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ELECTROPLATING
Like gilding, electroplating is a means of depositing a fine layer of quality metal over cast and wrought designs. Metals suitable for use as electroplate include chromium, nickel, gold, silver and copper to name a select few. The plate is carried in a bath solution as a metallic salt. If an electrical current is passed across terminals in the bath, the suspended metallic content is attracted to the negative pole or CATHODE By connecting a cast to the cathode and regulating the electrical charge that passes from the positive pole (ANODE), a precise deposit of plate of up to about 75µm, can be built up. By attaching a sculpture to the positive pole (anode) instead of the negative cathode pole, the process can be reversed and the plate removed from the cast’s surface. This latter effect also forms the basis of a technique used in restoration workshops to clean encrusted metallic deposits from distressed artifacts (in this case by attaching the damaged sculpture to the negative [cathodic] terminal of a low voltage DC supply and immersing in a 1% sodium carbonate electrolyte).
Electroplating is most effective when done using salts containing a high purity metal (as opposed to those of an alloy composition) – though plating is theoretically possible with a brass or bronze bearing electrolyte (both alloys of copper), as well as tin, nickel and zinc alloys. The contours and forms in some sculptures may render them unsuitable for an electroplating process, this often applies to designs which contain deeply undercut recesses or acute internal angles.
Any cast destined for electroplating must first be finished to a very high standard. This generally means finishing the cast’s surfaces to a mirror polish standard. Any minor faults and unevenness evident in the cast become highly visible once an electroplate deposit has been applied. With these factors in mind, considerable attention must be paid to both the features incorporated within a design, and surface quality of the cast (see for example the plate finished works of the sculptor Ernest Trova [1927-]).
As well as plating items formed in a metal, it is also possible to electroplate objects created in non-metallic sculptural media, including plaster. This can be done by first warming the plaster to ensure all residual moisture is driven off, before soaking the piece in linseed oil for a period of at least thirty minutes. After draining, the oil impregnated plaster is oven dried at a kiln temperature of about 70°C. Following this impregnating and drying process, the plaster should be effectively coated with a toughened oily skin, with no area of untreated plaster in evidence (to ensure full coverage, the oiling/oven process may be repeated on a number of occasions). Just before it’s attachment to the anodic terminal and immersion within an electroplate bath, the plaster is coated with a fine graphite powder, this conductive coating should enable the plaster to take on a satisfactory electrodeposit.
ELECTROPOLISHING >
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