Characterization of lacquer films from the middle and late Chinese warring states period 476-221BC

The famous lacquer wares excavated from the Jiuliandun Tombs of the middle and late Warring States period (476-221 BC) were analyzed using scanning electron microscopy/energy as well as dispersive X-ray spectrometry (SEM/EDS), Raman spectroscopy (RS), optical microscopy (OM), and X-ray diffraction (XRD). The results showed a multilayer structure in the lacquer film, including a Qihui layer (a layer made of lacquer and various plasters), undercoat layer (or finishing coat) and colored paint layer mixed with various inorganic particles, such as quartz (SiO₂ ) and hydroxyapatite [Ca₅ (PO₄ )₃ (OH)], as fillers in the Qihui layers or orpiment (As₂ S₃ ) and cinnabar (HgS), which were used as a yellow or red pigment, respectively. With the help of elemental mapping images, a double-layer structure of the lacquer plaster was observed, corresponding to a mixture of lacquer liquid and bone ash [Ca₅ (PO₄ )₃ (OH)], with large-diameter particles in the ground lacquer layer near the wooden body and small quartz (SiO₂ ) particles in upper lacquer layer. Specifically, quartz particles detected in the undercoat layer as fillers could be beneficial for improving the moshardness value, cost reduction and abrasive resistance of the lacquer film. In fact, the mixed method that used urushi and inorganic particles to form lacquer plaster was an important technological innovation and deeply influenced lacquering technologies worldwide. The results of this study will not only contribute to understanding the importance of lacquer skills in the Chinese Warring States but also provide information for cultural relic conservation as well as modern lacquer manufacturing for their protection and duplication.