Page 43 - Copper and Bronze in Art: Corrosion, Colorants, Getty Museum Conservation, By David Scott

twenty-three cut fragments allowed a digital image of the scroll to be created. Silicon rubber
molds were taken of each of the fragments, which had been flattened out so a copper electrotype
could be made. The original scroll was then reconstructed using this electrotype.
Some extremely important commissions were made in electrotypes, such as the "bronzes"
that adorn the Opera, Paris, and the 320 cm high statue of Prince Albert and four accompany­
ing figures, erected behind the Albert Hall in London as a memorial to the Great Exhibition
of 1851. The Prince Albert statue was electrotyped by Elkington & Company of Birmingham,
England, in 186I and has recently been restored. Many German sculptures were made by this
technique as well. Haber and Heimler (1994), who examined several nineteenth-century Ger­
man sculptures, were able to show that until the advent of World War I many of these were
made by electro typing. Two methods were used in production: first, electroplating copper onto
an isolated plaster core; and, second, electroforming of hollow objects in negative forms. Large
objects would be electrotyped in several pieces, which were then soft-soldered together, fol­
lowed by a recoating with copper to disguise the join. Extensive corrosion has been observed
especially on electrotyped statues that still retain their plaster cores and iron armatures.

Copper in early photography The use of copper sheets with galvanic coatings of silver was
an important part of the first practical photographic process,
named the daguerreotype process after Louis Jacques Mandé Daguerre (i789-i85i), who per­
fected it in 1833. The copper plates used were initially coated with silver by galvanic deposition,
which had recently become of commercial importance, followed by washing the plate in acid
to remove surface impurities and then carefully polishing it. The plate was then placed in an
enclosed box where it was subjected to iodine vapor. The sensitized plate was then exposed in
a special camera, with exposure times as long as thirty minutes, after which the plate was
enclosed in a second box and exposed to the fumes of heated mercury. The image now appeared
and was fixed in sodium thiosulfate and often toned in gold chloride. By the i840s, plates were
made commercially by silversmiths, who brazed a silver coating onto the copper, although indi­
vidual operators would often add galvanically deposited silver to the copper plate to improve the
smoothness of the product after polishing. The nature of the daguerreotype technique produced
an inverted, or mirror, image of the subject photographed.
A remarkable use of the principals of electrotyping was employed in taking a replica of the
surface of a daguerreotype to produce a new "photographic" image. The product, sometimes
known as a tinthotype, required great skill in order to produce a satisfactory result. One inter­
esting feature of the resulting tinthotype copy is that the image is inverted again, producing a
correction of the dageurreotype original.
According to Hill (i854), the first electrotyped copies were made by Armand-Hippolyte-
Louis Fizeau (i8i9-96). Hill states that before the experiment is attempted, the dageurreotype
must be free of all traces of sodium thiosulfate and perfectly fixed by gold chloride. The method

C H A P T E R O N E
26