Page 40 - Copper and Bronze in Art: Corrosion, Colorants, Getty Museum Conservation, By David Scott

produce copper duplicates of engravings on wood. The method of production was to take a cast
of the block in wax or in gutta-percha and then to coat the surface of the mold with graphite.
The prepared mold was then suspended in a bath of copper sulfate, and a wire was connected
to the mold and to a battery; in essence the technology has not really altered over the last one
hundred years. The encyclopedia entry continues:
[I]n the course of a few hours a sufficiently thick plate of copper is deposited. The copy on
removal from the mould, is strengthened by being backed with type-metal For rotary
printing machines the electrotypes are curved, set-up type is also sometimes copied thus
instead of being stereotyped, the electro-deposited copper being harder than the stereo
metal. Copper is sometimes thrown down as a thin coating upon plaster busts and statu­
ettes, thus giving them the appearance of solid metal. In Paris too, it is now common to give
a thin coat of electro-deposited copper to exposed iron-work such as gas-lamps, railings,
and fountains. The iron is first painted, then black-leaded, afterwards electro-coppered and
finally bronzed. Cast-iron cylinders used in calico-printing are also coated with copper by
a single-cell arrangement. {Encyclopaedia Britannica 1898: s.v. "electro-metallurgy")

A lithograph showing the kind of quaint Parisian lamppost that would have been coated
with copper is illustrated in Smith (1977). Ingenious solutions were developed to create elec­
trotype copies in the round with a continuous operation by making an underlying copper anode
in the shape of the final completed object. After half the copper had been coated into the mold,
the mold could be removed and the second mold positioned around the other half of the wire-
anode framework; a diagram of the process is shown in Roseleur (1872).
The electrodeposition of copper was a common feature of Victorian industrial processes.
Napier (1857) records the use of copper in the coating of glass or porcelain, cornice carvings,
cloth, flowers, and other small objects. Molds of ferns and leaves were obtained using gutta­
percha softened in boiling water, or wax might be used instead, and prepared for electrotyping
by deposition of a dilute solution of silver nitrate on the surface of the mold. Some of these cop­
per replicas could afterward be coated with gold or silver, or "bronzed" by application of a solu­
tion to corrode the surface and turn it green. A more unusual recipe called for cleaning the
object with caustic alkali, brushing some black lead over the surface, and then heating it on an
iron grate. The final treatment involved haematitic iron ore with an "unctuous" feel, which was
brushed over the surface to produce a fine brown patina.
A Greek cased bronze mirror in the collections of the J. Paul Getty Museum, shown in FIG­
URE 1.2, provides an amusing example of the use of electrotyping to improve the appearance of
an otherwise plain mirror case by the addition of a "bronze" relief protome of a Greek head. Sus­
picions were first aroused by the fact that the patina on the case, which is quite genuine, was
very different in appearance from the cuprite patina on the portrait (Podany and Scott 1997).
When the relief protome was removed and examined, it was found to be an electrotype, a fact

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