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Published online by Cambridge University Press: 20 January 2017
Lothrop places on record the original study of the “mise en coleur” gilding of Coclé objects which Bergsøe had completed in 1940. The Coclé specimens were made of a copper-gold alloy with low gold content, and were cast in molds. Because such an alloy corrodes easily, the exact composition of the Coclé alloy could not be determined. The Coclé goldsmiths did not use the hammered overlay, mercury gilding, or leaf gilding processes, but rather the “mise en coleur” process in which the copper is removed from the surface of the alloy leaving a blackish-brown, spongy gold deposit as an overlay. This spongy overlay is compressed and returned to a golden color by hammering and burnishing. The surface copper was probably dissolved by ammonium carbonate derived from urine.