Process and technical characteristics of traditional gilding technology on silver: experimental replication and analysis of silver gilded products

Ancient fire gilding has been a longstanding traditional Chinese craft, utilizing the unique properties of gold and mercury through chemical methods to embellish a variety of objects with layers of gold. This technique, notably efficient compared to alternative gold decoration methods, showcases the adept utilization of precious resources, highlighting the advanced technological prowess of ancient China. The objective of this study is to replicate historical silver gilding technology within a controlled laboratory environment and conduct a comprehensive analysis of the resulting silver gilded products. Subsequently, a comparative analysis with research findings related to gilded cultural relics is undertaken to confirm and enhance the technological characteristics of the gilding process. The research findings indicate that the presence of residual mercury on the gold layer of gilded products is a consequence of employing gold-mercury alloys. Furthermore, the granular microstructure observed in the gold layer is a distinct outcome of the heating process, both representing typical technical features associated with traditional gilding techniques. Moreover, the Ag-Hg transition layer between the gold layer and the substrate results from the solid solution diffusion of atoms during the gilding process, serving as a unique process feature that securely bonds the two layers. Addressing the controversy surrounding heating temperatures, experimental findings indicate that exceptionally high temperatures are not necessary for the gilding process. The golden-yellow coating on gilded products is a blend of gold and various gold amalgam alloys, achievable through solid-phase transformation within the 122–419 ℃ range or solidification of gold amalgam after melting at temperatures exceeding 419 ℃. The phase composition of the gold layer provides crucial evidence for defining the appropriate heating temperature when exploring the formation mechanism of fire gilding.