The techniques of surface enrichment of jewelry and artefacts made from gold alloys, sometimes referred to as depletion gilding, have been known for over 2000 years. They were practiced by the early Egyptians and by the Pre-Columbian Indians of Central and South America. This presentation gives a brief historical introduction and reviews the archaeological evidence. Experimental work by the author and a co-worker in 1981 is described and related to the processes of wet and dry coloring and acid pickling used by the jewelry trade during this century. These surface enrichment processes appear to have been replaced by chemical 'bombing' using cyanide/peroxide solutions, a potentially dangerous operation. The problems of 'bombing' are discussed and suggestions for alternative safer processes given.

Author: Mark Grimwade