Multi–analytical investigation of Eastern Han gilded copper coffin ornaments excavated from Wushan, Chongqing, China

Six Eastern Han Dynasty gilded copper coffin ornaments excavated from Wushan, Chongqing, were analysed by optical microscopy, SEM-EDS, and Raman spectroscopy. Results reveal all samples were gilded with mercury amalgam and gilded layer thicknesses ranged from 0.3 to 8.0 µm. Two distinct gilding techniques were identified: gold-mercury amalgam gilding and gold-silver amalgam gilding. The gold-silver technique was associated exclusively with tombs containing silver funerary objects. The substrates consisted of red copper, low-lead bronze, and leaded tin bronze. Seven corrosion products were characterized, including malachite, cuprite, atacamite, azurite, cerussite, brochantite, and libethenite. Corrosion behavior was closely linked to the integrity of the gold layer, with corrosion notably intensified in the vicinity of engraved surface marks.