Silver overlay is the electro-deposition or plating of silver on ceramic and glass objects. Also known as silver deposit (and deposit ware) the process is essentially the same as electroplating silver onto metal forms; a practice which had first been achieved by the Elkington Company of Birmingham, England in the late 1830s. However, there is a major difference when plating is done on glass and ceramic surfaces because they are very poor conductors of electricity. In order for silver to be attracted from a negatively charged silver solid, thorugh a chemically conducive bath to a positively charged object of ceramic or glass, it must be coated with a metal-based flux. Flux has many varied contents, but John Scharling's silver overlay patent of 1892 calls for a base of silver nitrate.
A second significant difference between overlay and metal to metal plating is that the obejct with overlay, in general, is to enhance the ceramic or glass with silver but not encase it completely. The discreet placement of silver was achieved by two principal methods; the first is a reductive process, partially illustrated in the pair of photographs next to this panel. On the workbenches in these photos are ceramic and glass objects which has been entirely coated with flux, then placed in the plating bath, coming out completely coated with silver. The artists are shown painting on these silver-shelled objects with thick, black "resist" varnish. With the resist design complete, the pieces will be returned to the electroplating bath. The current is reversed, and any silver not covered by the varnish is dissolved and returns to the positively charged pole. The second method for depositing silver on discreet areas is an additive process. The flux is painted on in the design desired then the object is plated, with the silver being attracted on to the fluxed areas.
In each of these methods, finish detailing is done by engraving. The plating bath is used to aid the engraving process, removing silver to a further depth where the graver's tools have removed the resist varnish.
Silver overlay was produced by many silver companies. This exhibition contains work from seven American firms: Alvin Corporation, Electrolytic Art Metal Company, Gorham Manufacturing Company, George A. Henckel and Company, La Pierre Manufacturing Company, Matthews Company, and Rockwell Silver Company. By no means is this an exhaustive list of silver overlay makers, either in America or abroad. Although there is no work in this exhibition which can definitely be assigned to a European firm, there are two well-known makers discussed in the catalogue: Max Schwarz of Vienna and Oscar Pierre Erard, a French artist working in Birmingham, England.
Erard's name is one associated with the invention of silver overlay, and he did hold patents related to the process. In America, at the time, Edward A. Thiery, Charles F. Croselmire and John F. Scharling all of Newark, New Jersey, were also awarded patents having to do with silver overlay. The first American patent, filed by THiery and Croselmire on September 3, 1885, was entitled "Article of Jewelry and Method of Ornamenting Same" and describes "a base of glass, crystal, or any other transparent or translucent substance." The patent describes depositing "thereon by electrolysis the metal which is to form the seamless coating." It is curious that no American maker of silver overlay wares marked their work "patented" except for the Alvin Corporation, yet not patents held by Alvin or any person associated with the company have been found. The company was founded and oeprated in the Newark, New Jersey area and may well have known the patent holders mentioned above; but, no formal transfer or assignment of patents is known, and this remains one of the mysteries of the invention of silver overlay.
A company di dnot need patents to make silver overlay. Indeed, Providence's own Gorham Manufacturing did not hold any such patents and was one of the most prolific producers of overlay wares. In this exhibition there are 16 pieces by Gorham, 13 in the Gilson Collection and 3 from this museum's own collection, on view behind you in this gallery. Included among the Museum's pieces are a remarkable pair of whiskey decanters made for Gorham vice president John S. Holbrook. The customized design for these one-of-a-kind objects have Holbrook's initials worked into overlay design, rather than simply engraved in the silver, as was usual. These decanters are part of the largest public collection of Gorham silver, presented to this msueum by Textron Inc. in 1991.