Depletion Gilding: An Ancient Method for Surface Enrichment of Gold Alloys

Abstract

Ancient objects made of noble metal alloys, that is, gold with copper and/or silver, can show the phenomenon of surface enrichment. This phenomenon is regarding the composition of the surface, which has a percentage of gold higher than that of the bulk. This enrichment is obtained by a depletion of the other elements of the alloy, which are, in some manner, removed. This depletion gilding process was used by pre-Columbian populations for their 'tumbaga', a gold-copper alloy, to give it the luster of gold.

Keywords: Gilding, Depletion Gilding, Gold-Copper Alloys, Tumbaga, Gold-Silver-Copper Alloys, Electrum, Archaeological Artefacts, Gold-Copper nanoparticles, Nanoporous Gold