The technique of red painting for bronze artefacts unearthed at Sanxingdui site, Sichuan, China

A large number of painted bronze artifacts were unearthed from the sacrificial pits at Sanxingdui, reflecting the outstanding bronze decorative techniques of ancient China. The material of red pigment, binding agent and decorative painting techniques used on Sanxingdui bronze artifacts are revealed by this paper. Specifically, red-painted samples were collected from a bronze ware with a tiger head and dragon body. Analysis by Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) showed that the painted decoration was created through a multi-layer coating process. Raman spectroscopy and SEM-EDS analysis confirmed that the material of red pigment is cinnabar. Analysis by Bicinchoninic Acid (BCA) and High-Performance Liquid Chromatography-Mass Spectrometry (LC-MS) confirmed that the binding agent was not animal glue. Furthermore, Infrared Spectroscopy (IR) and Gas Chromatography-Mass Spectrometry (GC-MS) analysis revealed that the red cinnabar pigment was bonded by lacquer. Based on the analytical data above, it can be inferred that the red in the grooves of sunken decors on Sanxingdui bronze wares was conducted by a multi-layer filling process. Firstly, lacquer was applied within the grooves, and then before it got fully solidified, a cinnabar layer was added for coloring. The cinnabar particles were gently pressed to secure them in the lacquer, with some particles embedding into the lacquer layer. The cinnabar and lacquer layers were applied alternately till the grooves were filled with red. The present study clarifies the filling process of red-painted decoration on Sanxingdui bronze wares, enhancing the understanding of the appearance of bronze civilization in ancient Shu as well as in Southern China.