Materials and provenance determination of lacquerware from the Ryukyu Kingdom period by pyrolysis-gas chromatography/mass spectrometry and 87Sr/86Sr isotope ratio

Abstract

Three wood chips found in a wooden coffin discovered in the Mumujyana graves of the Ryukyu Kingdom period were analyzed by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), and the 87Sr/86Sr isotope ratio of one piece was measured by multi-collector inductively coupled plasma mass spectrometry to determine the materials used to produce the lacquerware and their provenance. Results from the derivative Py-GC/MS indicate that the lacquer was produced from sap of both Toxicodendron vernicifluum, which grows in eastern Asia, and Toxicodendron succedaneum, which grows in southeastern Asia. The 87Sr/86Sr isotope ratios of the film layer and wooden base of one large chip, which is considered to be a stripped piece of the wooden coffin, were <0.710. The Sr concentration of the film layer, however, was 35.0 ppm, significantly higher than that of raw lacquer sap. It is possible that the Sr isotope ratios of the film layer reflect that of a black pigment observed by cross-section analysis. From the 87Sr/86Sr ratios of two parts of the chip, it is likely that the lacquer painting was done where the black pigment and wood were available. It is likely that the wooden coffin was constructed on the main islands of Japan. Meanwhile, the presence of a chip lacquered with Toxicodendron succedaneum demonstrates that the Ryukyu Kingdom had diverse trade relationships with surrounding countries.