been paid on the work. The present mark, therefore, is the
Queen's head.
By an Act passed in the year 1797, 37 George III. c. 90, the duty on
silver ware was increased to one shilling per ounce, but the Act which
subjected silver wares to a duty of 6_d._ per ounce (24 George III. c.
53) has not been repealed, and is therefore in existence to this very
day; by its provisions, however, the duty has been increased from time
to time, until it has reached the amount at which it now stands.
The present annual licences of £2 6_s._ and £5 15_s._ respectively,
were enacted in the year 1803 by an Act of 43 George III. c. 69, and
by these regulations every person making or trading in silver wares,
or otherwise dealing in the raw material, is compelled to take out an
annual licence, or render himself liable to a penalty of £50.
Another Act was passed in reference to the duty on silver goods in the
year following, 1804, 44 George III. c. 98, whereby it was increased
to 1_s._ 3_d._ per ounce. And in the year 1815, 55 George III. c. 185,
the Act was further extended to 1_s._ 6_d._ per oz. calculated in the
manner we have described at the beginning of this chapter. To sum up,
therefore, the silver _duties_ in their several forms, bearing upon the
trade at the present time, we find them as follows:--
Manufacturers of silver wares under 5 dwts. in weights.--_Exempted
from all duties._
Vendors and dealers in silver wares under 5 dwts. in
weight.--_Exempted from all duties._
Manufacturers of silver wares under 30 oz. in weight.--_A plate
licence of £2 6s. annually._
Vendors and dealers in silver wares under 30 oz. in weight.--_A
plate licence of £2 6s. annually._
Manufacturers of silver wares of more than 30 oz. in weight.--_A
plate licence of £5 15s. annually._
Vendors and dealers in silver wares of more than 30 oz. in
weight.--_A plate licence of £5 15s. annually._
Bullion dealers, refiners, and assayers.--_A plate licence of
£5 15s. annually._
Manufacturers of plate.--_A duty of 1s. 6d. per ounce._
Hall-marked goods.--_A duty of 1s. 6d. per ounce._
Manufactured plate includes silver wares, such as spoons, forks,
snuff-boxes, tea-sets, &c., and other articles used by the rich, and
upon which the duty is compulsory; the duty on hall-marked goods,
refers to all articles--with the exception of watch-cases, which are
free--marked at the request of intended purchasers, which then pay duty
on the manufacture of them. It will be observed from these remarks,
that the silver trade generally is not at all affected by the _duty
tax_; the wares manufactured by the trade at large not coming directly
under the compulsory provisions of the law bearing upon this subject.
It has been said that the silver trade ministers to luxury, and no
doubt that portion of it which manufactures costly articles of plate
for the wealthy does so; but we fail to see exactly, that the same
remark applies to that vast and increasing commercial industry which
has sprung up of late years, and which bids fair to become one of the
staple trades of the country. The duty-bearing articles are generally
purchased by the classes of society who can well afford to pay the
little extra which the duty imposes, and as the tax affects only that
section of the silver trade which manufactures the article of luxury,
it is not at all likely that the general trade would be increased
by its entire removal. The duty, no doubt to most persons, may seem
excessive, when calculated upon the percentage system; such for
instance, as a tax of 20 per cent. upon spoons and forks; or one of 15
per cent. upon chains; or of 12-1/2 per cent. upon tea-sets, &c.; this
appears unjustly oppressive, and undoubtedly affects the _silver-plate_
manufacturer more vitally than any one else.
To the ordinary silversmith this question of duty is not likely to be
of much importance; the agitation therefore commenced against it, may
be expected to confine itself to those persons more directly affected,
and whose interests would be advanced by its abolition.
The question of licences is one of far greater importance to the trade
generally than that of duties, every manufacturer and dealer being
compelled to procure a licence before he can carry on his business. If
more direct action were taken in regard to this particular question,
we believe that the whole trade would enter into it; for it resolves
itself into this:--Why should the silversmith or goldsmith pay for a
licence for the purpose of manufacturing and dealing, any more than the
coppersmith, or the manufacturer of electro-plate, both of whom escape
scot-free? We believe this to be an unjust tax, and that it ought not
to be levied upon one particular trade any more than another. We have
also distinctions made in the general class of silversmiths: we have
those who may trade without any licence at all; those who may trade
with a 46_s._ licence; and those who may trade with 115_s._ licence,
that is, those who work or sell under 5 dwts., those who work or sell
under 30 oz., and those who work or sell at any weight. Now this way of
arranging the matter is very unsatisfactory to the trade generally; and
any one of the first two traders to whom we have referred, is liable at
any moment to be summoned before a criminal court for an infringement
of the law, if he should happen to sell an article slightly over the
weight for which he is duly licensed. At the present time a raid is
being made upon the goldsmiths with reference to this particular
question, and a number have already been summoned for infringing their
licences in this manner. However, there appears to be some doubt with
respect to the Act of Parliament bearing upon the subject, as in most
of the cases the defendants have gained a verdict, the line of defence
on their behalf being, that the clause of the act which bore upon the
cases referred to, meant the weight in fine metal, _i.e._ "pure gold,"
of which the article was composed, and not that of the gross weight of
the article sold. It was urged by those engaged in the various cases
on the side of the defendants, that, for a 46_s._ licence, the vendor
could sell an article in which the gold did not exceed two ounces,
without any regard to the quality and weight made by alloy, and on this
plea the magistrates granted them a verdict. In the higher courts we
believe such verdicts would be reversed, for we firmly believe that
the framers of the act meant no such thing, however defective may have
been the legality of the points raised. The clause of the act to which
we have alluded is No. 5, and runs as follows:--"All articles sold,
or offered for sale, or taken in pawn, or delivered out of pawn, and
alleged to be composed wholly, or in part, of gold or silver, are for
the purposes of the above act to be deemed to be composed of gold or
silver respectively; and if upon the hearing of any information for
any offence against this act, any question shall arise touching the
_quantity_ of gold or silver contained _in any article_, the _proof of
such quantity_ shall be upon the defendant." The Excise authorities
argue that this clause means that the absolute or gross weight of
an article sold as gold must not exceed two ounces, and one sold as
silver must not exceed thirty ounces, gross weight. If this view of the
meaning of the act be eventually taken, and we believe it will, it will
certainly operate to a greater extent against makers and vendors of
gold articles than it will against silversmiths.
That part of the _clause_ referring to the quantity of gold or silver
contained in a given article, we believe has reference to articles
containing jewels, &c., in their construction, which renders it
exceedingly difficult to get at their exact weight, when the work is
finally completed with these jewels properly affixed upon it, and
not to the amount of fine material any article may contain by assay.
The last part of the clause we have marked in italics, "proof of
such quantity shall be upon the defendant," fully bears out these
observations, because he is supposed to know the gross weight of any
special article before the addition to it of any jewels.
We have been led to make these few remarks, in order to point out
the gross anomalies which exist in the trade with respect to these
licences, and to show the necessity of a reform taking place in a
trade singled out from all the others, and made to pay a tax for the
privilege of being allowed to make, or sell, articles in which gold or
silver forms a component part. Therefore, if any action is to be taken
in the matter, it must not be confined (if it is to be successful) to
one particular branch of this important trade, but all must unite, and
every influence should be brought to bear upon it in as forcible a
manner as possible. The electro-plate manufacturer, and the dealer in
_his_ wares, ought in all common fairness to the trade, to be put upon
the same footing as the silversmith, if this licence is to be still
continued. In electro-plating establishments, thousands of ounces of
silver are being annually used on the surface of such wares as are
manufactured there; and if such decisions as those lately given at the
Thames and other police courts, with reference to the Act of Parliament
on the subject of gold and silver wares are upheld, we fail to see
how the manufacturers of silver-plated articles, who are continually
making and selling them, containing as they do, more silver than the
general public would suppose, are to escape much longer these new
interpretations of the Act of Parliament, and avoid being called upon
to take out a licence in the same manner as the silversmiths. This is
a tax in which the holder gets no direct return, and is levied in an
unfair manner by the establishment of various grades of silversmiths,
so that it gives a just cause for grievance. If the tax is to be upheld
at all, why not make it equal by the establishment of one uniform rate
for all trades alike?
CHAPTER XIV.
Useful Information for the Trade.
Silversmith's Alloy.
Copper, 1 oz.; nickel, 3 dwts. 12 grs; bismuth, 6 grs.; zinc, 2 dwts.
12 grs.; soft iron, 12 grs.; tin, 12 grs. This compound is said to
form a fusible and malleable metal, that can be easily worked by the
silversmith; it is also said to resist oxidation through atmospheric
influences.
Silver Wares.
Never scratch-brush silver ware with a solution of soap and water;
neither should it be washed with the solution if it can be avoided, as
it gives it the colour of pewter; better to scratch in weak ale, or if
plain, rub it with a piece of wash-leather and prepared chalk.
Cleaning Plate.
Carbonate of ammonia, 1 oz.; water, 4 oz.; Paris white, 16 oz.; well
mix the ingredients together, and apply to the surface of the plate by
means of a piece of soft leather or sponge.
Imitation Silver.
Fine silver, 6 dwts.; nickel, 6 dwts.; copper, 8 dwts. This alloy will
cost about 1_s._ 9_d._ per ounce.
Another Recipe.
Fine silver, 5 dwts.; nickel, 6 dwts.; copper, 9 dwts. Cost about 1_s._
6_d._ per ounce.
Removing Gold from Silver Articles.
Silver articles which have been gilt, may be brought back to their
original colour, by simply covering them with a thick solution of
borax, and then well annealing them. After this process if the articles
are boiled for a short time in one of the whitening mixtures and
scratched, they will present a beautiful white and uniform surface.
Oxidizing Silver.
A beautiful deep black colour, possessing great lustre, may be given
to finished silver work by boiling it in the following preparation
for some time:--Bromine, 5 grs.; bromide of potassium, 5 dwts.;
water, 10 oz. The boiling should be effected in a stoneware pipkin,
and generally from two to five minutes will suffice for the purpose.
The work is finished after the proper colour has been attained, by
well rubbing with a soft piece of wash-leather and a little best
jeweller's rouge. It is better to make the work as bright as possible
before submitting it to this mixture; for this reason it is preferable
to thoroughly buff all plain surfaces on a piece of felt by the
application of the lathe, as by that means a characteristic brightness
is imparted.
Dipping Mixture.
Brass or metal goods may be cleaned and their oxides removed by
dipping into the undermentioned liquid for a few seconds only:--Oil of
vitriol, five parts; water, five parts; nitric acid, two and a half
parts; spirits of salts, two drachms. Well mix the several ingredients
together, and immerse the work in the solution cold. The mixture
improves after a quantity of work has been dipped into it.
Silver Powder for Copper.
Chloride of silver, two parts; cream-of-tartar, two parts; alum, one
part. Mix with water to the consistence of a paste, and apply with a
soft leather or sponge; when sufficiently whitened, well polish.
Powder for Silver.
Chloride of silver, 1 oz.; sal ammoniac, 2 oz.; sandiver, 2 oz.; white
vitriol, 2 oz.; bichloride of mercury, 5 dwts. Make into a paste with
water and rub the articles over with it; then expose them to a good
heat upon a clear fire, in order to run the silver and evaporate the
mercury, after which process dip in very weak sulphuric acid to clean.
To Protect the Polish of Metals.
Melt one part by weight of best wax paraffin and when sufficiently
cooled, add three parts of petroleum. Well mix together, and apply to
the polished articles by means of a soft brush. The protecting film is
required to be only very thin, therefore too much should not be put on.
Silver Stripping Mixture.
Sulphuric acid, six parts; nitric acid, one part. Take a large
black-lead crucible or pipkin, and heat the mixture in it; when this is
done, put in the work required to be stripped, occasionally withdrawing
it to ascertain the progress made. The large proportion of sulphuric
acid allows of the dissolution of the silver, and does not sensibly
corrode or interfere with copper, or any of its alloys, if kept quite
free from water; therefore be careful not to introduce wet articles
into the mixture. After finally withdrawing the work, it should be well
rinsed, annealed, and then boiled out.
Stripping Silver.
Put some strong oil of vitriol in a similar vessel to those above
described, apply heat, and during the process add a few crystals of
saltpetre. When the solution has become hot enough the work should
be immersed in it, and be moved about or agitated until the silver
is dissolved from the surface. The articles should not be allowed to
remain too long in the solution, and if it does not remove the silver
quickly, more saltpetre should be added from time to time until the
desired end be attained.
Soft Solder.
Pure tin, two parts; lead, one part. Melt and well incorporate
together; when this is done pour into strips for use.
Soldering Fluid.
Muriatic acid (spirits of salts), three parts; metallic zinc, one
part; or as much as the acid will take up. When dissolved and all
effervescence ceases, allow it to settle, then decant the clear
solution from the sediment at the bottom of the vessel in which it
has been made, and it is ready for use. If a small quantity of water
be added to the mixture at this stage, say one-sixth, it will answer
quite as well for some purposes. For soldering iron and steel, a very
small portion of sal ammoniac is of great advantage to the mixture for
promoting toughness.
_Dissolving fine silver._--Nitric acid, two parts; water, one part.
_Dissolving silver alloys._--Nitric acid, one part; water, two
parts.
_Dissolving copper._--Nitric acid, one part; water, four parts.
_Dissolving soft solder._--Perchloride of iron, one part; water,
four parts.
_Dissolving silver solder._--Nitric acid one part; water four parts.
_Dissolving sealing-wax._--Place for a time in a solution of
spirits of wine.
Resist Varnish.
Dissolve resin, or copal, in essence of turpentine, or boiled linseed
oil; to give it different shades of colour, add red lead, chrome
yellow, or Prussian blue.
Plate Powder.
Whitening, two parts, white oxide of tin, one part, calcined hartshorn,
one part. Reduce to a powder and well mix together; apply as usual.
Electro-plating Soft Solder.
Take nitric acid, 1 oz.; water, 2 oz.; copper about 1 oz. in small
flat pieces; when the copper has all dissolved and effervescence has
ceased, the solution is ready for use. To apply it, take up a few
drops by means of a camel-hair pencil and apply it to the desired
part, then touch it with a bright piece of steel, and there will be
instantaneously a film of copper deposited. If the copper has not
spread all over the desired part, the process should be repeated, when
deposition in the plating bath will take place with perfect success.
Another Recipe.
Take sulphate of copper (that which accumulates in the whitening
mixture), one ounce; water, six ounces. Reduce the sulphate of copper
to a fine powder and dissolve it in the water. Treat according to the
directions given in the previous one. A good mixture for effecting the
same result may be made by dissolving verdigris in vinegar.
Testing Silver Wares.
Take nitric acid, six ounces; water, two ounces; bichromate of potash,
one ounce. Reduce the salt of potash to a powder and well mix it
with the acid and water. The solution is used cold, and should be
placed in a stoppered glass bottle, the stopper having a long dropper
extending into the mixture, which acts as the agent for conveying the
liquid from the bottle to the article to be tested. The surface of
the article should be perfectly clean, and to make certain what kind
of metallic substance you are testing, it is advisable to rub a file
over some obscure part of the surface and to apply the liquid to that
part. The test liquid should be used, by means of the glass stopper,
to the filed part, and immediately removed by a sponge damped with
cold water. If the article consists of pure silver, there will appear
a clean blood-red mark, which is less deep and lively in proportion to
the quality of the metal. Upon platinum the test liquid has no action
whatever; on German silver at first a brown mark appears, but this is
removed by the sponge and cold water; on Britannia metal a black mark
is produced; and on all the various metals an entirely different result
takes place to that on silver; therefore the test is a simple one,
and may be advantageously employed for the detection of any fraud in
relation to the precious metal.
Another Test.
Water, 2 oz.; sulphuric acid, 2 drs.; chromate of potash, 4 dwts. This
mixture is applied in the same way as before and produces a purple
colour of various depths, according to the quality of the silver. No
other metallic element exhibits the same colour with this preparation.
Perchloride of Iron.
Take spirits of salts, 8 oz.; crocus powder (jeweller's polishing
material), 1 oz.; well mix them together and keep in solution. In
preparing the mixture for the dissolution of soft solder, &c., take 1
oz. of it, and add to it 4 ozs. of boiling water.
Aluminium Alloy.
Copper, 18 dwts; aluminium, 2 dwts.
New Alloy.
Zinc, 19 dwts; soft iron, 1 dwt. This alloy is said by the inventor to
be remarkable for its whiteness and tenacity.
Removing Gold from Silver Wares.
Sometimes the process of annealing and boiling-out fails to effect the
removal of the gold from articles which have been thickly gilt, in
which case the work should be submitted to the action of the following
chemical preparation:--Sulphuric acid, 6 ozs.; muriatic acid, 1 oz.;
nitric acid, 1/2 oz. This mixture should be heated in a black-lead
crucible or earthen vessel, and the work immersed until the dissolution
of the gold takes place, carefully watching it during the progress of
the operation. The gold may also be removed by using a strong solution
of oil of vitriol, to which has been added a fair proportion of common
salt.
Silver Plating Fluid.
Nitrate of silver, 1 oz.; cyanide of potassium, 2 ozs.; water, 12 ozs.
Put the cyanide and the nitrate of silver into the water; shake them
well together until they become thoroughly dissolved, then let the
mixture stand till it becomes thoroughly clear. It is then ready for
use. If preferred, a little prepared chalk may be used as an additional
ingredient.
Plate-cleaning Powder.
Take of the finest rouge, and prepared chalk, equal parts, well mix and
use dry by means of soft leather.
Solder for Aluminium.
Spelter, 18 dwts.; aluminium, 1 dwt. 6 grs.; copper, 18 grs. To be
employed for soldering the _pure_ white metal, and not the so-called
aluminum bronze, that being commonly soldered with bath-metal solder.
CHAPTER XV.
Foreign Silver Standards--Pre-War.
Table showing the various standards of the silver work manufactured in
the principal countries previous to the European War, 1914-1918:--
+------------+------------------+------------+---------------+
| | | Thousandth | |
| Countries. | Silver per oz. | parts. | Remarks. |
+------------+------------------+------------+---------------+
| | oz. dwts. grs. | | |
| France | 0 18 23 | 948-1000 | Old Standard. |
| " | 0 19 0 | 950-1000 | 1st " |
| " | 0 18 0 | 900-1000 | Coinage. |
| " | 0 16 0 | 800-1000 | 2nd Standard. |
| Germany | 0 19 0 | 950-1000 | 1st " |
| " | 0 18 0 | 900-1000 | 2nd " |
| " | 0 16 0 | 800-1000 | 3rd " |
| " | 0 15 0 | 750-1000 | 4th " |
| Austria | 0 19 0 | 950-1000 | 1st " |
| " | 0 18 0 | 900-1000 | 2nd " |
| " | 0 16 0 | 800-1000 | 3rd " |
| " | 0 15 0 | 750-1000 | 4th " |
| Geneva | 0 19 0 | 950-1000 | 1st " |
| " | 0 17 12 | 875-1000 | 2nd " |
| " | 0 16 0 | 800-1000 | 3rd " |
| Holland | 0 17 12 | 875-1000 | Old Standard. |
| " | 0 18 16 | 933-1000 | 1st " |
| " | 0 16 16 | 833-1000 | 2nd " |
| Belgium | 0 19 0 | 950-1000 | 1st " |
| " | 0 18 0 | 900-1000 | 2nd " |
| " | 0 16 0 | 800-1000 | 3rd " |
| Spain | 0 14 18 | 738-1000 | Lowest " |
| Portugal | 0 16 21 | 844-1000 | One only. |
| Neuchatel | 0 16 0 | 800-1000 | One only. |
| Russia | 0 16 19 | 840-1000 | 1st Standard. |
| " | 0 15 0 | 750-1000 | 2nd " |
| Italy | 0 19 0 | 950-1000 | 1st " |
| " | 0 18 0 | 900-1000 | 2nd " |
| " | 0 16 0 | 800-1000 | 3rd " |
| China | 0 19 14-1/2 | 980-1000 | About. |
| Norway | 0 16 19 | 840-1000 | One only. |
| Sweden | 0 16 19 | 840-1000 | " |
| Denmark | 0 16 19 | 840-1000 | " |
+------------+------------------+------------+---------------+
In France, all articles manufactured as silver are subject to
_Government control_ and pay duty, but this is very slight compared
with the English duty, amounting only to one _franc_ per _hectogramme_,
which is equal to about threepence per ounce. This is exclusive of the
charge for testing and marking; the state of the articles sent for this
purpose with regard to the state of manufacture is, moreover, very
different from the custom in this country. Here they are sent in their
rough or half-manufactured state, and this seems better suited to the
particular processes through which they have to pass; whereas in France
they may be tested and marked in their whole or finished state; and,
if thought requisite, this operation may be performed while the goods
are on their way to their final destination, by calling at the Control
Office for that purpose.
The Continental silversmiths, especially the French workmen, exhibit
much ingenuity, original thought, and refined taste, in the execution
of their work; and the natural capacity for design which they possess
enables them to produce articles of a very high order and artistic
character. The construction of some of their productions is exceedingly
ornamental and decorative, and in some instances this is even carried
to excess, as may be seen from some very elaborate articles which they
manufacture.
To them belongs the credit of being producers of the most artistic and
best decorative work in the whole world. They set the _fashions_ and
work them out with a will to be only found in a people so enthusiastic
as the French. Their jewellery is very elegant, light, and showy;
some of which is prepared so thin as regards material, that it has to
be supported underneath by a wax composition, which, however, gives
increased strength to all articles so manipulated. With regard to
articles of _vertu_, the French workmen certainly far excel those
of any other country: they are more original, and bring into play
greater ingenuity in the various processes which they employ in their
manufactures. Still with all this ingenuity and skill, their works of
art in this department are not durable, being very _tinselfied_; in
wear their shape and form soon undergo a change, and eventually they
soon get destroyed. In this branch of art the French workman might
learn something to his advantage from the English style of work, which
is the most durable of any nation in the world. French silver plate and
jewellery of the best manufacture partake of the first standard; all
other kinds are of the lowest standard.
In Germany all silver manufactures are placed under _Imperative_
control, and lower standards than those given in the table, under
their respective heads, cannot be worked. The German style is similar
to that of the French, but the former manufacture an unusually large
quantity of filigree articles, very light in construction, tasteful,
and cheap; and the possession of these advantages enables them to
export to England and other countries their wares at a cheap rate.
They are commonly sold by weight, and not so much per article; in many
cases the charge does not exceed 12_s._ 6_d._ per ounce. In filigree
work the Germans cannot equal the taste and variety displayed in Indian
workmanship. In India the natives have definite designs, but the
Germans are too fond of a variety of colours in their wares, which do
not always harmonize with their particular kind of work.
In Austria silver manufactures are commonly ornamented by enamel,
niello, &c., which gives them a very pleasing appearance. They are
usually light and showy, and something after the style of French work.
The laws affecting the Austrian silver workers are the same as those of
Germany.
The English style of work is strong and solid; and is undoubtedly
superior to that of all Continental manufacturers as regards
substantial workmanship, careful manipulation, and durability. It is,
moreover, capable of a higher finish, and possesses more evenness of
surface, together with a combination of strength, that admirably suits
it for articles and utensils for daily use, and which causes it to be
preferred before that of any other nation; and while France, Germany,
and other countries may exhibit greater ingenuity, to England belongs
the credit of producing the best _finished_ and the most _durable_ work
of any nation in the world.
INDEX.
Acids, vegetable, 10
Action of acids on copper, 44
of silver under heat, 8
Acts of the Legislature, 189
on licences, 186
clause on, 193, 194
Advantages of scorification, 20
Air in furnace, 33
Alkalies, caustic, 10
Allowed, remedy in fineness, 72
Alloy, 41
Clark's patent, 172
commonly used, 63
for cupel quantity, 35
for hall-marking, 62
for plate, 71
for silver-wares, 72
French, for coinage, 69
French, for plate, 69
French, for silver-ware, 69
German, for coinage, 71
instructions in preparing, 70
new, 205
Nos. 1 to 8, 64-67
of the highest quality, 62
silver dissolving, 202
standard, 61
white, 172
Alloy, with copper, 68
with palladium, 173
with platinum, 172
Alloys of common silver, 167-170
characteristics of, 173, 174
imitation, 166-173
imitation, uses of, 173
of nickel, 46
of silver, 42
of tin with gold, 49
of tin with silver, 49
silversmith's, 40, 197
Aluminium alloy, 205
solder, 206
Amalgam, 41
Amalgamation of zinc, 153
America, 11
American supply of silver, 12
Ancient method of assaying, 37
workers in tin, 48
Ancients, 6
Annealing silver, 109
Anthracite, 21
Art in soldering, 90
in the silver trade, 122
Articles, hand-made, 54
of silver common, 147
Art of soldering, 74
Arts, metals employed in, 41
Assay crucible, 16
charge for, 17
English system, 39
fluxes, 16
of silver ores, 16
scorification, 19
weighing of, 30
Assayer's muffle, 28
Assaying, borax, use of, in, 22
Dr. Lamborn on, 38
of silver ores, 16
Austrian style of work, 211
Battery, Bunsen's, 152
constant, 150
exciting mixture, 151
for plating, 150
solution, 151
Bean-shot copper, 44
Best crucibles, 95
Birmingham, 52
Black cyanide, 157
Blowpipes, 89
Boiling-out mixture, 144
pan, 143
pickle, 93
Bone-ash, 32
cupel, 33
Borax, 22
sprinkle, 92
Breaking-down rollers, 112
Brightening, 29
British Isles, 11
Brown colour on silver goods, 146
Burning of lemel, 104
of polishings, 179, 180
Burnished silver work, 124
Burnishing silver work, 161, 162
Calculated alloys, various, 80
Calculating the qualities of silver, 64
Carbonate of soda, 16, 102
Casting-mould, 18
Cause of inferior work, 74
Caustic alkalies, 10
Cement for chasers, 121
Chain bracelets, 128
Chain solder, 85
Characteristics of imitation alloys, 173, 174
of metals, 41
Charcoal, 99
Charge and flux for crucible, 23
for assay, 17
for scorification assay, 20
Chief places for filigree, 53
of filigree manufacture, 8
uses of silver, 9
Chinese filigree, 56
silver, 170
Chloride of silver, 183
Christianity and tin, 48
Clark's alloy, 172
Cleaning plate, 198
powder for plate, 206
Coinage, 69
alloys for, 71
English, 61
French, 69
German, 71
Collecting-vessels, 184
Colour-improving, 149
Common articles of silver, 147
easy solder, 85
silver alloy, 167-173
silver solder, 84
solder, 85
solders, 81
Composition for solder, 81
Conducting-wires, 154
Connections for soldering, 77
Constant battery, 150
Continental cheap labour, 54
method of assaying, 22
silversmiths, 208
Copper, 42
action of acids on, 44
bean-shot, 44
characteristics of, 43
chemical name, 44
dissolving, 202
for alloying, 68
powder for, 199
protoxide of, 44
solder with, 76
Cost of silver alloys, 64, 67
of silver-rolling, 112
Cronstedt, 45
Crucible, dimensions, 16
for lemel, 106
mixture for, 104
pouring lemel from, 107
weighing metal for, 95
Crucible assay, 16
fluxes for, 16
process of, 19
Crucibles, 95
best to employ, 95
action with fluxes, 96
testing soundness, 97
Cupel, defects in, 33
mode of manufacture, 26
mould, 27
quantity of alloy for, 35
tongs, 28
withdrawal of silver, 34
Cupellation, 26
of silver ores, 31
purity of silver, 37
Cup-fusing, 19
Currents of air to furnace, 33
Cyanide solution, 156
black, 157
Defects in bone-ash cupel, 33
Density of nickel, 45
of silver, 7
of tin, 48
Dimensions of crucible, 16
Dipping-mixture, 199
Directions on melting, 94
in preparing solders, 88
Discoverer of electro-plating, 149
Dissolving silver, 202
copper, 202
impurities, 103
soft solder, 202
silver solder, 202
sealing-wax, 202
tin, 48
Dissolution of silver, 9
Dr. Lamborn, 38
Drawbacks to hall-marking, 63
Draw-bench, 114, 115
Drawing fine wire, 116
Draw-plate, 114
Draw-tongs, 115
Drossy solders, 88
Drum for wire-drawing, 115
Ductility of nickel, 45
of silver, 6
of tin, 49
of zinc, 48
East Indian silversmiths, 141
Easy solders, 79
for chains, 85
silver solder, 80
solder, 81
solder, for filigree work, 84
solder, common, 85
Economical processes, 175
Economy, 1
Education, technical, 2
Electro-plate, 46
Electro-plating, 147
discoverer of, 149
soft solder, 202
Elements, metallic, table of, 50
Employed metals, 41
Enamelling, 131
England, alloy commonly used, 63
English and foreign workmen, 2
coinage, 61
filigree workers, 91
silversmiths, 63
standard for silver, 60
style of work, 211
system of assay, 39
Enriching the surfaces of silver, 139
Exciting mixture for battery, 151
Experts, Government, 73
Filigree manufacture, 8
method of making, 57
of China and Japan, 56
of Norway and Sweden, 56
silver work, 127
wire, new, 59
work, 5, 40, 52
working, 56
Filed solders, 76
Flatting of twisted wire, 59
Flux and charge for crucible, 23
for soldering, 77
in pouring, 101
Fluxes for assay, 16
their action on crucibles, 96
employed in melting, 96
Foreign silver currency, 13
silver standards, 207, 8
workmen, 2
French alloy for silver ware, 69
alloy for coinage, 69
alloy for plate, 70
French duty, 208
standards, 69
style of work, 209
Fusibility of nickel, 45
of tin, 48
of silver solders, 80
Fusing-cup, 19
Galvanic ring, 129
German coinage, 71
standards, 72
style of work, 210
Gold alloyed with tin, 49
mode of soldering, 88
removing, from silver, 198, 205
Goods, silver, brown colour of, 146
Government experts, 73
Gravity, specific, of zinc, 47
Great Britain, 11
Guarantee mark, 73
Hall-marking, alloy for, 62
drawbacks, 63
Hand-made articles, 54
Hard silver solders, 79
solder, best, 81
Hardest silver solder, 78
silver solder, 79
Hardness of silver, 8
Hawk-sparrow, 119
Heating power of silver, 7
Hollow silver work, 131
Imitation silver alloys, 166, 173
alloys, characteristics of, 173
alloys, uses of, 173
silver, 166, 197
Improving colour of electro-plate, 149
Impurities, dissolving, 105
Indian filigree workers, 5
Indian filigree silversmiths, 141
mode of whitening, 142
Industrial arts, 41
Inferior plating solution, 159
Ingot-mould, 100
Instructions in preparing alloys, 68
Irregularities in rolling-mills, 110
Japanese filigree, 56
Jewellery trade, state of, 12
Law on silver wares, 73
Lead, 103
Legislature, Acts of, 186
Lemaille solder, 91
Lemel, 104
burning, 104
crucible, 106
melting, 104-106
pot for, 104
pouring from crucible, 107
Licence question, 191
Licences, 190
Litharge, 17
Loss, working, 175
real, 175
total working, 176
Making filigree, 56
Malleability of nickel, 45
of silver, 6
of tin, 49
of zinc, 48
Maltese filigree, 55
Manner of removing litharge, 35
Manufacture of cupels, 26
inferior, 73
of filigree, 53
of silver wares, 72
Mark, guarantee, 72
Marking, hall, 62
Marking, hall, drawbacks of, 63
Material, bad working, 98
Mechanical uses of silver, 52
Medium solders, 82
silver solder, 79
Melting, crucible for, 99
directions on, 94
fluxes employed, 96
imitation alloys, 166
points of metals, 51
solders, 86
tongs for, 100
Mercury, 15
Metal, fusible, 98
pure, 56
Metallic elements, table of, 50
Metals, 41
their characteristics, 41
Method of assaying, 22
for whitening, 139
of calculating qualities, 64
of preparing filigree, 59
Mills, rolling, 110
Kemp's, 111
Mine, richest, 12
Mining, 11
Mixing metals for melting, 97
Mixture, boiling-out, 144
dipping, 199
for washing-out, 138
stripping, 200
Mixtures for whitening, 147
for battery, 152
nitrate of silver, 148
Modes of melting lemel, 105
of preparing ring, 130
of whitening, Indian, 142
of whitening, our, 145
Molten metal, 99
lemel, 103
Mould-casting, 18
Mould cupel, 27
Mould ingot, 100
Muffle assayers, 28
Native silver, 11
Necessity for pure metal, 56
New alloy, 205
method for filigree, 59
Nickel, 45
Nitrate of silver, 8
of silver, mixture, 148
Nitre, 10
Norway filigree, 56
Old method of filigree, 57
Oldest method of whitening, 140
On the melting of silver, 94
working of silver, 108
Ores of silver, 9
Our mode of whitening, 145
Oxidizing silver work, 163
Palladium alloy, 173
Pallion solder, 89
Parliament, Acts of, 190
Perchloride of iron, 205
Physical properties of metals, 51
Plain solid work, 127
Plate, 4
alloy for, 70
cleaning powder, 206
electro, 46, 150
French, 70
manufacture, 190
powder, 202
Plating, battery for, 150
discoverer of, 149
electro, 150
fluid silver, 206
soft solder, 201
solution, 157
Plating solutions, recovery of silver, 160
Platinum alloy, 172
Plumbago, crucible for melting, 99
Polished silver, 7
Polishing, 135
lathe, 137
Polishings, burning of, 179
Pouring off lemel, 107
Powder for silver, 200
Precious metal, 1
Precipitation of silver, 183
Preparation for assay, 17
of bone-ash, 32
of plating solution, 155
of solders, 87
Present state of silver trade, 128
Press, 127
stamping, 132
Price of silver, 9
Principal alloys of silver, 42
metals, 51
Process, scorification, 18
advantages of, 20
details of, 23
of silver recovery, 180-183
Producing various shades, 165
Production of surface, 135
Protect polish of metals, 200
Protoxide of copper, 44
of zinc, 102
Pure silver, 3
Purity of silver, 37
Qualities used by silversmiths, 64
Quantity of alloy for cupel, 35
Quick-running solder, 85
Raised work, 120
Raising, 122
Recovery of silver from waste, 160
of silver from waste waters, 183, 185
Refining surface of silver, 146
Remarks on silver solders, 80
Remedy in fineness, 72
Removal of litharge, 35
Removing gold from silver, 198
gold from silver-wares, 205
Resist varnish, 202
Ring, galvanic, 129
preparing wire for, 130
Rollers, slitting, 112
breaking-down, 112
Rolling, silver, 108
mills, 110
silver, 112
wire, 113
Sal-ammoniac, 103
Saving waste, 177
Scientific name for tin, 49
Scorification process, 18
assay, 20
Scorifier, 19
special form, 19
Scrap silver, 102
Scratch-brushing, 161
brush lathe, 161
Scriptural testimony, 37, 38
Sealing-wax, dissolving, 202
Sediment, 185
Separation of silver, 21
Shades, 165
Shop floors, 177
Shot copper for alloying, 44
Silver a precious metal, 1
action under heat, 8
alloy, dissolving, 202
alloy for coinage, 72
alloy, standard, 61
alloyed with tin, 49
alloys, Chinese, 170
alloys, common, 167, 172
alloys, imitation, 167, 172
Silver alloys, No. 1, 64
No. 2, 64
No. 3, 65
No. 4, 65
No. 5, 66
No. 6, 66
No. 7, 67
No. 8, 67
American supply, 12
and aqua-regia, 8
and mercury, 15
annealing, 109
articles, 194
articles, common, 147
assay, 14
British, chief sources, 13
British yield, 11
burnishing, 162
characteristics of, 5
chief alloy of, 30
chloride, 183
commercial, 9
currency, 6
currency, foreign, 13
density of, 7
dissolution of, 9
dissolving, 202
ductility of, 6
easily tarnished, 129
European supplies, 12
filigree work, 125
for filigree work, 5
fusibility of, 7
goods, brown colour, 146
hardness of, 8
heating power of, 7
imitation, 198
known to the ancients, 6
law on, 73
lead and tin in, 103
malleability of, 6
mechanical uses of, 52
Silver, method of calculating, 63
mining, 11
native, 11
nitrate of, 8, 148
ores, 9
ores, assay of, 16
oxidizing, 163, 198
plating fluid, 206
polished, 7
powder, 199, 200
powder for copper, 199
precipitating, 183
principal alloys, 42
pure, 3
purity of, after cupellation, 37
recovery of, 160
recovery, 177, 178
rolling, 109
rolling, table of cost, 112
solders, 81
solder, dissolving, 202
solder, easy, 82
solder, hardest, 79
solder, medium, 82
solder, zinc in, 46
solders, fusibility of, 80
standards, foreign, 207
stripping mixture, 200
surface, improving, 139
tarnished, 7
test for, 6
trade, art in, 123
uses of, 9
various qualities, 52
ware, 69, 195
ware, French, 69
ware, German, 71
wares, alloys for, 72
wares, removing gold, 205
wares, testing, 203
weighing, 30
whitening of, 140
Silver work, burnished, 124
work, hollow, 131
yield of, 13
Silversmiths, 63
alloys, 40, 197
continental, 209
East Indian, 141
working, 2
Skittle-pot, 25
for lemel, 104
Slitting-rollers, 112
Snarling-tools, 122
Soda, carbonate of, 16, 102
Soft solder, 90, 202
dissolving, 202
plating, 202
Solder, composition for, 81, 98
best hard, 81
common, 83, 85
common easy, 86
dish, 89
easy, 79, 82, 86
filed, 76
for aluminium, 206
for chains, 85
for filigree, 84, 91
hard, 77
Lemaille, 91
medium, 76, 82
pallion, 88
quick running, 85
very common, 87
with arsenic, 86
with copper and silver, 76
with zinc, 76
Soldering, art of, 74, 90
alloy, dissolving, 202
connections, 77
mode of, 88
fluid, 201
flux, 77
Solders containing tin, 75
Solders, drossy, 88
for enamelling, 84
melting of, 83
preparations of, 87
remarks on, 80
tin in, 49
Solid plain work, 127
Solution for battery, 151
cyanide, 156
for plating, 157, 158
for precipitation, 184
inferior, 159
No. 1, 163
No. 2, 164
No. 3, 164
Soundness of crucibles, 97
Spain, 11
Sparrow-hawk, 119
Special soldering flux, 92
Specific gravity of zinc, 47
Spelter, 46
used by jewellers, 47
Spinning, 134, 135
Sprouting, 29
Stamped work, 126
Stamping-press, 132
Standard alloy for hall-marking, 62
alloys of the highest quality, 62
Standards, English, 60
French, 70
German, 71
State in which silver is found, 14
State of silver trade, 128
State of the jewellery trade, 12
Stone, Water-of-Ayr, 136
Strength of solution, 152
Stripping silver, 201
Style of work, Austrian, 211
English, 211
French, 209
Style of work, German, 210
Indian, 210
Surface, refining of silver, 145
Swedish filigree, 56
System of assaying, 39
Table of cost of silver-rolling, 112
of metallic elements, 50
of various duties, 90
Tarnishing of silver, 7
of zinc, 47
Tax or licence, 196
Technical education, 2
Test for pure silver, 6
Testing crucible, 97
silver wares, 203
Testimony, Scriptural, 37, 38
Test-ring, 31
Tin, 48
alloyed with gold, 49
alloyed with silver, 49
ancient workers, 48
and Christianity, 48
density of, 48
dissolving, 48
ductility of, 49
fusibility of, 48
in solders, 49, 76
malleability of, 49
scientific name, 50
tenacity of, 49
vapours, 49
Tongs, draw, 115
Tongs for melting, 100
Total working loss, 176
Trade, silver, state of, 128
useful information for, 197
Treatment, economical, 1
in furnace, 18
of waste, 179
Treatment of waste liquids, 180
Twisting wires, 58
Unjustly assessed tax, 195
Uses of silver, 9
borax, 22
for imitation alloys, 173
of lathe, 58
silver, mechanical, 52
Vapours of tin, 49
Various qualities of silver, 52
duties, table of, 190
metals, mixing, 95
Varnish, resist, 1
Wares, ornamental, 4
law on, 73
removing gold from, 205
silver alloy for, 72
silver, 197
testing purity, 203
Washing-out mixture, 138
Waste, saving, 178
liquids, treatment of, 180
treatment of, 181
waters, 182-185
water, precipitation in, 184
Water-of-Ayr stone, 139
Weighing of silver assay, 30
Whitening, old method, 140
Indian mode of, 142
our mode of, 145
powder, 147
Wire for filigree, 59
rolling, 112
drawer's drum, 115
drawer's punch, &c., 117
drawing, fine, 117
Wires, conducting, 154
Withdrawal from cupel, 34
Work, Austrian style, 211
burnishing, 162
English, style, 211
filigree, 5, 40, 125
French duty on, 208
French style, 209
German style, 210
hollow, 131
Indian style, 210
silver, burnishing, 124
solid, 127
stamped, 132
Workers, Indian, 5
Working filigree, 56
loss, 175
material, bad, 98
silversmiths, 2
total, 176
Workmen, English and Foreign, 2
Workmanship, process of, 55
Wrought work, 118
Yield of silver, 11, 13
Zinc, 46
a fusible metal, 98
amalgamation, 153
annealing, 47
ductility of, 48
gravity of, 47
in silver solder, 46, 76
malleability of, 48
on floors, 178
tarnishing of, 47
tenacity of, 48
PRINTED BY WILLIAM CLOWES AND SONS, LIMITED, LONDON AND BECCLES.
LOCKWOOD'S MANUALS
_Trade_
Clock Repairing Garrard Net 6/-
Watch Repairing Garrard " 6/-
Mechanical Dentistry Hunter " 6/-
Electro-Plating Watt " 5/-
House Painting Davidson " 7/6
Carpentry and Joinery Tredgold " 6/-
Gas-Fitting Briggs " 6/-
Bricks and Tiles Dobson " 7/6
Metal Plate Work Barrett " 3/6
_Technical_
Engineers' Screw Cutting Pull " 2/6
Engineering Measuring Tools Pull " 4/6
Slide Rule Hoare " 4/-
_Craft-Work_
Modern Fretcutting Makinson " 2/6
_Art-Work_
Illuminating Whithard " 6/-
_Educational_
Portuguese Dictionary Elwes " 8/6
_Business_
Foreign Commercial Correspondent Baker " 7/6
_Complete List on Application._
LONDON:
CROSBY LOCKWOOD & SON
Transcriber Note
The following changes were made:
p. 47 "Fahr." moved from after "6·8 and 7·2" => to after "773°"
p. 93 "week pickle" => "weak pickle"
p. 175 "regulated workships" => "regulated workshops"
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