Age & Authenticity: The materials and techniques of 18th and 19th century goldsmiths

Age & Authenticity The Materials and Techniques of 18th and 19th Century Goldsmiths

Jack Ogden National Association of Goldsmiths 1999

Age and Authenticity

© Jack Ogden 1999

Available from the National Association of Goldsmiths, 78a Luke Street, LONDON EC2A 4XG. UK.

Age & Authenticity The Materials and Techniques of 18th and 19th Century Goldsmiths

Jack Ogden National Association of Goldsmiths 1999

Forward This brief investigation into the materials and techniques of the 18th and 19th century British gold- and silversmiths is perhaps a natural progression from my work on ancient and medieval precious metals. The foundations lie in my involvement with the jewellery and silver industries over some 30 years, while the scientific research and development of analytical approaches largely derive from research carried out while running the Cambridge Centre for Precious Metal Research a trading name of Independent Art Research Ltd.

It is perhaps surprising that there is far more published on the technical aspects of ancient and medieval precious metals than on Renaissance and later. As noted in the introduction, "'It is strange that while most jewellers are aware of the various gemmological approaches that can be used to characterise gemstones … few art historians, jewellers, jewellery collectors or auctioneers seem to be aware of the various ways in which technical criteria can be used to aid the dating and authentication of antique precious metal jewellery."

This volume is an attempt to redress this situation and provide a preliminary look at a field that deserves far more research. As methods of analysis advance and become more accessible, it seems likely that the analysis of trace elements will become more and more common as a means of supporting opinions as to origin and authenticity. At the other end of the scale, even basic magnification equipment such as an inexpensive microscope or even 10x hand lens can reveal much with regards to technique and construction. Perhaps the overriding message is that scientific examination is now an integral part of art historical examination in general, and jewellery study in particular.

This brief publication would not have been possible without the help of numerous dealers, collectors, auctioneers, metallugists and museum curators who, over the years, provided me with objects to study and sample. Needless to say, this is not intended to be the final word on the subject and I can make no pretence at more than scratching the surface of the varied and fascinating documentary evidence that relates to the subject. Any suggestions as to possible dating criteria based on material composition and technique are simply suggestions and my opinions that will need to be confirmed (or not) by fuller research programmes in the future.

Jack Ogden

1999

Contents INTRODUCTION ................................................................ 1

1. TECHNOLOGY ................................................................... 3 A tale of two cities ............................................................... 4 The rolling mill ..................................................................... 5 The piercing saw................................................................. 6 Casting ............................................................................. 6

Lost wax casting ............................................................................ 8 Detecting castings .......................................................................... 8

Wire drawing ....................................................................... 9 Findings ............................................................................. 9 Die stamping ..................................................................... 10 Surface colouring .............................................................. 10

2. MATERIALS ..................................................................... 13 3. THE SUPPLY OF RAW MATERIALS............................... 15

Metal supplied by refiners and bullion dealers .................. 15 Coinage ........................................................................... 17 Scrap ........................................................................... 20

4. GOLD AND SILVER ......................................................... 23 Gold ........................................................................... 23 Silver ........................................................................... 25

5. OTHER METALS PRESENT IN THE ALLOYS, INCLUDING TRACE ELEMENTS .................................... 27 Arsenic ........................................................................... 28 Bismuth ........................................................................... 28 Cadmium........................................................................... 29 Gold as an impurity in silver .............................................. 30 Indium ........................................................................... 33 Iron ........................................................................... 33 Lead ........................................................................... 33 Manganese ....................................................................... 34 Nickel ........................................................................... 34 Platinum group metals ...................................................... 34 Tin ........................................................................... 36 Zinc ........................................................................... 37 Solder alloys ..................................................................... 40

6. THE FUTURE.................................................................... 43 REFERENCES........................................................................ 45

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Introduction Assessing the age and authenticity of antique or historic precious metal articles involves much more than just comparing their overall form and design with known parallels. It is also vital to look at the construction and constituents of jewellery. Nevertheless, it is strange that while most jewellers are aware of the various gemmological approaches that can be used to characterise gemstones and most silver collectors, appraisers and dealers are at least aware of the analytical techniques which can often provide the dating evidence of silver objects, few art historians, jewellers, jewellery collectors or auctioneers seem to be aware of the various ways in which technical criteria can be used to aid the dating and authentication of antique precious metal jewellery. In fact there is almost an inverse law working here. There is a far greater number of studies of Greek and Roman goldsmithing technology than of Renaissance, and while analyses of ancient gold and silver items run into hundreds of volumes and articles, those dealing with Georgian or Victorian can be counted almost on the fingers of one hand.

This is not the place to complain about the artificial divide between 'art history' and 'technology' that has blighted the study of fine arts for generations. However, we should be able to agree that we can longer justify disassociating materials and techniques from style and form if we wish to build a fuller picture of the past.

As what has just been said implies, there are two main 'technical' areas that can be investigated:

1. The techniques used to form and join the components of the objects.

2. The materials used to make and join these components.

These will be considered in turn.


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1. Technology The technology used to make the components of a piece of jewellery and to assemble them into a complete object has been used as an indicator of authenticity for some time. However, the goldsmith's craft is a very conservative one and most of the main 'marker' techniques use to characterise and thus authenticate jewellery relate to ancient rather than more recent times. For example, differences in technique between Roman and Renaissance times are far more recognisable and definable than changes between, say, the Renaissance and the late Eighteenth Century.

In ancient times, in the countries bordering the Mediterranean Sea, gold jewellery was primarily a sheet-metal industry.1 Jewellery components were cut and shaped from hammered-out sheet gold, the softness and malleability of which permitted the forming of intricate three-dimensional forms. These sheet components could be decorated with minute granules of gold made by fusing small specks of gold into spheres or with wires made by hammering and smoothing strips of gold or by twisting thin ribbons of gold. The components were joined by a variety of soldering techniques, or, in the case of larger components or where flexibility was required, by links or loops of wire.

There were some technological advances with time – such as the introduction of wire drawing in about AD 700 – but in essence the industry remained much the same right up to the time of the Industrial Revolution in the second half of the eighteenth century.2

In earlier times it had been usual for goldsmiths and jewellers to make their own tools, but the industrial processes for manufacturing and mass-producing steel equipment developed during the Industrial Revolution had major repercussions for the jewellery industry. Now, for example, the rolling mill and piercing saw were options in a typical jewellery workshop.

The Book of Useful Trades and Library of the Useful Arts of 1818 describes a jewellery workshop as including a draw bench, a 'flattening mill' for sheet and piercing saws.3 These three pieces of equipment are of relevance with regards to development chronology.

The nineteenth century also witnessed a growing rift between the traditional jewellery workshops producing hand-made jewellery and those more focussed on mass-production.

The traditional craft had always relied more on skill and experience than costly or complex equipment. Wallis writing in the 1870s sums this up:

'The tools and appliances necessary for a working jeweller to start in business on his own account are comparatively few, and a few pounds enables him to secure every requisite for carrying on the production of jewellery by hand. A peculiarly shaped work bench, a jet of gas, or the flame of a candle or lamp, some solder, and the inevitable blowpipe, with a vice, hammer, shears, files, punches, and drills, may be said to pretty nearly represent the plant. A few old coins, or for want of them some new ones, a few ounces of silver and zinc, and your working jeweller can commence his business.'4


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The mass-production developments in the jewellery industry in the second half of the nineteenth century, in the wake of a high-spend and burgeoning middle class, set the seal on a modern practical approach to jewellery manufacture that is still continuing. However, in the nineteenth century this did not necessarily involve a reduction in number of those required in the workforce. As an example, chain-making machinery was in use in Birmingham in the second half of the nineteenth century. In 1852 Charles Dickens had the following to say:

'Twenty years ago, the making of gold chains occupied a dozen or twenty people in Birmingham. Now, the establishment we are entering, alone, employs probably eight times that number. Formerly, a small master undertook the business in a little back shop: drew out his wire with his own hands; cut the devices himself; soldered the pieces himself; in short, worked under the disadvantage of great waste of time, of effort, and of gold. Into the same shop more and more machinery has been since introduced as it was gradually devised by clever hands. This machinery is made on the spot, and the whole is set to work by steam.'5

A tale of two cities The increasing production of mass-produced jewellery was changing the face of the industry and, to a large extent, the separation of the industry between handcraft and mass production characterised two different cities – London and Birmingham.

In the second half of the nineteenth century Cheapside in London represented the tradition of 'pure handicraft' while London's 'West End' produced high class and court jewellery. In Birmingham the trade depended far more on mechanical methods and hand labour was 'reduced to a minimum'. Indeed, as Wallis noted in 1878, most articles of jewellery made in Birmingham 'may be said to be flung together'.6

Dickens expressed the two city distinction in the following way:

First, however, we may as well mention, in confidence to our readers, that our feelings are now and then wounded by the injustice of the world to the Birmingham manufacturers. We observe with pain that the very virtues of Birmingham manufacture are made matters of reproach. Because the citizens have at their command extraordinary means of cheap production, and produce cheap goods accordingly, the world jumps to the conclusion, that the work must be deceptive and bad. Fine gentlemen and ladies give, in London shops, twice the price for Birmingham jewellery that they would pay, if no middlemen stood, filling their pockets uncommonly fast, between them and the manufacturer; and they admire the solid value and great beauty of the work; but as soon as they know where the articles were wrought, they undervalue them with the term "Brummagem."7

Even Wallis does admit that 'it must not be forgotten that there is now a large and constantly increasing demand for artistic hand-made jewellery, which is supplied by many firms in Birmingham as well as London.'8

What follows is not intended to be a full study of 18th and 19th century precious-metal working methods. It focuses briefly on a handful of processes that were affected by the Industrial Revolution or the growing technological advances of the 19th century, namely the use of the rolling or 'flattening' mill, the piercing saw, casting and die stamping. Wire drawing is also mentioned, not because there were

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significant changes during the 18th and 19th centuries, but because the history of the technique, particularly its roots, interests jewellery historians. The birth of the 'findings' industry is also mentioned, as is the surface treatment of gold. Although surface 'colouring' processes were of considerable antiquity and conservative in the extreme, their application in recent times relates to the types and purities of the gold alloys in use.

The rolling mill The rolling or 'flattening' mill was used to produce gold or silver sheet. A gold or silver ingot was passed between two smooth steel rollers, thereby making it thinner but of greater area. Adjustment would bring the rollers fractionally closer and the metal would be passed again between them; a process repeated until the metal had reached the required thickness. Small versions were worked by hand by a handle, much like a small, sturdy washing 'mangle', larger ones by steam, water or horse power. Such machinery was complex to produce. In particular the two rollers between which the gold or silver was passed had to be exceptionally regular and smooth.

The flattening mill is first attested in the fifteenth century and was quite possibly invented by Leonardo da Vinci. Initially the prime purpose appears to have been for producing controlled, and regular, thickness gold and silver for manufacturing coin blanks.

Rolling mills found some use in the European iron industry at least as early as the beginning of the 17th century and from this same period we find occasional references to the use of rolling mills for gold and silver.9 However, use in the precious metal industry was still mostly for use in the mints. For example a cast iron rolling mill was supplied to the London mint in 1690 and the early eighteenth century example in the Hermitage (Fig. 1) was presumably also for coining purposes.10

Rolling probably first came into prominence in the precious metal trades for the production of Old Sheffield Plate after 1742. In the second half of the 18th century we see a marked increase in the number of patents for metal rolling mills and increasing evidence for their use in the jewellery and related industries. A simple hand-rolling machine is shown in a jewellery context in the mid-eighteenth century Encyclopédie of Diderot.11

In 1763 Lewis explained the flattening mill process where gold was 'passed repeatedly between polished steel rollers' and informs us that this was a relatively recent innovation since hammers had been used previously.12 This is mirrored in the 1819 Cyclopedia of Arts, Sciences and Literature. Here Rees says that 'the business of the goldsmith formerly required much more labour than it does at present, for they were obliged to hammer the metal from the ingot to the thinness they wanted: but now there are invented flattening mills which reduce metal to the thinness that is required at a very small expense.'

The Book of Useful Trades in 1818 notes that the flattening mill 'cannot be dispensed with, where the business is considerable'.13 As can be imagined, considerable use was rare in a traditional jewellery workshop and it was more usual for goldsmiths to obtain their sheet (generally rolled from their own metal) from specialists. Even in the finer London hand-work establishment in the late 1870s: 'The working jeweller, taking into consideration the exigencie of his materials,

Fig. 1 Rolling mill, dated 1710 and probably originally for producing sheet for coinage blanks. Hermitage, St. Petersburg


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proceeds to cut and shape the thin plates of gold, which in most cases is ready rolled to a suitable thickness.'14 At this time the various branches of the London jewellery trade included 4 masters and 40 workmen operating 'flatting mills'.15 As Gee also noted, rolling 'is a distinct branch of the trade, and is carried on in separate premises established by certain firms for the purpose.'16

The evidence that a rolling mill has been used for the production of the sheet metal used to form an object is a good indication of a manufacturing date within the last couple of centuries or so. A clear visible indication of the adoption of the technology can be seen with British antique silver where styles best suited to manufacture from pre-rolled silver sheet, such as conical and octagonal coffee pots, started to supersede the laboriously hand-raised, more globular forms. This is a direct relationship between technology and style and just one of the instances in jewellery and silverware history where stylistic advances are due as much to new technology as to lightning bolts of artistic inspiration. On a more microscopic scale, the parallel surface striations typical of rolled sheet metal (in an area untouched by polishing or other operations) are a useful dating tool.

Today, of course, jewellers usually tend to obtain gold sheet from their metal suppliers in the thicknesses required, although some have small rollers for their own use.

The piercing saw The piercing saw is well known to anyone who has worked at the bench, as is the very short life expectancy of the thin steel blades. No wonder that the piercing saw was rare if not unknown in precious metal workshops much before the mid eighteenth century when the mass-production of fine saw blades became a technical and economic possibility.

The earliest piercing saw in a jewellery workshop context I am aware of is illustrated in Diderot's encyclopædia of the mid eighteenth century (Fig. 2). I would be surprised if fine piercing saws were in general use much before this date and they might well have been rare before the nineteenth century.

The employment of the piercing saw is generally easily spotted by its characteristic square-ended cut (Fig. 3). Such indications are a very helpful dating tool with antique jewellery and silver. For example, traces of the use of such a saw can be seen on some 19th – early 20th century fakes of Renaissance jewellery.

As with the rolling mill, the introduction of the piercing saw is an advance that can be linked to stylistic changes. The introduction of open-backed settings for diamond jewellery around 1800 is traditionally linked to changes in diamond cutting styles. However, a moment's reflection tells us that it wouldn't have been a simple matter to produce elaborate open-backed settings without access to a piercing saw.

Casting Cast gold jewellery is so ubiquitous today — for many categories of gold jewellery the vast majority is now cast — that its general employment in the past is often taken for granted.

Casting was used in historical times, but seldom for items of gold jewellery. Silver candlesticks, for example, or silver fittings, could be cast, but gold jewellery seldom

Fig 2. Piercing saw as used in a jewellers workshop. Diderot's Encyclopedia, 1751 – 57.

Fig. 3. Square-ended piercing saw cut on the handle of a purported 17th century silver bowl.

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was.

Of course, with the exception of the most primitive work, all gold at some time or another during the production process is melted and ‘cast’. For example Hiorns talks of gold cast into bars for converting to strip and wires and cast gold plates used in the early stages of locket production.17 However, casting was rarely used in the Ancient Mediterranean world and was scarce even in the Medieval and later European gold jewellery-making traditions for producing near-finished forms.18

George Gee's Goldsmith's Handbook demonstrates that this was also true until very recent times. The first edition published in the 1870s makes no mention of casting for the jeweller and even in the 1936 edition the only mention of casting is relegated to the appendix and in the context of mould production.

There were several reasons for avoiding the casting for gold, including:

• Relatively high purity gold does not cast well. It flows poorly in the mould, shrinks, and so produces poor-definition castings. In the words of an 18th century observer 'gold is less fit for receiving sharp and perfect figures, when cast into mould, than silver, copper, lead or tin, which do not shrink so much'.19 It is relevant that the regions that employed casting for gold in the past – including Prehistoric Northern Europe and Precolumbian South America – typically used lower carat gold alloys often with copper as primary additive. Such alloys are far better for castings.20

• It was usual for the customer to supply the goldsmith with the gold with which to work. However, there was no way to produce a mould to exactly utilise a pre-determined weight of gold and thus wastage was inevitable.21

• Castings have surface roughness, ‘casting fins’ and ‘sprues’ to remove, meaning extra labour and weight loss

Thus casting was unsatisfactory and really only became a serious option after the acceptance of lower carat gold (in 1854 in the UK); the use of different alloying metals (including zinc after the mid 19th century); and the changing practice of the jeweller producing a stock rather than just making up his customers’ gold to order.

There was some use of casting for one-off jewellery items in the 19th and early 20th centuries – such as for some of the ubiquitous copies (and fakes) of ‘Renaissance’ jewels (thus contrasting with the fabricated gold 'skeletons' of the genuine examples). The two main processes used were cuttlefish, in smaller workshops, and sand casting for factory production. Centrifugal casting, that provided less porous castings, though used in dentistry from around 1908, was seemingly only adopted in the jewellery industry in the 1930s. Casting was seldom used for day-to-day or mass-produced jewellery until post World War II.

Silver objects or, more often, components of silver objects such as mounts or handles, were more frequently cast, but there were still problems such as shrinkage and thus loss of sharpness and detail. Silver shrinks by about 5% on cooling from a melt. Indeed such shrinkage is significant enough for size to be a determinative factor in identifying cast 'hallmarks'.

Major variations in the composition of cast (sterling) and wrought (sub-sterling) components noted with some eighteenth English silver items examined by me might indicate that local silversmiths were able to 'buy in' ready made cast components.


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The need to ‘clean-up’ cast silverware is shown by an order of the Standing Committee of Court of Assistants to the Worshipful Company of Goldsmiths in 1760: 'no cast work shall be assayed or tried unless the same shall have been well boiled or filed, so that the barb be taken clean off from every piece'.22

Lost wax casting

The best type of casting for fine jewellery and jewellery components is called lost wax casting. In this process a wax model is made of the desired form. This wax model with an attached stalk-like wax sprue is coated in layer upon layer of fine clay termed the ‘investment. The investment is fired and in the process the wax melts out. The jeweller is thus left with a lump of solid clay with an internal cavity that is an exact ‘negative’ of the original wax model. Molten gold is poured in through the hole left by the ‘sprue’ and, once cooled and solidified, the investment is broken off to reveal a gold replica of the original wax — except for the sprue that has to be cut off.

An obvious limitation here is that each wax model and investment can only be used once. An advance came when it was realised that the wax models could be mass-produced by making a two-part rubber mould of the original model. Then a whole series of identical wax models could be made, fixed together into ‘casting trees’ by joining the ends of their sprues to a central ‘trunk’ and then casting the whole tree in one operation (Fig. 4).

The production of castings in this way revolutionised the jewellery industry. However, it is salutary to note that this revolution only occurred post-World War II. The use of rubber moulds was patented in the 1930s. Even in 1945 Selwyn commented that lost wax comments itself for artistic subjects, but 'Its one disadvantage, and it certainly limits its use in commercial work, is that at conclusion of the process the cire (wax) is indeed perdue (lost). Only one object can thus be made, unless a further wax model is made for every fresh casting.’23

Detecting castings

Castings made by this lost wax/rubber mould technology (which unsurprisingly include a wide range of ‘Victorian’ rings) can usually be identified by the remnant casting fins or ‘seams’ caused by minuscule misalignment of the two parts of the silicon rubber mould during wax model production. These seam-like lines are often visible as a slight undulating ridge, for example around the inside of a ring shank (Fig. 5).

Lost wax can also result in minute spherical globules on the surface which are 'beads' – often looking very much like stray granulation – are frequently seen on cast jewellery including fakes of antique and ancient pieces.24 In theory, of course, such globules could occur on ancient or antique items cast by the lost wax technique, but if they occur in conjunction with irregular casting ‘fins’ they are certain proof of the use of a silicon rubber mould in the lost wax process – a post WW2 development.

Another casting characteristic — and thus a method of recognition — is porosity. Porosity is actually caused by minute gas bubbles that appear as tiny pin-pricks or open bubbles in the final casting. Polishing can obliterate surface porosity, but it can often still be observed, particularly on the backs of items and inside ring shanks. Porosity is not an indication of one type of casting rather than another, but it is an

Fig. 5 A fake 'Victorian' ring. The casting 'fin' from the casting process runs right across the supposed hallmark.

Fig. 4. A silicon rubber mould and ‘casting trees’ as used for lost wax casting in the modern industry. Courtesy World Gold Council.

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indication of casting and thus would be a warning sign if seen, for example, on a 'Roman' gold ring or a 'Renaissance' gold pendant. However, careful observation is necessary so as not to confuse casting porosity with the localised porosity around soldered joints.

Wire drawing Gold is not only malleable; it is also extremely ductile. A single ounce of pure gold can not only be beaten to cover 10 acres, it can be drawn into a wire some 230,800 feet long. Nevertheless, as Gee thought fit to advise us some 60 years ago, this is according to theory and should not be attempted in practice.25

In antiquity wire had been made from sheet gold – as the Bible accurately tells us. Either strips cut from sheet were rolled or hammered to shape or thin strips were twisted and then rolled to compact them.26 The ancient tradition of using strips survived the change to mass production. As Hiorns notes in 1890, 'Chain-makers cast their metal [gold] in long and tolerably thick strips, which, when rolled to about Nos. 10, 1 or 12 of the Birmingham wire gauge, are annealed and cut into strips in the slitting mill, when they are drawn into wire.'27

The introduction of wire drawing itself was for a long time one of the most hotly debated subjects in jewellery studies. However, now it is generally accepted that the introduction of wire drawing, at least on a regular basis, occurred in the European/Mediterranean world between about AD 700 and 800.28 An introduction from the Far East is not impossible.29 The earliest types of wire drawing involved simply pulling the wire through perforations in iron or steel by hand, perhaps with ingenious embellishments to facilitate leverage. The next leap forward came with the introduction of the draw bench where a lever-system permitted much greater force and thus the production of larger diameter wires.

The drawbench was a medieval invention that might well have been encouraged by the increasing need for iron wire for chain mail. Wire drawing was a specialist industry. There were eight wire-drawing establishments in Paris by 1292.

Wire drawing with hydraulic power is variously attributed to Rudolf of Nuremberg or a Frenchman, Richard Archal, in about 1350 (and described by Eobanus Hessus in 1500).30 The influx of wire drawers into Britain from Saxony in the 1560s (led by Christopher Schultz, a French Saxon, according to some accounts) seemingly gave new impetus to British wire drawing.31

The eighteenth and nineteenth centuries saw little change in the wire drawing procedures used by goldsmiths, although the patenting of hard, gemstone-lined drawplates by William Brockedon in 1819,32 might have led to improvements in the regularity and perhaps surface characteristics of wire that could, in theory, be detectable.

Findings During the second half of the nineteenth century we find a growing industry of ready-made jewellery components or 'findings'. This was, in a sense, an expansion of the earlier supply of pre-formed gold and silver sheet and wire. In 1878 Wallis notes as follows:

At a comparatively recent date ready-made mountings for stones, produced


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by machinery, have been in use, not only in imitation but in real work. These are so contrived that the various portions of an article are cut separately and afterwards soldered together in such a manner as to receive the stones for fixing in the usual way. A still cheaper process is also in use, consisting of a strip of metal having a serrated edge. The proper portions of the strips of metal being fixed to receive the stones, the serrations are bent over to retain them.33

By the early 1880s it was recorded that ' A new industry ... is springing up for the supply of rolled or drawn metal to jewellers and dentists.34 The 1910/11 edition of the Encyclopedia Britannica notes that 'Machine-made settings have in recent years been made, but these are simply cheap imitations of true hand-made jewelry.'35

Die stamping The cast jewellery mass-production revolution of post-World War II years had been matched about a century earlier by the rapid adoption of die stamping. Die stamping, also known as stamping or machine-stamping, is a process which forms flat sheet metal into three dimensional forms in relief.

Two corresponding steel dies are cut, one with the pattern in relief, the other in intaglio (hollowed out). Sheet gold or silver is placed between the two and machine or hammer force presses the two dies together deforming the sheet into the desired shape in the process. The technique is used for making whole items or for component parts. Mechanical advances in the Renaissance included the screw presses used for die stamping precious metal Papal medals as evidenced at the beginning of the 16th century. Typical examples of die stamping today include the two halves of various earrings. A similar process, though with a cutting rather than shaping die, is used for cutting out shaped blanks of sheet metal, a bit like a cookie-cutter. Combined shaping and cutting dies are also used.

The use of patterned dies, formers and punches, with the necessary force applied by hand pressure or a hammer, is of considerable antiquity. However the true mass production metal stamping processes appeared in the wake of the Industrial Revolution. An early instance in the jewellery industry was a 1769 patent by John Pickering, a London jeweller for a machine for the stamping of ornaments in sheet gold, silver and other metals. 36

But although the mechanical stamping of ornaments, mainly base-metal buttons, began in the 18th century, the process only became common for costume jewellery in the mid-nineteenth century and perhaps was usual for precious metal jewellery until after around 1870. It was primarily a Birmingham-based technology and it helped establish that town as a centre of mass-production jewellery. Much mid- to late-Victorian period jewellery consists of stamped-out components assembled by hand.

Surface colouring Since antiquity it had been common to treat the surface of gold objects in such as way as to produce a higher purity, and often matt, finish. Wallis in 1878, referred to 'a method of finishing real gold work, which has been adopted of late years with marked success. This is known as "colouring", and without in any degree giving a fictitious appearance of value to the gold, it enhances the beauty effect.' There were

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so-called wet and dry processes, each with limitations regarding their usage, but both involved, again in Wallis' words, 'a chemical process by which the atoms of the alloy are subtracted from the surface leaving the pure gold alone visible.'37

The ‘dry processes’ could only be used with gold of 18 carat or above,38 and recipes employed in the latter nineteenth century – that match those used 2000 years earlier – included use of such mixtures of saltpetre, that is potassium nitrate, (2 parts) + alum (1 part) + salt (1 part) or sal ammoniac (1 part) + saltpetre (1 part) + borax (1 part). These mixtures were heated until liquid and the object, as highly polished as possible, was dipped and then dried. No further polishing or brushing was carried out.39 Gill observed in 1822 that:

It is a very curious circumstance, that the best workmen in this branch of jewellery have at this day no other menstruum for giving the last high finish in colour to their beautiful articles, than the employment of the compound salts of alum, nitre and common salt, wherewith to form a sort of aqua-regia, or niric-muriatic acid; instead of employing the nitro-muriatic acid itself – such, however is the fact.40

Gill also explains, accurately, that in such processes 'the copper, or silver, which entered into the alloy with the gold forming the articles, are dissolved, and the surface of the article appears of a true gold colour only.'

For objects of under 18 carat purity etching solutions had to be used, so-called ‘wet colouring’, although the basic chemical constituents were much the same. One recipe recorded by Hiorns as being used by a Birmingham jeweller consisted of 12 ounces of potassium nitrate and 6 ounces of salt dissolved in hydrochloric acid mixed with water in a ratio or 3:1.41 The object was dipped repeatedly and then scratch-brushed. As Hiorns notes, 'If the colouring has been properly conducted, a beautiful rich and dead colour will be produced.' The term 'dead' was used much like the word 'matt' today.

In the 1890s 15 carat was largely used for articles intended to made of 'coloured gold', that is chemically etched to give surface resembling pure gold.42 12.5 to 13 carat gold (around 52% to 54% pure) was the lowest that could be coloured by such techniques and such grades were extensively used for all kinds of jewellery – some even bearing imitation marks resembling official 15 carat marks.43 Since 12.5 and 13 carat gold could be dry coloured to look identical to 15 carat gold, it is not surprising to learn that in the 1870s 'If the reader were to take a walk down any of the principal streets of Birmingham, viz. New Street, Bull Street, or High Street, the vast majority of articles of coloured gold jewellery exhibited in the shops ... would be of this quality [13 carat], and marked as 15-carat fine gold.'44 Redman in 1883 was less apologetic - and tells us that 13 carat gold is about the usual kind employed in all respectable coloured-gold houses.45

12 carat and lower purity gold could not be wet or dry coloured and was thus only marketed in polished form and referred to in the jewellery trade as 'bright gold'.46 This probably explains why jewellers today can differentiate on sight so readily old 15 carat gold jewellery from that of poorer quality. 15 carat could bear a relevant hallmark, but this was seldom required. Indeed even 9 carat was not safe from debasement. Hiorns talks of gold objects of just under 9 carat which would still 'stand the test of nitric acid without exhibiting signs of corrosion.'47 While the 'ordinary' gold jewellery made in Pforzheim in Germany ranged from just over 3 carat to 6 carat, although finer quality was 13.5 carat and the finest 14 to 18 carat.48


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Of course, dry or wet colouring gold would give the surface a pure gold colour, thus minimising if not entirely removing any colour differences based on composition. This was advantageous for such practical purposes as disguising solder seams, but negated any aesthetic aspects based on variations of gold colour. We must thus assume that deliberately coloured golds were intended to be left in a polished or wire-brushed state. Such coloured golds included such things as 'brown gold' (20 parts gold, 4 parts copper) 'sometimes used by jewellers in decorative designs',49 a purple aluminium/gold alloy described in numerous places, including the Royal Mint report for 1891,50 or the gold alloys that had small additions of iron for decorative effect.51

For cleaning the surface of gold – often a process inseparable from surface colouring – various chemical mixtures like those just mentioned could be used. One very ancient 'cleaning solution' was based on urine. Even this tradition hadn't died out. The Penny Cyclopedia in 1838 noted that gold work was cleaned after manufacture with a mixture of urine and sal ammoniac.

The reference above to the surface treatment of gold with mixtures containing urine also brings to mind Rees statement that

Silver is tarnished superficially, by certain vapours, as that of putrefied urine, to a colour so like that of gold, that several edicts have been issued in France to prevent frauds of this kind with regard to wires and laces.52

While on the subject of surface finishing I can also point out that the abrasive polishing of high carat gold jewellery was uncommon. As Lewis pointed out in the 18th century, standard purity gold doesn't file easily and is better burnished than abrasive polished.53 This is equally true of ancient and medieval gold jewellery. However, when gold, typically of lower carat, was polished this was done using various iron compounds such as jewellers' rouge. In the 1820s we are told that a zinc/tin lap plus rouge was used to provide the beautiful 'flat' surface of gold and silver so much admired in the Geneva French watches.54

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2. Materials The materials which have been used for jewellery in the past are very wide ranging and include metals (precious or otherwise), glass (as imitation stones or enamel), minerals (gemstones and some fillers, polishing substances etc) and organic compounds (fillers, adhesives, textile or paper backings, human or animal hair, ivory, bone etc.). Modern man-made materials are also becoming more prevalent in forgeries. For example, in one recent case the 'niello' in an antique style ring was in fact a mixture of a cyano-acetate adhesive ('super-glue') and graphite (ground-up pencil lead).

Today fine examples of antique silver and goldwork from Britain and elsewhere are sought after and high prices paid. This, of course, has stimulated ever more sophisticated forgeries that, in turn, demand more and more sophisticated methods of detection.

One approach in forgery determination is to look at the constituents of the alloys, both of the individual parts of the object and the solders that join them together. The composition of these components of the article can provide the specialist with an indication of age and authenticity.

This technical approach has been most apparent in the field of antique silver and today most silver collectors, appraisers and dealers are at least aware of what are generally, and rather unspecifically, termed 'spectrographic tests' in the trade. Such tests essentially involve analysis to identify impurities in the silver that, potentially, can provide the dating evidence. This and the following chapters will cover, in non-technical terms, the background to such tests on silver and also their application to gold alloys. The methodology of the analyses will not be discussed (see, however, note 202).

Advances in analytical techniques led to an increasing number of analyses of silver artworks during the first half of the twentieth century. The value of the analysis results in considerations of origin and authenticity was soon realised and analysis become more common, although results were seldom systematically published.55

One major study in America, described in 1970, compared the composition of one hundred British silver objects of the seventeenth and eighteenth centuries with an equal number of similarly dated American pieces, including some forgeries and composite objects.56 Since then the analysis of gold and silver objects has become more and more commonplace and now many auction houses and specialist dealers are beginning to have antique precious metal objects analysed on almost a routine basis.

However, it is important to bear in mind that the composition of a gold or silver object can often prove forgery, but seldom should analysis alone be taken as proof of authenticity. It is often impossible to detect by analysis alone modern objects that by intent or accident have reproduced or reused gold or silver of earlier compositional types. The best that can be said is whether or not the composition of an object is consistent with that expected in genuine objects of the same purported period and origin. Analysis must thus be seen as an important adjunct to other criteria of authenticity such as style, details of construction, identification of tool marks, and, especially for antique silver, hallmarks.


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In Great Britain various individuals and organisations carry out analysis work on silver. The best known to the antique silver trade in Britain is the London Assay Office. This assay office, originally set up by goldsmiths to protect themselves against less than honest competition, now sees itself as having a secondary role in the 'protection of the public against the sale of spurious antique silver wares'.57 The protection takes the form of the Antique Plate Committee, formed in 1939, which will consider a suspicious object on the basis of combined stylistic and analytical criteria and advise the Assay Office as to whether it contravenes the Hallmarking Act.

As the above might suggest, the analytical approach is normally thought of as primarily for silverware and silver works of art. However, the importance for jewellery studies cannot be understated. The potential for dating gold alloys on the basis of trace element analysis is not as developed so far as it is with silver, but work to date appears promising. On the other hand it must not be forgotten that jewellery frequently contains silver components. Almost all antique diamond-set jewellery has silver mounts. With advances in micro-analytical methods, minute samples, even from a single claw holding a stone or solder from a joint, can be accurately analysed.

The composition of base metals in jewellery is outside my present scope – except where they are present as trace elements in the gold or silver. However, it is worth briefly mentioning the use of metals as enamel colorants that can thus provide some dating evidence for the enamels. Nickel, for instance, was first discovered in the 1750s and was occasionally being used as a colorant in glass by the end of the eighteenth century.58 Thus the presence of green enamel coloured by nickel in a purportedly Renaissance or seventeenth century jewel would raise an alarm.

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3. The Supply of Raw Materials

The precious metal from which jewellery was made could represent:

1. Gold or silver supplied by refiners or bullion dealer either as pure metal

for the jeweller to alloy as required, or ready alloyed to standard.

2. Coinage of the realm.

3. Scrap.

These will be considered in turn:

Metal supplied by refiners and bullion dealers Generally speaking, today, jewellers and silversmiths will work with newly refined and correctly alloyed precious metals purchased from bullion dealers. Even if, say, Granny's old teapot is taken to a silversmith for the silver to be used to made something else, the teapot is usually sold on as scrap and suitable new silver purchased in its place. This has probably been the practice at least since the latter part of the nineteenth century. Nevertheless, nineteenth and twentieth century silversmith's manuals still give methods for refining and alloying silver when 'exceptional circumstances' made this sensible.

Independent refiners and bullion dealers had existed in Britain from Medieval times.59 Such refiners would buy metal derived from mines at home or abroad or buy-up private or corporately owned gold and silver. Even the Worshipful Company of Goldsmiths sold off silver over the years to finance various causes, including both sides in the Civil War.60 On one occasion, as noted in the court minutes of the 22nd November 1637, the refiner William Gibbs, 'had offered a greater price than any other...' He paid 5/5 for gilt plate, 5/- for diet silver ingots [that is made from the scrapings retained from assays] and 4/11 for 'white plate'. The higher price paid for gilt plate demonstrate that the Mr Gibbs was quite capable of extracting the gold from gilded wares

In January 1693 'refiners of gold and silver' were among those who petitioned Parliament to permit the import of saltpetre (potassium nitrate) which was extensively used in the past in the manufacture of nitric and sulphuric acids.61 A statute of William and Mary in 1689 refers to the great advances made in the art of refining metals,62 but seems to have stipulated that all refined silver or gold had to be sold to the London mint. This would mean that the supplies to goldsmiths would be limited to existing stocks of plate, coins and, perhaps, to officially circulated ingots.

The eighteenth and nineteenth centuries saw the rise of major refining companies to provide for the ever-increasing demand. In the 1770s Matthew Boulton, the Birmingham silversmith, was purchasing 500 ounces of silver a month from the London refiners Robert Albion Cox.63 When in Birmingham in around 1850, Dickens visited a jewellery manufactory and asked "… whether the gold comes from California; but we find that it has just arrived – from a much nearer place –


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from a refinery next door.64

The Revenue Act 1867 applied excise duty on the annual license of every refiner of gold and silver. In 1878 Wallis noted that the various branches of the London jewellery trade included 12 masters and 46 workmen engaged in refining.65 The report from the Royal Mint for the year 1884 noted that much gold 'passes through the hands of recognised firms, who melt, and if necessary, refine it, and cast it into ingots of definite weight.'66 As the mint also recognised, although jewellers requiring modest amounts of gold often relied on coinage as raw material, 'large manufacturers purchase ingots in the market of a size convenient for their trade, and are able to retail metal to the smaller consumer.'67 The Mint officials even wondered if it should also offer to supply gold ingots to the public.68

We can probably assume that the silversmiths themselves were not generally expected to be capable of carrying out their own refining except in special circumstances.69 As evidence for this we can argue that if silversmiths in general practised refining, the change over from Sterling (92.5%) to the higher Britannia Standard (95.8%) in 1697 to prevent melting down of the coinage of the realm would have been senseless.

Precious metals could be supplied to jewellers as either refined (pure) metal or alloyed to the required standard. In early days the former seems more common. For example, a statute of Henry the VII in 1488/9 implies that refiners were only to sell refined silver and gold, not alloyed, and only to 'mints, changes and goldsmiths'.70 In later times it would seem that whereas gold was most often supplied in 'fine' form, silver could be supplied either pure or pre-alloyed to the necessary standard.

Matthew Boulton obtained 'fine gold' from his refiners,71 and a special committee report put before the House of Commons in April 1781 tells us that gold was always sold in pure state by the refiner, never alloyed and the alloy metal (i.e. silver and/or copper) was separately obtained. A century later, in 1878, we hear that 'gold is usually purchased by the manufacturer from the refiner, and then alloyed according to his own wants and standards'.72 Rees in 1819 tells us that the goldsmith 'ought to know enough of metallurgy to be able to assay mixed metals, and to mix the alloy.' Rees also notes that goldsmiths will mix gold, silver and copper so as to get the best colour and working properties.73

The supply of gold in pure form makes sense – the goldsmith might wish to use the gold in a variety of different alloys and standards. Remember that jewellers right up to quite recent times were not constrained to a limited number of carat standards for most of their work. Gem-set gold jewellery did not require hallmarking in Britain until 1975. In the past a wide variety of standards were used. For example, in 1819 Rees explained that the best gold for enamelling was 'ducat gold', that is between 23½ and 23¾ carats while Richardson in his Chemical Principles of the Metallic Arts gives various recipes for gold alloys for use by jewellers. One such alloy for 'ring gold' contained 1oz. 5 dwt 'gold coin', 6 dwt 12 gr 'fine copper' and 3 dwt 16 gr 'fine silver'. This would be just under 16 carat.74

On the other hand, the evidence suggests that silver was often supplied as sterling quality – not surprisingly since this was the overwhelming requirement. In January 1654 the Court of the Wardens of the Goldsmiths Company heard a dispute about 'standard' silver sold by a refiner to a goldsmith which turned out to be sub-standard. The Gentleman's Magazine in 1731 published a method to calculate the value of silver sold in bars and refers, in a given example, to 'standard [i.e.. sterling] silver in

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bars at 62 pence an ounce'.75 Charles Dickens, in his description of jewellery manufacture in Birmingham in the mid-nineteenth century, talks of 'an ingot which contains, to ninety-two ounces, ten pennyweights of silver, seven ounces ten pennyweights of copper', that is sterling quality.76

But this supply of Sterling silver was not invariable. In the early nineteenth century Gill actually noted that gold and silver were only sold in commerce in a pure state.77 We also have references to refiners selling fine silver to manufacturers in 1818,78 and in 1877 Gee refers to fine silver sold by refiners and bullion dealers.

If newly refined silver is unobtainable through official channels and the only sources are existing damaged or unfashionable silver plate or coinage, there will be a tendency towards a gradual debasement due to lack of raw materials. This has been assumed to be the cause of the debasement detected in Quebec silver during the period 1730 to 1864.79

Coinage Coinage had been a convenient raw material for silversmiths and jewellers from the earliest periods of coinage circulation. After all coins represented a ready supply of precious metal to the 'man in the street' in a form that had, at least in theory, an officially standardised (and enforced) weight and purity.

Wherever we turn, coinage crops up. A native jeweller in Hindustan in the first decade of the 20th century is quoted as saying 'The gold to be used is generally supplied by the patron or employer, and is frequently in gold coin.'80

In early centuries the prevention of the melting of silver coins had been approached from various directions. Henry II, in the early fifteenth century, tried to reduce the melting down of silver coins by fixing the price of worked silver.81 This measure might well partly explain the increase in the substandard silver that came into circulation at that period. An Act of Edward IV in 1477 forbade the melting down of gold or silver coin.82

In fact, an interesting variation on the usual coinage:silverwork relationship has recently been argued on the basis of 15th century churchwardens accounts from St Cuthbert's, Wells. Here silver rings given as offerings appear to have been held as reserve, not converted into money, and used to help finance building and even to provide raw material for repairs to plate. The reason being that rings were 'at least notionally of standard (.925), whereas much of the coinage in use probably was not'.83 Nevertheless, the high copper content of some fifteenth century silver articles has been noted.84

In the first half of the sixteenth century sterling remained the official standard for silverware, but English silver coinage – and thus presumably the raw material for some silverware – was debased starting with Henry VIII’s debasement to 83.33% fineness and falling as low as Edward VI's 25% purity.

In 1694/5 we hear how nobody could export bullion unless it was stamped at Goldsmith's hall, which could only be done when there was proof that no part of it had been obtained from coinage.

The Britannia Standard regulations introduced under William III in 1697 tried to prevent coinage being used as a source of raw material by raising the fineness required in worked silver from 92.5% to 95.8%. As was noted in Parliament in


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1696: 'It may reasonably be suspected that part of the silver coins of this realm hath been by persons regarding their owne private gain more than the puplick good molten and conferted into vessles of silver ...'. The enthusiastic use of silver by the public in the mid- to late-seventeenth century, which had led to this lack of coinage, is evident from parliamentary reports and other less formal sources. We hear, for example, that 'even publicans, who vend porter, are reduced to the necessity of having silver tankards, lest the delicacy of the drinker should be offended with pewter’.85 No wonder, another Act of William II provided that ‘no person keeping an Inn, Tavern or selling wine, is to expose in his house any plate except spoons.’

One idea mooted was simply another law to outlaw the melting down of coinage. However, Parliament finally introduced the higher Britannia Standard for silver objects which meant that coins could not be made into silver objects without refining and re-alloying. Such a refining process, as noted above, was presumably thought to be outside of the capabilities of the average silversmith. Of course, what this meant was that silver objects destined to be hallmarked had to be of the higher standard. It would be interesting to carry out an analysis programme to test the assumption that much silver jewellery and silver components of jewellery continued to be made from coin.

The Britannia Standard was repealed under George I, barely a generation later, since it was argued that sterling quality silver was 'more serviceable and durable' for most categories of objects. The economic pressure was also less because the low silver stocks of the seventeenth century had been largely replenished, to at least some extent by silver plundered from the Spanish. Indeed some 17th and 18th Century Cork silver made from Spanish dollars is actually stamped 'Dollar'.

Gold coins were a traditional source of raw material for jewellers. The gold coins of our period were the Guinea, minted until 1813, and the Sovereign that was minted from 1817 onwards.

Gee, for example, refers to 'manufacturing goldsmiths, who are constantly melting up the coin of the realm for manufacturing and commercial purposes.' He also notes that 'It is usual to melt down the coin of the realm.'86 However, Gee does says that the Guinea was used for wedding rings, but not for other jewellery,87 and certainly wedding rings were the primary jewellery product made from Sovereigns.

In 1878 Wallis noted a jeweller's raw material could consist of 'A few old coins, or for want of them some new ones', since: 'the character of the alloy of gold coin is well known, whether foreign or English, its purchase is a matter of considerable convenience to the manufacturer.'88 This is reflected in comments from the Royal Mint. The First Annual Report of the Deputy Master of the Mint in 1870 noted that 'It is to be apprehended also that working jewellers are in the habit of making use of large quantities of sovereigns in the business of their trade, owing to the convenience of being able to obtain by this means gold of a known standard; but it is difficult to point out in what way such a use of coinage could be prevented.'89 Similarly, the report from the Mint for 1884, noted that 'It is true that sovereigns may be used to a considerable extent by jewellers and others whose individual operations are not conducted on an extensive scale'.90

There were various reasons for this choice of raw material. One was simply economics: as Gee and Hiorns both recorded, it was slightly cheaper to use coins than buy the gold from the refiners.91 Gold coinage was worth its face value – £1. The sovereign actually weighed 123.27 grains representing a gold price of £3. 17s.

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10½d. per Troy ounce.

In one particular area of the trade, the use of sovereigns was not only usual, but actually established a tradition that has lasted into modern times. That is wedding ring manufacture. As Gee helpfully tells us 'there is one decided advantage which the wedding-ring makers have over other jewellers, viz. that the material - the coin - is sent with the order'.92 The use of sovereigns for wedding rings was also noted in 1890,93 and this custom helped establish the tradition of 22 carat gold for wedding rings which has survived into modern times. The insistence that, unlike most classes of jewellery, wedding rings had to be hallmarked, might well relate to this tradition and thus have been as a much a safeguard for the jeweller as for the customer – proving that the jeweller had neither debased nor 'clipped' the ring.

The gold coinage of Britain was traditionally of 22 carat gold with the alloy composed of 'one part of silver, and another of copper', as Rees noted in 1819. This changed to copper as sole addition in the late 1820s. Certainly this change had happened by 1829 and it is tempting to link it with the change of the Sovereign reverse from George and the Dragon to Arms within in a shield in 1826. There appears to be no precise record that these changes were connected, but the report from the Select Committee on Silver and Gold Ware in 1856 tells us that the older George and Dragon sovereigns were 'very white and nearly the whole of the alloy is composed of silver'.94 This was contrasted with the contemporary copper-containing coins where 'silver is never put in to make up sovereigns, it is only that which is found in the gold which remains'.

In 1838 we hear that both 22 carat coinage and 18 carat gold for 'ordinary jewellery' had only copper as the alloying material.95 This high copper content gave a distinctly rosy cast to the gold as is witnessed by many older wedding rings.

Nevertheless, the invariability of gold-copper for Victorian sovereigns is questioned by a remark by Assay Master Lutschaunig in 1872:

It also often happens that the 2/24 of alloy is composed of half a dozen different metals. This is owing to the fact that the Mint undertakes to coin any gold sent for that purpose, so long as the correct proportion of Gold is contained in the bars, and the metal is not brittle: it does not trouble itself about the nature of the 2 carats of alloy. 96

Australian sovereigns, from the Sydney mint, were alloyed with silver, not copper, but were of same weight, fineness and value as English ones.97

The melting down of coinage in the jewellery industry was not just a British problem, the British Jeweller of December 1914 reported that it was estimated that 'about one-half of all the gold coined in Germany is annually melted down for making jewellery. Whether the proportions were as high in Britain is uncertain, but in 1920 Stanley Baldwin noted his surprise that up to that time there had been in Britain no 'statutory power ... which prevents the melting up of coins'. He remedied this in his bill The Gold and Silver (Export Control, &c) act 1920. This stated:

It shall not be lawful for any person, except under and in pursuance of a licence granted by the treasury, to melt down, break up, or use otherwise than as currency any gold or silver coin which is for the time being current in the United Kingdom or in any British possession or foreign country.

In 1932 Neville Chamberlain was able to say that although it was against the


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national interest to hoard sovereigns and other gold coins, there cold be no reason to object to their sale 'so long as the law prohibiting the melting of gold coins was not contravened.'98 George Gee, in the preface to the second edition of his Goldsmith's Handbook, published in 1936, simply notes 'The melting of gold coins has been prohibited by the D.O.R Act since the last issue of this work.'99

A complete halt to the melting down of gold coinage was perhaps an empty hope. In 1946, during the period of austerity following World War 2, a black market in 22-carat wedding rings developed in Britain to satisfy those not content with the Government imposed 9-carat utility variety. As the Watchmaker, Jeweller and Silversmith noted in March 1946, 'Pirate jewellers with hide-out workshops' were paying way over the legal bullion price for gold sovereigns each of which could be melted down to 'produce two stylish rings'. Nevertheless, the Coinage Act of 1971 still stated that 'No person shall, except under the authority of a licence granted by the Treasury, melt down or break up any metal coin which is for the time being current in the United Kingdom...”

Unless gold of 22 carat was required – unusual in the nineteenth and twentieth centuries except in the case of wedding rings – the coinage had to be melted down and alloyed by the jeweller. Accurate recipes were published to facilitate this – for example those published by J. E. Collins in 1871.100

Since the official composition of the English sovereign had changed by 1829 from gold + silver + copper to just gold + copper, the composition of jewellery made from coinage, even if re-alloyed can sometimes be an indication of date. If sovereigns minted after about 1830, which have approximately 8.33% copper in them, are alloyed down to 18 or 15 carat, even solely with silver, they cannot contain less copper than about 6% and 5% respectively (even allowing for some loss of copper in melting and manufacture). On a similar basis, 18 and 15 carat gold alloys produced from pre c1830 sovereigns (containing about 4% silver) cannot contain less than about 3 and 2.5% silver respectively. These figures can provide some dating evidence for gold jewellery, but remember that gold sovereigns and other coins could be hoarded for generations and coins of very mixed dates can be combined.

The alloying possibilities for coinage were discussed at some length in the past. The economic savings that led to the adoption of gold-copper coinage alloys had been preceded by searches for other alternatives to silver in gold coinage alloys. As we will see below, zinc was one possibility, while in 1782 the possibility of using tin or 'regulus of cobalt' as alloying material was mooted in Parliament and special committees were set up to investigate.

Scrap The re-use of scrap or unwanted silver objects is common. Precious metals are the oldest 'green' consumer products in the world - constantly being recycled by remelting and reworking. An ancient Akkadian tablet of the seventeenth century BC excavated at Alalakh in Syria refers to the melting down of an old silver statuette in order to manufacture new objects,101 and the process has gone on ever since – both officially and unofficially. Other early documentary evidence includes the sixth century AD description of thieves stealing sacred silver from a Byzantine monastery and then selling it to a silversmith to rework into spoons.102 The silver chalice and paten obtained by another monastery in the seventh century was deemed unsuitable,

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despite its official stamps (the origins of our hallmarking) because, as it turned out, the silver had been obtained by melting down a prostitute's chamber pot.103 The theological explanation of this presumably apocryphal Christian predicament probably derived from Talmudic discussions as to whether silver vessels once defiled by contact with impure substances could be purified, in a religious sense, even by complete remelting and reworking.

When we turn to British silver of historical times we find much the same pattern of remelting and reworking. Watts, after collecting many documentary examples of both individuals and corporations recycling silverware, concluded that 'a large proportion of the silver produced for domestic purposes during the 18th century was obtained by melting down old family possessions'.104 Such behaviour led to Ruskin's lament that 'there would never be true art with precious metals if the maker expected his work not to survive more than a generation.105

It seems probable that the use of scrap gold and silver by goldsmiths was lessening by the nineteenth century and it was becoming far more usual for them to sell scrap to refiners and buy back refined metal.106


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4. Gold and silver Ever since a Mesopotamian ruler complained about substandard Egyptian gold and the Roman writer Juvenal scathingly referred to 'some trifle in silver of an inferior quality',107 the composition and identity of precious metals has been of concern to officialdom and public alike.

Gold Gold has very seldom been used by the jeweller in its pure state. It is normally found in nature alloyed with silver and often some copper, iron and other metals. For thousands of years gold was generally used 'as found' or alloyed with additional silver or copper for economic, practical or aesthetic reasons. It was only in about the sixth century BC, with the rise of gold coinage as an exchange medium, that refining of gold (purifying it) came into more general use. Gold coinage, after all, demanded gold in convenient form and of standardised weight and purity. Even after refining became widespread, pure gold was alloyed with silver, copper or sometimes other metals to render it more suitable for wear – pure gold is very soft.

Today, gold purities are described in terms of the carat. Pure gold is 24 carat, 75% gold is 18 carat and so on. The term carat comes from the Greek word Keratia, a small weight unit used for gold from about the beginning of the Christian era onwards. In about the 4th century AD the Keratia was defined as 1/24 of the then main Byzantine gold coin the solidus. Since the solidus was reckoned as being of pure gold, gold purities began to be described in terms of the number of Keratia out of 24 – the origin of our modern terminology. The description of gold purities in terms of the carat had reached Europe by the thirteenth century at the latest, having been in general use in the early Medieval Islamic World.

There had long been attempts to control the fineness used by jewellers and the 18th and 19th centuries were no exception. An ordinance of the Worshipful Company of Goldsmiths in 1729 ruled that 'no Goldsmith work, nor do to be wrote, no worse gold than the allay of 2 caracts, or six caracts (ie 22 or 18 carat); nor sett no glass in gold but good stones'108 However, from the time of George II in 1739 the precious metals used by jewellers were largely exempted from the necessity of being a fixed standard.

The setting of fineness standards for gold has seldom stipulated what the remaining components should be,109 but, generally speaking, it has almost always been primarily silver and/or copper. This was true for aesthetic and technical reasons - as Lewis noted in 1765, 'silver and copper are the only ones fit for serving as its alloy; all others debasing its beauty, and greatly injuring or destroying its malleability.'110 - In Britain this might well have been accepted trade practice with some general, but seemingly unfounded, assumption of legal proscription. This is perhaps indicated by a Special Committee Report put before the House of Commons on the 9th April 1781. This noted that copper was the best alloy for gold when hardness is required and added that to the best of the specialists witness's knowledge, gold for manufacture will not permit any alloy except copper, silver or a mixture of the two. Watherston in 1852 tells us that the alloy 'in silver should consist of copper only, and in gold of a portion of silver and copper'.111 The only clear legal stipulations that I am aware of were in Russia, Germany and Austria. In Russia gold could only be


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alloyed with silver or 'red copper', that is nominally pure copper, not brass or any other copper alloy.112

The gold alloys used by mints and jewellers throughout history were predominantly gold plus silver, plus copper, or plus both. The relative proportions of the silver and copper would reflect economics and aesthetics as well as being chosen to best suit the eventual working methods used. For example, Rees in 1819 noted that goldsmiths will mix gold, silver and copper so as to get the best colour and working properties.113

While the alloying of reasonable amounts of copper with gold had minimal effect on working properties, Gee did note that 18 carat with 75% gold, 25% copper was liable to cracking.114 Gold + silver + copper alloys were better. On the other hand, there could be serious problems if the copper employed contained traces of such impurities as lead, arsenic, tin, antimony and sulphur. Hiorns in 1890 warned that there could be traces of arsenic even in some electrotype copper, but 'It should be stated that the better qualities of commercial copper are now superior in purity to those manufactured forty years ago.'115

It is perhaps also necessary to briefly refer to white gold. Gold with enough silver present to give it a distinctly pale, greenish cast has been referred to a ‘white gold’ since antiquity and in 1883 Redman refers to 'white gold' of 12 parts of gold with 12 parts of silver.116 However, white gold in the modern sense is gold alloyed with a metal, or metals, such as nickel, zinc and palladium (and occasionally even manganese, tin and chrome) so that a grey, if not true white, colour results.

White gold jewellery alloys are typically a 20th century phenomenon and came into use as a cheaper substitute for platinum. The earliest white gold jewellery alloys were typically gold palladium alloys and these alloys have a long history. Gold-silver-palladium-copper alloys found use as bearing in good quality watches in the nineteenth century.117

Palladium white golds were being replaced by gold nickel-alloys by the 1930s- 'especially where cheapness is an important consideration', to quote Earnest Smith.118 Gold palladium alloys under about 18-carat purity don't have a good white colour and so lower fineness palladium white golds were seldom used. The nickel-gold white gold alloys also tended to lack whiteness under about 18 carat gold, and with too much nickel the alloys became extremely hard. Lower caratage nickel white gold often had considerable zinc contents – up to 20% in some 9 carat white golds. Zinc tends to make the alloy brittle and nickel can cause allergy problems and so alloys of gold with palladium are now back in favour. The various alloy ingredients in white gold can lead to greyish or yellow hues, particularly in lower carat alloys. Also colour changes can also occur as the result of manufacturing and assembly treatments. Thus white gold jewellery today is almost invariably rhodium plated. Colin Fink of Colombia University first described the electrodeposition of rhodium in 1933.119 The technology was adopted into the armaments industry, given impetus by World War II and in the first edition of Selwyn's Retail Jeweller's Handbook in 1945 he could refer to this 'later invention of rhodium plating' and comment on its use to finish white gold alloys.120

Until well into the twentieth century, some very debased gold alloys were used – down as low as 6 carats (‘bright gold’) in some cases. There were also precious-metal-containing base metal alloys, For example, 'Nurnberg gold' was a nineteenth century alloy of gold, copper and aluminium that was 'used in the manufacture of

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cheap gold-wares.'121

Silver When we speak of British Silver we actually mean silver of 92.5% or 95.8% purity, the so called Sterling and Britannia Standards. The setting of standards for the amount of silver in the alloy has seldom stipulated what the remaining components should be,122 but, generally speaking, it has almost always been primarily copper. In Britain in 1852, for example, Watherstone said 'the alloy in silver should consist of copper only', but this never seems to have been laid down in British law.123 In 1872 Lutschaunig noted that 'Silver is generally alloyed with copper'.124 However, a whole range of other elements can be present in the silver, including many in minute and unintentional traces.

The other metals mixed with the silver, whether as main constituents or as minute traces, will reflect a range of factors in the history of that silver – from the mine to the workshop. The choice of main alloying metals will be based on economics and practicalities – the resulting alloy must be of acceptable colour and tarnish resistance, but also must be most favourable for the type of processes to be used during its manufacture.


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5. Other metals present in the alloys, including trace elements

The trace elements present in the gold or silver will depend on numerous factors including the geochemistry of the original deposits and ores and the nature and efficiency of the smelting and refining processes used. In particular, the increased efficiency of the refining processes that were developed during the ninetieth century can often help us to distinguish nineteenth and twentieth century silver from that produced in earlier times.

As we saw above, the gold or silver from which a particular object was made could represent refined or specially alloyed silver supplied by a bullion dealer, scrap or coinage. Thus the impurity levels in the final object can reflect a bewildering range of factors through that silver's life.

In 1798 the Privy Council requested the undertaking of research into the possibilities of alloy in the coins of the realm. Experiments in adding numerous metals ended with little satisfactory results:

• Antimony destroyed ductility, and the same was true of zinc whether added as the pure metal or as brass.

• Arsenic adversely affected the colour and ductility of gold, even under 0.05%.

• Bismuth was disastrous to gold. • Cobalt when present as less than 4 grains per ounce had little effect on

colour or ductility. • Copper present in 1/12 proportions provided a perfectly ductile metal with

a fine red colour, but there were problems if the copper was not pure. • Iron in 1/12 proportions produced an almost white metal which was hard

but perfectly ductile. • Manganese adversely affected the colour and ductility of gold, even under

0.05%. • Nickel had minimal effect, • Lead was disastrous to gold. • Platinum in 1/12 proportions also gave a ductile metal, but it had the colour

of tarnished silver. • Tin, up to 8 grains per ounce had little bad effect.

The British copper and Swedish copper dollars as used in 'our mints as an alloy for silver' were no good for gold because of impurities such as lead and antimony. Fine granulated Swedish copper was best for gold. The report concluded that 'only two of the metals are proper to be employed to reduce fine gold to standard viz silver and copper' these could be used 'either separately or conjointly'.125 Nowadays, of course, trace elements are intentionally added to produce alloys with specific properties. For example, a small amount of cobalt helps grain refining in 14 and 18 ct alloys.126

Gold could be refined very efficiently, although this was not always resorted to. In 1890 Hiorns described a method used to make pure gold for a pure gold trial plate (to verify UK coinage), the resulting gold was 99.996% pure.127

Similarly, the silver trial plates can be exceptionally free of impurities. Some


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seventeenth century trial plates have low gold levels unmatched in coinage silver or plate until the late nineteenth century.128 This efficient refining was presumably deliberate – unless the silver used was a batch of Potosi silver with its characteristic very low gold levels (see below).

Generally pre-nineteenth century refining produced silver over 99% pure – the remainder being mainly traces of gold and lead. This refined silver was generally alloyed with copper to bring it to Sterling (or Britannia) standard. Various elements such as arsenic, antimony, bismuth, tin and zinc could be present in the copper, particularly the copper available to, and thus used by, smaller workshops. Such trace elements thus passed into the silver and can be detected by analysis. These impurities in the copper can render the resulting silver very brittle and a method of removing them was patented in Paris in 1859.129

Gold and lead are well known as trace elements that can be used to provide dating evidence for silver objects. Other trace elements that can sometimes provide useful information include zinc, nickel, cadmium, bismuth, arsenic and members of the platinum family of metals.

These trace elements are presented below in alphabetical order, not in order of abundance or significance.

Arsenic Traces of arsenic are found in some silver alloys and, potentially, in gold solders. Arsenic levels in silver are generally low, but several percent have sometimes been reported, particularly in solders. The arsenic is not homogeneously distributed in silver and, so far, has proved to be of little value in dating, although it has some value in authenticity studies and can help compare separate components of the same object, such as lid and base. Both Gee in 1877 and Hiorns in the 1890 describe the deliberate additions of arsenic to silver solder alloys.130 Hiorns notes that arsenic is sometimes added to 'produce great fusibility' and Gee tells us that some workmen refused to work with any other type of solder.

As late as 1908 Gee still notes that 'Arsenic is another substance occasionally employed in the preparation of solders. It easily unites with gold and silver and lowers their fusing points.'131 Note the mention of gold here. However, he does remark on its toxicity and that this was leading to abandonment of its use by goldsmiths. This might suggest that, as a rule of thumb, a noticeable arsenic content in a gold or silver solder would point to a pre-World War I date.

Arsenic in the main sterling silver alloy would generally be accidental. As the First Annual Report of the Royal Mint in 1870, and numerous other workshop manuals, tell us, even small traces of arsenic in silver caused considerable brittleness problems.

Bismuth Traces of bismuth occur in much ancient and antique silver and, like arsenic, probably derived from the copper additions. The deliberate addition of bismuth to silver alloys might seem unlikely at any period. However, we can note that recipes for solders for silver and other metals patented in 1864 did specify bismuth additions, as well as copper, zinc (as 'brass'), tin, and nickel (added as `German silver', that is a copper/nickel alloy).132

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Richardson in the late eighteenth century tells us that bismuth 'may be used for refining of silver by cupellation instead of lead.' This should at least be borne in mind in any consideration of bismuth in silver, although it seems unlikely that the process found use to any great extent.133

Significant bismuth traces have not been reported in antique gold. Bismuth is still a component of some modern low-temperature solders for precious metals.

Cadmium Cadmium is a common partner with zinc in nature and we thus find low but detectable cadmium in some antique precious metal alloys, including solders, which also have a relatively large zinc content.

However higher cadmium levels, or even low cadmium levels in gold or silver that have no detectable zinc content, is a strong indication of recent manufacture.

Cadmium was first isolated in the early nineteenth century, 1817 or 1818, and within a century was more often present than not in American and British sterling silver. For this reason a cadmium presence in precious metal alloys is a commonly used criterion in the authentication of antique and ancient silver and gold.134

The Penny Cyclopedia of 1836 notes that 'little use' had been found for cadmium, but that it could be combined with other metals to form fusible alloys. The alloys listed include copper/cadmium and, interestingly, platinum/cadmium, but these would appear to be metallurgical curiosities, not useful alloys.

The earliest reference to cadmium in gold or silver alloys for manufacturing purposes in Britain that I am aware of is a patent of 1862 communicated by A. Fontenay and H. C. de Ruotz, both of Paris.135

This invention consists in the formation of alloys of gold, silver, and copper with cadmium. The alloys of silver, copper, and cadmium, besides being useful for various other purposes, are particularly adapted for forming into wire by drawing, on account of their great ductility.

Some of the recipes given in the patent have up to 30% cadmium and the inventors noted that if the cadmium should volatise, the alloys should be melted again with more cadmium. The serious toxicity problems with the metal and its vapour were clearly not understood!

The extent to which cadmium was used in precious metal alloys or solders during the second half of the nineteenth century has not been studied in any detail, but it does not seem to have been common before the early twentieth century. The 9th edition of the Encyclopedia Britannica refers to alloys of cadmium with silver, gold and platinum, but makes no mention of their use in industry. Neither the 1870 nor the 1888 editions of Watt's Dictionary of Chemistry make any mention of cadmium in precious metal alloys. In Collins Private Book of Useful Alloys and Memoranda for Goldsmiths Jewellers etc. published in 1871 alloys of silver can include 'composition', 'brass' or 'spelter', but there is no mention of cadmium.136 Alder Wright in 1878, merely says that cadmium was 'occasionally employed for the production of very fusible alloys', with no reference to precious metal alloys.137 Then Hiorns, in 1890, refers to cadmium in various silver alloys (between 0.5% - 45%) and described 18 carat gold alloys which contained up to 12.5% cadmium (he also noted that the cadmium was volatile).138 Certainly the use of cadmium was


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increasing. A patent of 1894, for a solder for aluminium, contained cadmium plus a little silver139 and a year later we find descriptions of dental amalgams containing cadmium.140

The Birmingham goldsmith George Gee makes no mention of cadmium in his late 19th century books on precious metal working, but he does note the use of cadmium in solders and other alloys in a series of articles written in The British Jeweller in early part of the twentieth century. In 1908 he noted as follows:

Cadmium may also be used in the preparation of gold and silver solders to increase their fusibility, and it is considered a "trade secret" by those who use it, because it is not yet generally known to the bulk of the trade.'141

Gee also remarked in the same year:

Cadmium is now rather extensively used in the manufacture of sterling silver, being added as a deoxidant. It is customary to introduce 0.5 per cent. cadmium for that purpose. The cadmium renders the silver sound and the metal rolls well.

This mirrors what Hiorns had said in 1890 – cadmium imparts to silver greater flexibility and ductility without impairing colour.142

In 1916 an American patent described a sterling silver alloy with 92.5% silver and 7.5% cadmium.143 This was said to be suitable for tableware since it would not discolour after contact with fruit acids. Other justifications for the addition of cadmium to silver included facilitating spinning.

According to Smith, gold solder containing zinc and cadmium 'came into use as the result of the regulation issued by the Assay Offices in 1909 to the effect that the solder in 9 carat and 12 carat articles submitted for hallmarking must be of the same quality as the gold of which the article is made.'144

It would thus seem that the use of cadmium in precious metal alloys was first noted in about 1860, was occasionally used by goldsmiths after this date, though perhaps seldom before the 1890s, and only came out of the realms of protected 'trade secrets' around 1905 - 1910. Cadmium is falling out of use now due to its toxicity.

Gold as an impurity in silver The presence of a little gold had been noted in silver from quite early times. In 1823 we find the statement that 'It is a well-ascertained point in metallurgy that worked standard silver contains one-thousandth of its weight of fine gold'.145 However, these traces remained obstinately difficult to remove until a method of parting silver with sulphuric, rather than nitric, acid in platinum vessels was developed.

We find descriptions for the use of various mineral acids for precious metal refining from Medieval times onwards. In 1765 Lewis noted that the refining of silver with nitric acid removed copper, gold, lead, zinc and mercury from silver,146 but still some traces of gold and lead were left. Lewis also explained how aqua regia (a mixture of hydrochloric and nitric acids) would separate gilding from silver and reported the earlier eighteenth century experiments in France with what, in essence, would be aqua regia, for refining silver – a process which he optimistically noted removed all gold from silver.147 According to an early nineteenth century account, the use of aqua regia to refine silver produced silver that was ' perfectly pure, and even more pure than what is obtained by copellation [sic]'148

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The use of sulphur itself to separate small amounts of gold from silver is probably a very ancient process, perhaps dating back to Roman times. Lewis had noted it in the eighteenth century.149 Sulphuric acid had found some use in the refining of precious metals at least as early as the mid-eighteenth century. Nevertheless Richardson at the end of the eighteenth century noted that although hot concentrated sulphuric acid dissolved silver, nitric acid was the best solvent.150 However, the trend towards sulphuric acid was growing, indeed, the pioneers for an improved commercial manufacture of sulphuric acid (using lead rather than glass tanks) were Roebuck and Garbett, the precious metals' refinery in Steelhouse Lane, Birmingham – one source of supply for Matthew Boulton.151

Then we hear how, at the French mint in the early nineteenth century, the refiner M. Dizé experimented using sulphuric acid, not nitric, in the refining process thereby allowing the extraction of 'a portion of gold, which would otherwise be entirely lost'.152 The gold retrieval figure given is, again, 1/1000 parts by weight, that is 0.1%. In an article by Cadet de Gassicourt on refining gold and silver articles in Annales Generales de Sciences Physiques, he noted that whereas, formerly, the small gold content in silver was lost, this new refining process allowed its retrieval:

At present, 1000 kiliogrammes of silver give, by this process, one kiliogramme of fine gold, worth nearly 3500 francs, or about £150. Now if it be considered how many thousands of kiliogrammes of silver are annually cast in coin, in commerce and the arts, we shall be convinced of the immense advantages to the state, arising from the practice of the new method, for which we are indebted to messrs. Darcet and Lebel.153

This figure of one part gold in a thousand parts silver keeps cropping up in nineteenth century references, for example we are told that 'the advances made in the art of refining prove the possibility of extracting profit even to the 1/1000 part of gold from silver'.154

The great step forward in the general use of sulphuric acid for silver refining came with the innovative use of platinum vessels in the 1820s. Charles Dickens, in his fine description of a London refinery in the 1850s, describes these vessels:

[They] looked very much like large tin oil cans that would scarcely be worth cartage home... they were, however, made of platinum, and had cost from seven hundred to a thousand pounds a-piece.'155

With further regard for the economics Dickens comments:

…with the silver there is often a little gold, that will be worth getting out. The actual charge of the refiner for his operation on the gold committed to him is not very great ... but a great deal of profit comes from the habit among refiners of allowing nothing to be lost; they have the right of getting any silver that may be with the gold that passes through their pots, or getting any gold that may be had from the silver.

In 1856 a Parliamentary Select Committee reported that the old Spanish silver dollars had so much gold in them that it was common practice to melt them down to extract the gold and that the same was true with 'all the silver coinage made prior to the practice of separating the gold from the silver'.156 A few years later, C.W. Elliot and F.H. Storer similarly noted that gold was abundant in Spanish and US silver coins, less observed in English and Mexican and that there was little in French coin or in US fine silver.157 The Second Report of the Royal Mint for 1871 (published in


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1872) remarked on the noticeable amounts of gold present in the old silver coins then 'in the course of withdrawal'. This is proof that even as late as 1870 there was a considerable amount of eighteenth and early nineteenth century silver coinage still in general circulation and thus still potentially available as raw materials for silversmiths or jewellers. This is a point that needs to be borne in mind when trace elements are used in age determinations.

Almost all the gold (and lead) could be removed by electrolytic refining techniques. These came into use during the second half of the nineteenth century. There is mention of electrolytic refining for silver in Welsh refineries by 1870,158 but this technology did not become usual until Moebius patented his more efficient electrolytic method of refining silver in the 1880s.

Nevertheless, there are some low-gold silver ores around the world and these have provided silver with very low gold contents at various times in the past. Examples of such silver include some ancient Greek and Sassanian Persian objects and, most relevant to us, more recent silver originating in Bolivia.

There are some categories of quite genuine eighteenth century or earlier silver objects which, on the basis of their gold contents alone, would be assigned to the nineteenth century or later. This is not so much a problem with British silver, but is more frequent with some continental European silver. The 'blame' is usually aimed at Bolivia. Cerro Rico, the silver mountain, was discovered at what is now Potosi in Bolivia in the mid-sixteenth century. The mines here produced a vast quantity of silver that is characterised by a very low gold content, typically around 0.0001 to 0.005%.159 Certainly we begin to find silver coins with under 0.01% gold emanating from various Spanish mints after this date. A slight lowering of average gold contents in silver coinage from French mints at the same period time is also, perhaps, apparent.160 It would be interesting to analyse a series of the Cork 'Dollar' silver made from looted Spanish coin and plate.

The extent to which Potosi silver flooded the mints of Western Europe has possibly been exaggerated in the past, but Hamilton does suggest that a great deal of Potosi silver might well have passed to Germany to pay the Fuggers of Augsburg, bankers to the Spanish Crown.161 This might explain what appears to be a distinct dip in gold contents in some German silver in the generations following the mid sixteenth century – although silver originating from certain German mines is also a possibility.

Some later Spanish silver coins, as we noted above, had a remarkably high gold content. These presumably reflect ascendancy of Mexico as a major silver producer.

Low gold contents have been associated with galena and other sulphide ores of silver that might not have come into common use until the sixteenth century.162 In earlier times, simpler silver-bearing ores, such as cerrussite (lead carbonate), might have been more generally exploited. Such ores do result in the relatively high gold contents typical for much ancient and antique silver.163

As a general trend, there was a gradual decrease in gold contents in British silver from the sixteenth to early nineteenth centuries – perhaps due to the increasing presence of sulphide-derived silver among European silver stocks as much as to advances in refining technology. However a greater average gold content in the17th century might be attributable to increasing quantities of Mexican silver reaching Britain. Some seventeenth century silver can have well over 1% gold in it.

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There are several variables involved but, as a rule of thumb, the advances in refining methods mean that there is a noticeable reduction in the gold levels in British silver produced after about 1825-30. The gold content in UK Sterling before c. 1830 gold is usually from about 0.05% up to around 0.2% and sometimes well over 1%. After c. 1830 until the end of the 19th century it is usually under 0.05%

Indium The characteristic low gold content of silver originating from Potosi, in what is now Bolivia, has been noted above. Recently coin analyses have now shown that Potosi silver also has a small, but characteristic indium content of around 7 parts per million.164 A similar indium presence has been found in coins from Spain, France and Italy minted between about 1575 and 1650. Coinage from the same mints before and after these dates has higher gold and lower indium levels. Mexico replaced Potosi as a primary New World silver source in the mid seventeenth century. A research programme to look for indium in British silver coinage or objects might well be worthwhile.

Iron Iron is quite often found in traces in certain categories of silver and again mainly derives from the ores or smelting and refining treatments. However the effects of generations of butlers polishing silver with iron oxide based polishes (such as so-called plate powder and jewellers' rouge) should be borne in mind.

The intentional addition of iron to gold alloys for colouring effects has already been noted.

Lead Lead is a characteristic impurity in most antique silver. Elliot and Storer in 1861 observed that lead was more prevalent than gold in silver and probably derived from the refining methods used. They recorded the lead contents of various silver coins and found that these ranged from 0.3% in a Spanish dollar of 1793 up to almost 0.5% in a British shilling of 1816.165

As with gold, almost all the lead could be removed by the electrolytic refining techniques that came into common use in the 1880s - 1890s.

On the basis of numerous analyses carried out over the years we can say that as a guide the lead content in UK sterling silver before about 1830 is often, but not always, more than about 0.2% lead. After this it drops to typically 0.1 - 0.2% right up to the closing years of the nineteenth century.

Combining the information provided by gold and lead contents in silver we can obtain a surer guide to date and thus authenticity. At a minimum it is usually possible to say whether the silver was refined prior to the introduction of sulphuric acid parting in the 1820s-30s or after the general use of electrolytic refining in the 1890s.

Of course, correlating dates with compositions has to be carried out with an eye to alternatives. Reusing gilded silver can give anomalous gold contents and if the silver has been alloyed with scrap or commercial copper alloys rather than pure copper, all sorts of other elements, including lead, zinc and tin can find their way into the silver.


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This appears to be more of a problem in German silver, where a wider range of lower standards silvers were in use in past, than in antique British Sterling silver. Even so, lead can derive from things other than the original ore and the refining processes. One sixteenth century commentator on unscrupulous traders notes: 'Sometimes, or for the most part, you shall have tin, lead and the like mixed with silver.'166

Manganese Small amounts of manganese, often around 0.5%, have also been added to sterling silver since the early twentieth century, to act as a deoxidant, and, in conjunction with zinc, to reduce fire staining. Similar amounts of manganese are found in some twentieth century white golds and small traces of manganese have also been noted in some earlier silver.167 More research might be rewarding.

Nickel Nickel in gold

Nickel occurs with some gold in nature and has been noted in minute traces in some ancient gold. In addition some nickel might well have entered gold along with any alloying copper. However the deliberate addition of nickel to gold alloys is predominantly a twentieth century phenomenon with white gold. An obvious example is a recent case where one component of a purported seventeenth century diamond-set ornament proved to be made of a white gold/nickel alloy, the remainder of the mount was, as expected, silver of typical seventeenth century composition.

Nickel in silver

A minute trace of nickel can also enter silver alloys with the copper. In lower quality silver it tends to segregate with the copper and tin.

The presence of higher levels of nickel in silver can be of use in age determinations. Nickel was first discovered in the 1750s, but found little use prior to the nineteenth century. The alloying of silver with copper and nickel for use in jewellery manufacture is mentioned in British Patent number 1792 dated 1861. This was not for sterling alloys and in 1877 Gee noted that although various silver alloys could contain nickel (and zinc), these were typically the 'commoner qualities of silver', that is sub-sterling alloys.168

Such ‘commoner qualities’ of silver could include solders where I have detected up to around 3% nickel. Based on what we know of the development and use of nickel alloys, we can suggest that when such significant amounts of nickel turn up in silver alloys they would almost certainly point to an origin after the early nineteenth century.169

Platinum group metals The platinum group of metals comprises platinum, palladium, osmium, iridium, rhodium and ruthenium. The all, independently or in various combinations, turn up in gold and silver articles as impurities.

Platinum metals in gold

Various authorities noted the presence of platinum metals in gold during the 19th

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century, often in the context of the problems they caused goldsmiths.170 Dickens, writing in 1852, said:

We hear high praise of the Californian gold. It is so pure that some of it can be used, without refining, for second-rate articles. Some small black specks may be detected in it, certainly, though they are so few and so minute, that the native gold is wrought in large quantities.171

We can assume these specks were inclusions of platinum group metals, well known in Californian gold. In 1872 Lutschaunig notes that 'There are also other intruders that annoy the Goldbeater; and which are deadly enemies to malleability; Platinum, for instance, and the frequently-occurring Palladium, likewise the rarer Ruthenium and Iridium; all of which must be separated by melting with saltpetre.172

Particularly problematic were the small and very hard platinoid inclusions, predominantly osmium/iridium/ruthenium, which are presumably meant by Lutschaunig’s ‘Ruthenium and Iridium’. The reason these platinoid inclusions remain as specks in the gold is their insolubility in molten gold.

However iridium, osmium and ruthenium, the main constituents of the inclusions, have limited solubility in molten lead (this is not so true of platinum, palladium and rhodium). Thus we might expect the lead fire assay or cupellation method of gold refining to remove such platinoid inclusions. In this technique, the gold, is heated with lead, a flux (such as calcium carbonate or borax) and a reducing agent such as flour (which burns to form carbon). The lead melts and alloys with the precious metals while the base metals, plus the insoluble platinoids, remain as slag. The resulting lead button is then heated until the lead is oxidised to leave the refined gold or silver.

Recent estimates are that the lead refining technique would remove almost all any osmium present, some 50% of the ruthenium and 20% or so of the iridium.173 These are the removal rates for the individual metals so we can perhaps assume that the removal rate for alloy grains of these metals would be high, perhaps almost complete. On the other hand lead refining would not affect the presence of platinum or palladium which would pass into solution in the lead along with the gold. Indeed separation of platinum by lead was the basis of the platinum retrieval process invented by Deville and Debray.

Acid refining of gold using aqua regia and heat might also be expected to have the same effect – removing any platinoid inclusions (iridium, osmium and ruthenium) but leaving platinum and palladium.174 The effect of Lutschaunig’s ‘melting with saltpetre [potassium nitrate]’ essentially a nitric acid process has not to my knowledge been tried experimentally recently, but presumably worked to some extent.

Platinum is found in traces in gold from various mining regions around the world. It may well be of some potential in provenance studies and thus, as a knock-on effect, provide some information for age determination. However, little research has been carried out to date. Platinum itself found minimal use in European jewellery or fine metalwork prior to the nineteenth century and was uncommon until the twentieth. UK Hallmarking legislation ignored platinum until 1975 although the existence of the metal is noted in The Weights and Measures Act 1878.175

Palladium is a marker element of that can help in dating gold jewellery. Relatively high palladium levels are a characteristic of Brazilian gold.176 It has been noted that


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Britain absorbed almost a third of Brazil's gold output between about 1700 and 1760. Coin analyses have shown that prior to about 1703 the levels of palladium in British, French and Portuguese gold were well under 100 ppm. After this period they increase up several hundred, even up to over 1000 ppm by the mid eighteenth century.

The platinoid grain inclusions in ancient gold have been considered in some detail and their presence noted in some British goldwork right up to the twentieth century.177 There is still much research to be done. Why, for example, are such grains so common in Classical and Hellenistic Greek all-gold signet rings, but all but unknown in other jewellery of similar date and provenance? There is also the abundant presence of inclusions in Roman gold jewellery from Anatolia, but almost total absence in similar jewellery from Syria. Nevertheless, as far as we are concerned here, platinoid inclusions have proved so far to be of little determinative value in eighteenth and nineteenth century British goldwork.

Platinum metals in silver

When we turn to silver we find again traces of various members of the platinum group of metals – including platinum, palladium, rhodium and iridium. These are generally assumed to have passed with silver from the ores. However the present use of rhodium plating on some silver items might result in a rhodium content in some recycled silver in the future.

Platinum content has proved to be of some value in dating antique British silver, but its origin in it is still a little unclear. The platinum could be present in silver ores from particular mines and its relative abundance in the final object could relate to changes in refining processes. It is even conceivable that some platinum could derive from the introduction of the use of platinum vessels in the refining processes in the early nineteenth century.

One possible source of platinum-containing silver might have been Mexico – a major platinum producer. Mexico has been a major source of silver since the sixteenth century and by the eighteenth century was supplying probably two thirds of the world's silver. However, we can note that a feature of the Mexican silver mines in historic times was the use of amalgamation with mercury in the recovery process (rather than cupellation with lead). The amalgamation refining technique might be expected to remove most of the platinum present in the silver ores.

Of the platinum metals occurring in silver, iridium has been shown to be the most useful marker element for ore provenance studies and has been detected in various classes of silver from pre-Roman up to Georgian British.178 However iridium, if present, is usually only there in minute amounts, often 1 part in a million (that is 0.0001%) or less, and its detection requires complex and thus costly analysis techniques. Cupellation refining techniques would remove a proportion, but not all, of any iridium present, while refining with acid might remove most of it. 179

Tin Tin in gold

The alloying of tin with gold was probably never embarked upon commercially in the jewellery industry, although, again, some tin could enter gold with copper. The House of Commons Journal for 1st Feb 1782 says "Ordered, that a committee be appointed, to enquire into the divers expenses incident to and attending the coinage

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of gold alloyed with tin.'

S. Alchorne, the Assay Master of the Tower of London, experimented with various alloys of gold, silver, copper and tin. He found that gold alloys with as little gold as 80% plus 16.67% copper and 3.33% tin accepted hammering and rolling to 'the thinness of stiff paper, and afterwards working into watch-cases, cane-heads, etc. with very great ease.'180 This was disputed by M. Tillet in France who insisted that there was a serious problem with gold/tin alloys, particularly with annealing and that such alloys were not suitable for usual goldsmiths or jewellers' products.181

A note in the Chemical News in 1860 described how to refine gold that had been alloyed with tin or antimony. This records that some Australian gold contained up to 2% or so tin, but the writer was not sure if this was natural or added as part of some extraction or recovery process.182

Tin in silver

Tin is not uncommon in antique British silver, indeed it occurs right up to quite recent times, most typically in solders alloys. The tin is assumed to enter the alloy as an associate of the copper.

Deliberate additions of tin to sterling silver, even for fraudulent reasons, as recorded by Stubbes in the sixteenth century,183 as noted above, can hardly have been common. John Scasebrick, in his evidence to the Parliamentary Committee in 1773 stated that 'he had never met with any silver allayed [sic] with tin' in fact he assumed that it 'would not be malleable enough to bear the hammer, but would be too brittle'.184 However, tin does occur in some gold and silver solders (as noted by Hiorns in 1890 and Gee in 1908) and I have found up to 0.2% in 17th century sterling silver and smaller traces right up to the late 19th century. Smith, writing in 1933, says that 'the fusibility of silver solders is sometimes increased by the addition of tin.'185 He lists such solder alloys with up to 20% tin

Overall tin provides little chronological evidence, but as with other trace elements, tin levels can help to compare different components of what is purported to be a single, coherent object.

Zinc Zinc in gold

Zinc is very seldom found in early gold jewellery or objects because it is highly detrimental to the working properties of higher carat alloys.

Experiments were carried out on gold/zinc alloys during the eighteenth century. The effect on the malleability of zinc additions to gold was discussed at least as early as 1735186 and the injurious properties of zinc, lead, tin, bismuth and other metals were pointed out by Lewis in 1763.187 For example, following a Privy Council request in 1798, experiments were carried out which revealed that zinc, whether added as the pure metal or as brass, had an adverse effect on the colour and ductility of gold. This was not always detrimental – Lewis noted the possibility of using gold-zinc alloys for mirrors in the eighteenth century and such use is also mentioned in the Cyclopedia or Universal Dictionary of Arts, Sciences and Literature in 1819.

In gold produced prior to the nineteenth century any zinc present would generally derive from the employment of brass (a copper-zinc alloy) rather than pure copper


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as an alloying material. Due to the methods of manufacturing brass in the past, there were limits to the zinc levels attainable relative to the copper content. This means that in antique gold alloys, where the zinc entered the alloy in the form of brass, zinc levels will not exceed about 40% of the amount of the copper present. With advances in methods of brass manufacture and the possibility of introducing metallic zinc into the gold alloy, zinc levels in gold alloys after about 1800 can exceed the level of copper. The amount of zinc relative to the copper content is thus a useful guide in authenticity studies. However, in practice significant zinc proportions are only relevant for solders.

The use of metallic zinc in copper alloys (including precious metal simulants) first seems to become common in the late eighteenth century. The deliberate addition of metallic zinc to gold or silver jewellery, or jewellery solder, alloys does not appear to predate the early nineteenth century. Lewis in 1763 merely notes that goldsmiths alloyed the gold they were working with a little extra copper and silver, varying the proportions 'so as to make the colour of the solder correspond, as nearly as may be; to that of the piece.'

The earliest reference I am aware of zinc being added deliberately to a gold jewellery alloy is a solder recipe published in The Cyclopaedia or Universal Dictionary of Arts, Science and Literature of 1819.188 But even then this might not have been common. The Penny Cyclopedia of 1838 mentions solders for silver containing brass and zinc, but only alloys of gold, silver and copper for goldwork.

Spon in 1873 listed several solders for gold jewellery that had small zinc contents. One with 3 parts gold, 2 parts silver, 1.5 parts copper and 0.5 parts zinc, would 'flow at a dull red heat' and was 'suitable for gold brooches, guards, &c.'189 Another solder suitable for gold ranging from 12 to 16 carats contained 8 parts gold, 3 parts silver, 2 parts copper and 1 part 'good brass'.190

As stated, the presence of a little zinc in gold alloys facilitates their flow and melting. Modern gold solders, for example, can contain up to 12% zinc. The detrimental effects of zinc in gold – hardness and lack of malleability – were not so important with solders.

The earliest reference to zinc in general gold jewellery alloys I am aware of is Watherston's report in 1852. Here he notes that 'It has recently been found that gold of the quality of 11 carats, or less, if alloyed with zinc, instead of the proper quantity of silver, presents a colour very nearly equal to that of a metal at least 2½ or 3 carats higher.'191 Watherston also notes that 'a large quantity of jewellery has been made of gold alloyed in this manner'. This discovery of the fine colour of zinc alloys might have been very relevant in the debates leading up to the acceptance of 9 carat gold (37.5% pure) in 1854. Smith in 1933 said that because of their properties, 'it is agreed that zinc should not be a constituent of gold alloys of higher qualities than about 15 carat.'192 However there were also problems since in such alloys 'a galvanic action is produced, after a time, upon gold so alloyed, the effect of which is to split the metal into separate pieces, and render the article perfectly useless.' Cracking is still a problem with gold/zinc alloys and is one reason for the gradual abandonment of zinc as a whitener in white gold alloys.

In 1878 Wallis confirms that 'The modern use of zinc, in addition to silver, with the copper as an alloy, gives the manufacturer a greater control over the tint of the metal and enables him to adapt it to the special purposes to which it has to be applied.'193 Gee noted that zinc was used in 9 carat alloys and that it was 'employed by jewellers

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in the manufacture of bright gold alloys, as it gives liveliness of colour to their wares not to be equalled by any other metal.' He repeats Watherstone's note that if the proportion of zinc relative to silver in the gold alloy is increased the gold would have the appearance of one of 2 or 3 carats higher. He also comments that a gold/zinc alloy ' is very difficult to work, and after being some time in wear it changes colour.' Besides, more than about 4 dwt to the oz made the alloy brittle and unworkable.

The problems of hardness and brittleness encountered even in 9-carat alloys were at least partly associated with the traditional mechanical methods of manufacture. Even 9-carat gold alloys containing zinc were difficult to hammer, raise, roll or draw into wire. However, the same properties which encouraged the use of zinc in solder alloys – increased flow and easier melting – also made them ideal as casting alloys. Castability is improved by addition of about 2% zinc.194

As noted above, the detrimental effects of zinc in gold jewellery alloys were less evident in the lower gold finenesses than in 18 or 22 carat golds where the smallest trace of zinc could render them useless. We can perhaps assume also that the introduction of 9-carat (37.5%) and 12-carat (50%) gold in 1854 heralded the more general use of gold alloys containing zinc.

In the 1870s is was recorded that 'In later times gold has frequently been alloyed with zinc; especially in America...',195 and, as recorded above, Wallis in 1878 noted that a jeweller needed only gold (as coins) plus 'a few ounces of silver and zinc' as alloying material in order to commence business. (Assuming the gold coins to be sovereigns, their high copper content would presumably preclude the need for any additional copper).

Hiorns in 1890 made specific mention of zinc in the context of 9-ct gold alloys and in gold solder alloys, although he does note that it was still generally added to jewellery alloys as brass.196 Care had to be taken to ensure that the zinc or brass was free from lead.

Zinc in silver

Zinc is found in certain antique silver, particularly solders, with some regularity. In silver produced prior to the nineteenth century this zinc generally derives from the employment of brass (a copper-zinc alloy) rather than pure copper as alloying material. The zinc, which is usually fairly homogeneously distributed in the silver, though often depleted near the surface, can range from small traces up to quite high levels.

Several percent of zinc can be found in some Medieval and Renaissance silver and even in some more recent objects, particularly debased Continental silver and solders.197 However, most 18th and 19th century sterling alloys, have under about 0.02% zinc and very rarely over about 0.5%. Low but detectable zinc levels are not uncommon in British silver even of the present century. Zinc levels up to 5% or more occur in some antique silver solder alloys.

By the mid-nineteenth century we find reference to some non-solder silver alloys with zinc. The idea had been mooted in France prompted by the need to find alternative coinage alloys following the effect that the discovery of Californian and Australian gold had on silver prices.198 Various experiments with silver-copper-zinc alloys were carried out and it was noted that some French silver coinage contained 1% zinc and that some Swiss coins had for 'many years' contained some zinc as well


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as copper and nickel. In Britain the traditional Sterling quality of 92.5% fine silver for coinage was reduced in 1920 to 50% silver mixed with copper and a variety of other metals including zinc, nickel and manganese.

In the mid-nineteenth century we hear that 'some silver contains large quantities of zinc or nickel, because these metals used as alloy alter the colour but little'.199 Indeed, even recently zinc has been an intentional ingredient in sub-sterling silver alloys since it provides a good degree of whiteness. Some twentieth century Indian silver can contain more than 10% zinc. Such high zinc levels can make soldering difficult.

The level of zinc relative to the copper content is a very useful guide in authenticity studies on 18th century and earlier silver and gold objects. As noted above, zinc was traditionally introduced into the gold or silver alloy in the form of brass, that is a copper-zinc alloy. Due to the changing methods of manufacturing brass in the past, there were limits to the zinc levels attainable relative to the copper content. This means that generally in sixteenth, seventeenth and eighteenth century silver alloys zinc levels will not exceed about 40% of the amount of the copper present.200 With advances in methods of brass manufacture and the possibility of introducing actual metallic zinc into the alloy, zinc levels in silver alloys after about 1800 could be far higher relative to copper levels.

In practice, such considerations of copper:zinc ratios are only relevant for solders. In the late eighteenth century we find mention of metallic zinc in recipes for a variety of copper alloys, including precious metal simulants, but not, as far as I am aware, in precious metals themselves.201 However, as noted above, by the early nineteenth century, we begin to find reference to the addition of metallic zinc to precious metal solder alloys.

Solder alloys The frequent mentions of solders in what has been said about trace elements in gold and silver is important. The improvement in analytical techniques means that is now possible, and in some laboratories routine, to sample and analyse the solders on precious metal objects, even almost imperceptible solder seams.202 It is not unusual to find that the analyses of the solder joins are far more informative as to authenticity than the main alloy of the object. Solder analysis can be of paramount importance in cases where a faker or 'improver' has created an object by reassembling genuine, but disparate, parts.

Current British Hallmarking regulations stipulate that solder for sterling silver cannot be less than 65% silver and, indeed, this silver content of around two thirds has long been a common one. The main reason is that this is near to the eutectic of silver/copper alloys – that is, it has about the lowest possible melting temperature for any combination of these two metals. Thus we find solder recipes of two parts silver to one part copper in the writings of Theophilus in the twelfth century AD and in the manual by Cellini in the sixteenth century.

Descriptions of solder as being two thirds silver and one third alloy crop up in various assay masters reports in the eighteenth century203 and Richardson described a silver solder, though here for jewellers, that was made up of 19 pennyweights fine silver, 10 pennyweights brass and 1 pennyweight copper. This would produce a solder with a silver content of 63.33%.204 I have found just such solder compositions in late eighteenth century silver. That excess solder would adversely affect the

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overall quality of an object was recognised at least as early as 1423,205 and concern about unnecessary solder crops up time and time again in Assay masters' reports and the like from then on.

From the late eighteenth century onwards we find an increasing number of recipes for solders, in both workshops manuals and patents. The traditional components for gold solders are silver and copper (or brass), and for silver solders, copper and/or brass. As noted above, from the early nineteenth century onwards, we find solders with metallic zinc. Additions of tin are sometimes mentioned,206 although tin can also be an unintentional addition in the copper alloyed with the silver and, of course, from the later nineteenth century onwards, cadmium. As noted above, Smith dates the regular use of zinc and cadmium in solder for lower carats item to an Assay Office regulation of 1909.

As a result of the well known toxicity of cadmium and its classification as a carcinogen by the International Agency for Research on Cancer, the next few years will no doubt see the increasing use of cadmium-free solder alloys for silver and gold objects alike. The use of indium as a recently proposed alternative to cadmium should be borne in mind in what was said above about minute traces of indium in Potosi silver.


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6. The future In recent years there has been an increasing use of very sensitive trace analysis of historical gold and silver objects, looking for a wide variety of elements in addition to those mentioned above – including such metals as selenium and cobalt present in just a few parts per million.

The application of sophisticated statistical processes to the results of comprehensive trace element analyses have shown a quite extraordinary potential in grouping and dating of silver within the field of early Byzantine silver.207 It is envisaged that similar studies might be useful with other categories of ancient and antique precious metal objects.

Detailed analysis of gold and silver is not the only application of modern science to precious metals. Use of various types of microscope, including the scanning electron microscope, can help to characterise and define hallmarks, tool marks, and surface wear. This type of visual study can help supply answers to a wide range of questions, including:

• Is the engraving contemporary with the rest of the object?

• Is the apparent wear really due to long-term use and cleaning?

• Have the same variety of tools been used on different parts of an object – such as on base and lid?

• Are the hallmarks genuine?

The close study and characterisation of all aspects of hallmarks is of growing importance. It is not particularly difficult to produce counterfeit punches that can fool the casual observer and improving casting precision means that marks cast in situ are now often less easy to spot.

Changes in gold and silver with time are also being studied. Slight changes to surface compositional changes – the enrichment and depletion of certain elements – due to use and cleaning over long periods of time are being looked at and even minute internal changes in the silver structure are under investigation. One of the latter effects, in scientific terms the displacement of copper-rich phases at grain boundaries, is generally seen in ancient silver, but does not appear to exist - or at least be detectable with current equipment - in silver produced over the last five hundred years or so.208 Debased silver with higher copper contents, such as some German silver, might be worth examination in this respect. Similar effects in gold alloys are theoretically possible and might one day be possible to identify, perhaps first in ancient gold alloys with high copper contents.

With gold alloys signs of stress corrosion cracking can be a useful indication of antiquity when seen in higher carat alloys and in the absence of such metals as zinc.

The use of advanced science to examine what are, after all, art objects, designed to appeal primarily to the eye, has its critics. But, although the employment of science might be mainly aimed at detecting fakes, it is only through science that we can understand more about the development and changes in precious metal production


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processes. Only thus can we fully comprehend and admire the ingenuity and patience that has brought the crafts to where they are today.

We must also remember that methods for improving mining, refining and manufacturing processes for gold and silver engaged the finest scientific minds in the past. To divorce the art from the science is to belittle the ancient tradition of the goldsmith.

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References

1 For ancient goldsmithing techniques in general see J.M. Ogden, Jewellery of the Ancient World, Trefoil, London 1982. And various works cited below.

2 For Medieval goldsmithing techniques see J.M. Ogden, 'The Technology of Medieval Jewellery', eds. D. A. Scott, J. Podany and B. B. Considine, Ancient and Historic metals: Conservation and Scientific Research, (Proceedings of a Symposium organised by the J. Paul Getty Museum and the Getty Conservation Institute, November 1991), Getty Conservation Institute Malibu, 1994.

3 Book of Useful Trades and Library of the Useful Arts, New Edition, 1818, p. 22.

4 G. Wallis, 'Jewellery' in ed. G. Phillips Bevan, British Manufacturing Industries, 2nd ed. Stanford, London, 1878, p. 27.

5 C. Dickens, 'An Account of Some Treatment of Gold and Gems', Household Words, 97 (1852) pp. 449-455.

6 Wallis op. cit. pp. 15 – 16.

7 Dickens op. cit. (Treatment) 1852.

8 Wallis op. cit. pp. 15 – 16.

9 An early example is V. Zonca Novo teatro di machine e edificii, Padua, 1607. See A History of Technology Vol 3, C. Singer, E. J. Holmyard, A. R. Halland T. I. Williams, Oxford, Clarendon Press, 1957, p. 342.

10 J. L.Robsahm, Dagbok over en Resa i England, 1761, Folio 68. MS in Kungliga Bibliotek, Stockholm.

11 D. Diderot and J. d'Alembert, Encyclopédie ou dictionaire raisonne des aciences, des arts et des metiers, Briasson, Paris 1751-1757.

12 W. Lewis Commercium Philisophica-Technicum II History of Gold, Baldwin, London, 1763, pp. 38 - 229.

13 The Book of Useful Trades and Library of the Useful Arts, new edition London, 1818, p. 22.

14 Wallis op. cit. p. 28.

15 Wallis op. cit. pp. 48 - 49.

16 G. E. Gee, The Silversmith's Handbook, Crosby Lockwood, London, 1877, p 108.

17 A. H. Hiorns, Mixed Metals or Metallic Alloys, MacMillan, London, 1890, p. 307.

18 J. M. Ogden, 'Casting doubt: Economic and Technological considerations regarding Metal Casting in the Ancient World' In Material Issues in Art and Archaeology. Materials Research Society, 1991; J. M. Ogden. Interpreting the Past: Ancient Jewellery. British Museum Press, London, 1992. Preliminary research suggests that some use of lost wax casting for certain late 15th century British gold rings. This is about the same time that 18 carat gold (75% fine) became a recognised standard and some connection is a possibility.

19 Lewis, op. cit. reprinted in Technical Repository 5, 1824, pp. 304 - 314.

20 This might well lie behind the distinctly red, high-copper gold alloys that appear briefly in Egypt around the Amarna Period (c 1400 BC) solely for the massive 'stirrup' signet rings. The properties of such alloys would almost certainly point to casting


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rather than the hammering and soldering of bezel and hoop that was employed for the purer gold signets of similar form. The introduction of such red gold alloys might thus be seen as reflecting the adoption of a new technology as much as a new aesthetic.

21 Ogden, 1991 (casting), op. cit.

22 W. S. Prideaux, Memorials of the Goldsmith's Company Company between the Years 1335 and 1815, Vol. 2, Eyre and Spottiswood, London, 1897, pp. 246-7.

23 A. Selwyn, The Retail Jeweller's Handbook, Heywood & Co., London, 1945, p. 304.

24 Ogden, 1991 (casting), op. cit.

25 G.E. Gee, The Goldsmith's Handbook, revised edition, London, 1936.

26 J. M. Ogden, 'Classical Gold wire: Some Aspects of its Manufacture and Use', Jewellery Studies 5, (1991).

27 Hiorns op. cit. p. 307.

28 Ogden, 1991 (wire), op. cit.

29 Ibid.

30 Gee, 1877, op. cit. p. 114 and Gee, 1936, op. cit. p. 97. See also the Encyclopedia Brittanica, 11th edition, 1910/11.

31 Gee, 1936, op. cit.

32 UK Patent no 4395 of 1819. (see also Gill's Technical. Repository, new series 1 (1827)).


34 The 15th Annual Report of the Deputy Master of the Mint for 1884, 1885, p. 90.

35 The Encyclopedia Brittannica , 1910/11, 11th edition (under 'jewelry’).

36 UK Patent no. 920, 1769.

37 Wallis op. cit. p 39.

38 Gee, 1936, op. cit. p. 159; Hiorns op. cit. pp. 312 - 5.

39 Gee, 1936, op. cit. p. 148; Hiorns op. cit. pp. 312 – 5.

40 T. Gill, 'On Various Processes Employed in Jewellery', Technical Repository, 2 (1822) pp. 97-101.

41 Hiorns op. cit. pp. 312 – 5.



44 Gee, 1936, op. cit. p. 46.

45 W. Redman, The Jewellers' Guide, Bottomley, Bradford New Edition, 1883, p. 63.

46 Hiorns op. cit. pp. 294 –5.




50 The 22nd Annual Report of the Deputy Master of the Mint for 1891, 1892, p. 70.

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52 A. Rees, The Cyclopedia or Universal Dictionary of Arts, Sciences and Literature, London 1819.

53 Lewis op. cit. reprinted in Technical Repository 5 (1824) pp. 304 - 314.

54 Technical Repository 1, 18 (1822) pp. 432-3.

55 Examples of older publications illustrating the value of trace element studies of silver include – H. J. Plenderleith, 'Scientific Examination of an 11th Century Persian Silver Salver', Museums Journal 33 (1933) pp. 280 - 284; P.Coremans, 'De overblijfselen van het Sinte Geertruida-Schrijn te Nijvel: Chemisch en metallografisch onderzoek', Academie voor Wetenschappen, Antwerp, 1942; E. R.Caley, Chemical composition of Parthian coins, New York, 1955; R.J. Gettens and C.L.Waring, 'The composition of some Ancient Persian and other Near Eastern Silver Objects', Ars Orientalis, 2 (1957) pp. 83 - 90. More recent discussion of trace element in silver authenticity studies not cited elsewhere in this article include: Quebec and Related Silver at the Detroit Institute of Arts, Wayne State University Press, 1978, appendix; M. J. Hughes and J. A. Hall, `X-ray Fluorescence Analysis of Late Roman and Sassanian Silver Plate', Journal of Archaeological Science, 6 (1979) pp. 321 – 344: J.M. P. Cabral, M.F.D. Araújo and M.A. Gouveia, 'Aplicação da espectrometria de fluoresceñcia de Raios X na verificação da authenticidade duma Taça de Prata', Rev. Port. Quím., 22 (1980) pp. 71 - 75.

56 V. F. Hanson, 'A curator's Dream Instrument', in W.J. Young, ed. Application of Science in Examination of Works of Art, Research Laboratory, Museum of Fine Arts, Boston, 1973, pp. 18 - 30.

57 P. V. A. Johnson 'Assaying procedures at Goldsmiths' Hall for Hallmarking Purposes', in Precious Metals 1980, 2nd International Symposium of Sampling and Assaying of Precious Metals, San Franciso, 1980, ed. D. A. Corrigan and M. E. Browning, IPMI, 1980, pp. 147 - 57.

58 Richardson notes that nickel was 'not at present used in the arts ' but does say that 'It tinges glass a green colour' (this is, I believe, the earliest mention of nickel as a possible colorant for enamels), W. Richardson, The Chemical Principles of the Metallic Arts, Birmingham 1790, p. 149 - 50.

59 W.J. Cripps, Old English Plate, 10th Ed. London, 1914, p. 89.

60 J. B. Carrington and G. R. Hughes, The Plate of the Worshipful Company of Goldsmiths, 1926.

61 House of Commons Journal, 2 Jan 1693.

62 XXXI Wm and My c.30.

63 E. Delieb, The Great Silver Manufactury: Matthew Boulton and the Birmingham Silversmiths 1760 - 1790, Studio Vista, London, 1971.

64 Dickens op. cit.

65 Wallis op. cit. pp. 48-49.


67 Ibid.

68 Ibid.

69 In the early 19th century, for example, Gill describes methods of refining gold and


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silver for jewellers – T. Gill, 'On Various Processes Employed in Jewellery', Technical. Repository. 2 (1822) pp. 182 - 189.

70 Act 4, Hen VII c. 2 of 1488/9.

71 E. Delieb and M. Roberts. The Great Silver Manufactury: Matthew Boulton and the Birmingham Silversmiths 1760 – 1790, Studio Vista, 1971, p. 47.


73 Rees op. cit.

74 Richardson op. cit. (Also quoted in Gill's Technical .Repository 2, 1828, pp. 364 – 365.

75 The Gentleman's Magazine, 1 (1731) p. 110.

76 Dickens, 1852, op. cit.

77 Gill op. cit.

78 Prideaux op. cit. p. 318.

79 Report of the Canadian Institute of Conservation, quoted in N. Vallières, Art et Techniques de 'l'Orfèvrerie aux XViiie et XIXe Siècles, Musée d'Art de Saint Laurent, 1984.

80 Encyclopedia Brittannica 11th ed. 1910/11 under ‘jewelry’.

81 2 Hen VI, 1423.

82 Act 17 ED IV c.1. 1477.

83 N. du Quesne Bird, 'Rings as a store of Wealth in Fifteenth Century Wells'. Numismatic Circular, 102, 2 (1994) p. 58.

84 P. Glanville, Silver in Tudor and Early Stuart England, Victoria and Albert Museum, London, 1990, p. 397.

85 The Gentleman's Magazine, 32 (1762) p. 32.

86 Gee, 1936, op. cit. pp. 34 and 38.

87 Gee, 1936, op. cit.


89 C. W. Freemantle, The First Annual Report of the Deputy Master of the Mint, 1870, p. 24.


91 Gee, 1936, op. cit. p. 31; Hiorns op. cit. p. 291; Wallis op. cit. p. 19.

92 Gee, 1936, op. cit. p. 38.


94 Report from the Select Committee on Silver and Gold Ware, Parliament 3rd session 1856, volume 16.

95 Penny Cyclopedia, London 1838.

96 A. Lutschaunig, The Book of Hall Marks or Reference for the Gold and silversmith, John Camden Hotten, London, 1872, p. 129.

97 Gee, 1936, op. cit. p. 35 and Hiorns op. cit. p. 293.

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98 Parliamentary Reports, 10th March 1932.

99 Gee, 1936, op. cit.

100 J. E. Collins, The Private Book of Useful Alloys and Memoranda for Goldsmiths Jewellers etc. J. C. Hotten, London, 1871.

101 N. Nadav, 'The recycling of a silver statue', J. Near Eastern Studies, 40, 1 (1981) pp. 47-48.

102 Oxyrhynchus Papyri, no. 2419.

103 Georgius presbyter, Vita S. Theodori Syceotae, Chap 42. See C. Mango, The Art of the Byzantine Empire 312 - 1453, University of Toronto Press, 1986, pp. 143-4.

104 W. W. Watts, Old English Silver, London, 1924, p. 10.

105 J. Ruskin, The Political Economy of Art, quoted in W. Chaffers, Gilda Aurifabrorum, London, 1882.


107 Juvenal, Satires 9.


109 In Austria and Russia only silver or copper could be alloyed with gold - See Mrs. Brewer, Gold, Chatto and Windus, London, 1877, pp. 65 and 67.

110 W. Lewis, The Philosophical Commerce of the Arts, London, 1765, p. 115.

111 J. H. Watherstone, The Gold Valuer, Smith, Elder and Co., 1852, p. 59.

112 See Brewer op. cit. p. 67.

113 Rees op. cit.

114 Gee 1936 op. cit.


116 W. Redman The Jewellers' Guide, Bottomley, Bradford New Edition, 1883, p. 62.


118 E. A. Smith, Working in Precious Metals, N.A.G. Press, London 1978 (facsimile reprint of 1933 edition) p. 304.

119 D. McDonald and L. B. Hunt, A History of Platinum and its Allied Metals, Johnson Matthey, London 1982, p. 424.

120 Selwyn op. cit. pp. 53 and 320.


122 In Russia silver could only be alloyed with 'red copper', that is nominally pure copper, not brass or any other copper alloy – see Brewer op. cit. p. 67. In Austria a law of 1866 also stated that copper should be the only alloying material from silver – ibid. p. 65. In Germany only copper could be alloyed with silver – Hiorns op. cit. p. 329.

123 Watherstone, op. cit. p. 59.

124 Lutschaunig op. cit. p. 29.

125 C. Hatchett, 'Experiments and Observations on the various alloys, on the specific gravity, and the comparative wear of gold', Phil Trans Royal Soc, London, 1803.


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126 B. Ott, 'Gold Jewelery Alloys with Improved Properties', 11th International Precious Metals Conference, Brussels 1987, (IPMI ed. G. Vermeylen and R Verbeeck).

127 Hiorns op. cit. p. 308 –9.

128 J. S. Forbes and D. B. Dalladay, 'Metallic Impurities in the Silver Coinage Trial Plates (1279 to 1900)’, J. Inst. Metals, 87 (1958-9) pp. 55 - 58.

129 Patent by G. Ghesquiere, Paris, Oct. 1859, recorded in Repertory of Patent Inventions, enlarged series 36, 1860.

130 G. E. Gee, The Silversmith's Handbook, London, 1877, pp. 77 and 86-7, and Hiorns op. cit. p. 334.

131 G. E. Gee 'Science and Practice of Working Precious Metals', in The British Jeweller, June 4th 1908.

132 British Patent no. 418 of 1864.

133 Richardson op. cit. p. 149.

134 In recent years there has been a suggestion that cadmium could occur in some ancient gold solder alloys. This is generally rejected, for a summary see N. D. Meeks and P. T. Craddock, ‘The Detection of Cadmium in Gold/Silver Alloys and its Alleged Occurrence in Ancient Gold Solder’, Archaeometry 33, 1 (1991) pp. 95 - 107.

135 British Patent no. 1127, of 1862, via the London patent agent Charles Abel.

136 Collins, op. cit.

137 C. R. Alder Wright, Metals and their Chief Industrial Applications, MacMilllan, London, 1878.

138 Hiorns op. cit.



141 Gee, 1908, op. cit. His other references to cadmium include the same journal dated May 2 1908.

142 Hiorns op. cit.

143 US patent no. 1,191,890 of 1916.

144 Smith op. cit. p. 327

145 Cadet de Gassicourt's article on refining gold and silver articles first appeared in Annales Generales de Sciences Physiques which I have not been able to consult, but it was quoted in Rep. Art. Man. Agr. 2nd series 43, 1823.

146 Lewis, 1765, op. cit. pp. 90 – 91.

147 Ibid pp. 86 - 7.

148 'French account of the method practised in Birmingham Manufacturies for separating the silver from plated copper', in Repository of the Arts 2nd Series 23 (1813) p. 314.

149 Lewis op. cit. p. 161 ff. and passim.

150 Richardson op. cit. p. 108.

151 C. Singer, E. J. Holmyard, A. R. Hall and T. I. Williams, A History of Technology, Vol 4: The Industrial Revolution, Clarenden Press, Oxford, 1958.

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152 Gill op. cit.

153 Quoted in Rep. Art. Man. Agr. 2nd series 43, 1823.

154 Brewer op. cit. p. 19.

155 C. Dickens, 'Discovery of a Treasure Near Cheapside', Household Words, vol 6, no. 138, November 13th 1852, pp. 193 ff.

156 Report from the Select Committee on Silver and Gold Ware, Parliament 3rd session 1856, vol. 16.

157 C. W. Elliot and F. H. Storer, 'On the amounts of lead contained in some silver coins' Chemical News 3, 77 (1861) pp. 318 - 320 and 343 - 4.

158 C. Singer, E. J. Holmyard, A. R. Hall and T. I. Williams, A History of Technology, vol. 5: The Late Nineteenth Century. Clarenden Press, Oxford, 1958, p. 96.

159 See A. A. Gordus and J. P. Gordus, 'Neutron Activation Analysis of Gold Impurity Levels in Silver Coins and Art Objects', in Archaeological Chemistry, ed. C. W. Beck, Advances in Chemistry, series 138, American Chemical Society, 1974, pp. 124 - 147. Also D. A Scott, 'Technological, Analytical, and Microstructural Studies of a Renaissance Silver Basin', Archaeomaterials, 5, 1 (1991) pp. 21 - 45.

160 Gordus and Gordus, 1974, op.cit.

161 E. J. Hamilton, American Treasure and the Price Revolution in Spain, Harvard University Press, Cambridge, Mass., 1934.

162 D. A. Scott, 'A Technical and Analytical Study of Two Silver Plates in the Collection of the J. Paul Getty Museum', The J. Paul Getty Museum Journal, 18 (1990) pp. 33 - 52.

163 P. Meyers, 'Elemental Composition of the Sion Treasure and Other Byzantine Silver Objects', in ed. S. A. Boyd and M. M. Mango, Ecclesiastical Silver Plate in Sixth Century Byzantium, Dumbarton Oaks, Washington, 1992, pp. 169 - 190.

164 J. N. Barrandon, E. Le Roy Ladurie, C. Morrisson and C. Morrisson, 'The True Role of American Precious Metal Transfers to Europe in the Sixteenth to Eighteenth Centuries: New Evidence from Coin Analyses', in ed. D. R. Hooke and R. M. Gaimster, Trade and Discovery: The Scientific Study of Artefacts from Post-Medieval Europe and Beyond, in British Museum Occ. Papers, 109 (British Museum, London 1995) pp. 171 - 179.

165 Elliot and Storer op.cit.

166 P. Stubbes in Anatomy of Abuses in England part II - 1 Tricks of Goldsmiths and Vintners (1583), New Shakespear Society, Series 6, no. 16.

167 K. Randle, R. Wellum and J. E. Whitley, 'Radiochemical Determination of Trace Noble Metals in Silver Artefacts', J. Radiochemical Chemistry, 16 (1973) pp. 205 - 214.

168 Gee, 1877, op. cit. p. 42 and passim.

169 For nickel in base metal jewellery alloys see J.M. Ogden, 'Some Eighteenth and Nineteenth Century Jewellery Alloys', Jewellery Studies, 6 (1993) pp. 77 - 79.

170 J.M. Ogden, 'Platinum group metal inclusions in ancient gold artefacts', Journal of Historical Metallurgy , 11, 2 (1977) pp. 53 - 72.

171 Dickens op. cit. (Treatment) 1852.


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172 Lutschaunig op. cit. p. 33.

173 D. C. Bowditch, 'A comparative study of three analytical procedures for the collection and determination of gold and platinoids in precious metal bearing ores', Bull Austral. Mining Develop. Labs., (AMDEL) 15 (1973) pp. 71 - 87.

174 See Bowdich op. cit. and I. Palmer, G. Streichert and A. Wilson, 'The acid extraction of noble metals from low grade concentrates and ores and the subsequent determination of platinum, palladium, rhodium and gold', Rept. Nat. Inst. Metallugy (South Africa) 1218 (1971).

175 41 and 42 Vict c. 49.

176 Barrandon et al. op. cit.

177 Ogden, 1977, op. cit.

178 e.g. A. A. Gordus, 'Neutron Activation Analysis of Streaks from Coins and Metallic Works of Art', in W.J. Young, ed. Application of Science in Examination of Works of Art, Research Laboratory, Museum of Fine Arts, Boston 1973, pp. 9 - 17. For an example of iridium in British Georgian silver see Randle et al. op. cit.

179 Bowditch, op. cit.

180 Reported in Rep. Arts and Manufacturies 7 (1797).

181 See Rep. Arts and Manufacturies. 9 (1798) pp. 275 - 282 and 346 - 358.

182 M. Warington in Chemical News, 1, 8 (1860).

183 Stubbes op. cit.

184 See C. H. Jackson, English Goldsmiths and their Marks, 2nd ed. London, 1921, p. 359.

185 Smith op. cit. p. 337

186 M. Hellot in French Memoirs (sic) for 1735 as quoted by Lewis but I have been unable to identify this source.

187 Lewis, 1763, op. cit. pp. 38-229.

188 Rees op. cit.

189 E. Spon, Workshop Receipts [sic] for the Use of Manufacturers, Mechanics and Scientific Amateurs, Spon, London, 1873, p. 364-5.

190 Spon op. cit. p. 366.

191 Watherston op. cit. p. 63.

192 Smith op. cit. p. 326.


194 Ott op. cit.

195 Brewer, 1877, op. cit. p. 17. See also Collins, op. cit.; Spon, op. cit., p. 364 and Hiorns op. cit. p. 333.

196 Hiorns op. cit. pp.. 295 - 6, 334 et passim.

197 For zinc in Renaissance silver see Scott 1990, op. cit. and Scott 1991, op. cit.

198 E. Peligot, 'Sur les Alliages d'argent et de zinc', Annales de Chimie et de Physique, 4th series, 2 (1864) pp. 430 – 438: Hiorns op. cit. p. 321.

Jack Ogden

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199 Brewer op. cit. p. 17. See also Gee, 1877, op. cit. p. 46.

200 See, for example, P. T. Craddock, ‘Medieval Copper Alloy Production and West African Bronze Analyses - Part 1’, Archaeometry 27, 1 (1985) pp. 17 - 41.

201 Richardson op. cit. pp. 165 - 170.

202 In the technique preferred by the present writer (while director of the Cambridge Centre for Precious Metal Research), the samples are removed under a binocular microscope using a very fine, very sharp scalpel blade. The samples are minute, typically far smaller than the full-stop at the end of this sentence, and it is usually possible to take samples from solder seams or even from the hallmarks. The ability to obtain information from minute samples is particularly important with jewellery where, for example, the mounts of much antique diamond-set jewellery are of silver. After suitable mounting and preparation (often the trickiest part of the operation) the samples were analysed using wavelength dispersive X-ray fluorescence analysis. A whole variety of other techniques are of possible application including PIXE. Atomic Absorption Spectroscopy and Inductively Coupled Plasma Spectroscopy are also being routinely used, but these generally require too large a sample for many applications - particularly for solder analysis or multi-analyses on one object.

203 See Jackson op. cit., p. 358.

204 W. Richardson, 1790, op. cit. , p. 168.

205 Act 2 Hen. VI. c. 14.

206 G.E. Gee, Gold Alloys, Crosby Lockwood & Son, London, 1929, p. 83.

207 Meyers op. cit.

208 Scott, 1991, op. cit.

Age & Authenticity: The materials and techniques of 18th and 19th century goldsmiths

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Transcript of Age & Authenticity: The materials and techniques of 18th and 19th century goldsmiths