Microstructural and Componential Characterization of the Plating Technology on Chinese Han Dynasty Bronze Fragments

Abstract

The bronze wares of the Han Dynasty excavated in Chongqing are decorated with plating patterns, maintaining an exquisite lustre right up to modern times after the covering patina is cleared away. In this paper, a plated fragment of the Han Dynasty from the Wushan County Museum was characterized by combining optical microscopy (OM), scanning electron microscopy with X‐ray energy‐dispersive spectrometry (SEM–EDS), X‐ray fluorescence analysis (XRF), X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS). The results showed that the bronze fragment was gilded with a ~ 3 μm thick gilded layer and a ~ 20 μm thick silvered layer. The high concentration of Hg and Hg‐rich intermetallic compounds confirmed the existence of mercury gilding/silvering technology, for example, Au9Hg in the gilded layer and Ag13Hg7 in the silvered layer. An ordered stripe structure was observed in the gilded surface, corresponding to the formation of rod‐like, intermetallic Au–Hg compounds. Specifically, a high concentration of Au was detected in the silvered layer. The exploration of gilded/silvered bronze casts light on this ancient technology and the benefit of identifying, protecting and reproducing it.