Investigation of Ryukyu lacquerwares by pyrolysis-gas chromatography/mass spectrometry

Two pieces of lacquer obtained from Ryukyu lacquerwares produced in the 17-19th century in the Ryukyu Kingdom belonging to the Urasoe Art Museum were analyzed by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The results were compared with the standard of natural lacquer film to determine the identity of the lacquer species. Urushiol (MW = 320), 3-heptylcatechol (MW = 208), and 3-heptylphenol (MW = 192) were detected as pyrolysis products of lacquer pieces of a lacquer tray made by the hakue technique, suggesting that this Ryukyu lacquerware was coated with lacquer sap tapped from a Toxicodendron vernicifluum lacquer tree. On the other hand, urushiol (MW = 320), 3-heptylcatechol (MW = 208), 3-heptylphenol (MW = 192), laccol (MW = 348), 3-nonylcatechol (MW = 236), and 3-nonylphenol (MW = 220) were detected as pyrolysis products of lacquer pieces from a dinner tray made by the mitsuda-e technique, suggesting that this Ryukyu lacquerware was coated with mixture lacquer sap tapped from T. vernicifluum and Toxicodendron succedanea lacquer trees, respectively. Moreover, microscopy and cross-section studies demonstrated that the lacquers had a multi-layer structure. X-ray analytical microscopy was carried out directly on the surface of lacquerwares to determine the presence of different pigments.