Silverplate, Silverplating. Depositing a layer of silver on a piece of base metal by the process of electrolysis. Formerly such items that were given a coating of silver by firesilvering before the development of electrolysis in the 1840s. While not as widely used as gold coating or gilding, silver coating was done for the same reason: to reduce cost. An object could be fabricated in base metal then coated with gold or silver. However, since silver, historically, was not that relatively expensive, small objects intended to be silver in color were usually made in solid silver without the need of additional process of silver coating. It was the award industry, particularly for sports medals, that demanded a cheaper silver medal and silverplating filled this need for a low cost silver class of award medals.Silverplating an object gives it all the characteristics of silver, except for fineness (it is not solid silver). These characteristics most notably are color, hue and texture of silver. There is no difference in patina finishing between a solid silver object and one that has been silverplated. Very small objects, as charms and medalets, are almost never silverplated; it costs less to strike them in silver than the additional expense and care of conducting the silverplating.Silverplating is a hard, permanent coating on any base metal. It is not the same as SILVERED, which is a less permanent dip coating (in silver cyanide, like the processof silvering mirrors). Silvered medals, for example, will loose their luster and darken in time. Silverplated medals exhibit slightly better wearing qualities than solid silver or sterling and retain their luster (but when damaged they expose their base metal).History of silverplating. Coating with silver had an ancient origin; like firegilding, firesilvering coated objects by the use of an amalgam of mercury. Even though the process gave off mercury fumes – deadly to those workers who breathed the fumes – the process was in use until the invention and development of electrolysis, despite the shortened lives of such craftsmen.Firesilvering was a very thin coating of silver on a base metal. For the first third of the 19th century a thicker "plating" was accomplished by soldering thin sheets of silver to the base metal then hammering this to the required thickness. Thus was called close platin (and perhaps could be considered a forerunner of clad, cladding). It ceased with the invention of electroplating, however.Based on the first discovery of an early form of electroforming by a German, Moritz Jacobi in 1837, two Englishmen, George Richards and Henry Elkington, were able to patent silverplating in England in 1840. The first electrolysis was accomplished with primitive batteries, which continued in use for four decades. With the advent of commercial electricity in the 1880s the process was modernized, cost was reduced and plating by electrolysis became widely available. It spread quickly through the tableware industry, the jewelry industry and to a very small degree, into the medallic field.Preparing an object for silverplating. The object to be plated must be thoroughly cleaned, then dried and baked. While many metals can be silverplated, a few – notably copper, bronze, brass, nickel – require a precoating to prevent peeling (or lifting), an anomaly where the silver plate does not adhere properly to the base metal surface. The process is called quick-silvering and consists of swabbing the cleaned metal surface with a solution of perchloide of mercury and sodium cyanide. The metal is then placed immediately onto a rack and immersed into the silverplating tank.Technique of silverplating by electrolysis. Pure silver must be used as the anode. The work to be plated is prepared as the cathode and the anode and cathode are wired to conduct electricity. The two are immersed in a tank filled with a silver electrolyte (a solution in which free silver ions are suspended). When the electricity is turned on a low voltage current runs through the anode of silver, leaching positive charged ions of silver into the liquid electrolyte solution.These ions are attracted to the cathode because it is negatively charged. As long as the current is on this becomes an on going process: ions exiting the anode, become suspended in the electrolyte, existing ions deposit on the cathode (the work to be plated). The current returns to the rectifier to complete the circuit.By electrodeposition the silver builds up slowly, a little at a time, on the cathode (the piece to be plated). Under proper conditions of time, temperature, strength and freshness of the chemicals – there are many variables – the proper thickness builds uniformly on the cathode pattern. Flash plating takes place quickly (the silver color becomes evident in two to three minutes); a typical medal could be plated in an hour or so. Heavier silverplating, or the addition of another metal like rhodium for strength, or nickel for hardness, requires additional time and processing, often in a separate plating tank. See electrolysis, electroplating.Silverplating widely used in jewelry manufacture. The tableware industry did the most to develop silverplate technology, but it was the jewelry industry to make the widest use of it. Objects could be fabricated in copper alloys at low cost, then silverplated; such items could sell for a fraction of the cost of similar items of solid silver or sterling.Nontarnishing silver was also a development of the jewelry trade. Since much of their silver were objects to be worn, jewelry items were bright plated. This was accomplished by alloying silver with cadmium or a tiny plating of rhodium or palladium to the final surface of the object.Likewise medals could be struck in copper or bronze and be silverplated to look like solid silver. Modern medals were first silverplated in jewelry factories well before they were silverplated on medallic firms. It should be noted that, generally, national mints do not silverplate any of their medals (and certainly not coins!) preferring instead to issue only solid silver, silver alloy or silver clad compositions. (Mints have silverplated copper pattern coins, however; copper U.S. Trade dollar patterns of 1873 were silverplated to observe their appearance in silver.)Silverplated markings. Unlike precious metal objects, which are required by law to be marked with a fineness, silverplated objects are not required to be marked in any way. They do not reflect the heritage of hallmarking that developed in the 16th century to identify precious metal items from those that were not – the clad, plated or imitation items. While silverplated items do not have to be identified, some high quality medals will identify the base metal. Thus any item edgelettered "bronze" for example, but in silver color, must be assumed to be silverplated.Caution should be noted for some items presumed to be plated. Latin American items marked "plata" are not plated, but are indeed silver as this is the Spanish word for silver.Also some 19th century items were marked with one or more Xs; a single X meant silverplated, XX or XXX meant a heavier silverplate.Large silver medals – as any silverplated object – are susceptible to test cuts, an attempt to learn of the base metal. Worn silverplated medals may reveal the base metal by the color showing through – bleeding.Copywriters for private mints in the last quarter of the 20th century gave rise to new language for silverplated medals. These limited editions were described – and even edgelettered – "layered in fine silver" or "layered in pure silver." These all mean silverplated. There is no comparable word for silverplated as there is for goldplated, vermeil.How to tell silverplate from solid silver. First look for any markings. Some silver medals were marked with hallmarks, particularly those struck in the British Empire.A silver medal with a hallmark is obviously a solid silver (or sterling) medal and not one that has been silverplated. All precious metal objects must by law identify their fineness (after 1904 in England, 1906 in America). Generally precious metal objects made in other countries follow this same practice.If the medal is not marked it can be identified by a nitric acid test. The nitric acid cannot be applied to the surface: silverplate will give the same results a solid silver. A test cut must be made and the nitric acid applied to the base metal revealed there. However, the best test is one of specific gravity, where solid silver will reveal a higher number than a silverplated item.Reverse silverplating can occur by changing the electric current in the electrolysis tank. The work becomes the anode; the silver is stripped off to deposit on the cathode. The stripping can be done right down to the base metal.Imitation silverplating can be accomplished by a silver tinted lacquer.
excerpted with permission from
An Encyclopedia of Coin and Medal Technology
For Artists, Makers, Collectors and Curators
COMPILED AND WRITTEN BY D. WAYNE JOHNSON
Roger W. Burdette, Editor