Shuya Wei a,*, Valentina Pintus a,b, Václav Pitthard c, Manfred Schreiner a,b, Guoding Song d

a Institute of Natural Sciences and Technology in Arts, Academy of Fine Arts in Vienna, Austria
b Institute of Chemical Technologies and Analytics, Analytical Chemistry Division, Vienna University of Technology, Austria
c Conservation Science Department, Kunsthistorisches Museum, Vienna, Austria
d Department of Scientific History and Archaeometry, Graduate University, Chinese Academy of Science, Beijing, China

Abstract: This work presents the results of an investigation of the lacquer objects excavated from a Chu tomb in China (Warring States, 481e221 BC). This study is engaged in the examination of the methods and the materials used for the urushi coating on the objects. X-Ray fluorescence and Scanning Electron Microscopy/Energy Dispersive Using X-Ray (SEM/EDX) analyses were applied for the pigment identification. The results show that vermilion was for the red colour, while carbon black was for the black colour. Pyrolysis gas chromatography and mass spectrometry (Py-GC/MS) was applied for the characterization of the lacquer resulting that it is based on urushi. The possibility to classify the drying oil (tung or linseed oil) present in the lacquer is highlighted and discussed in this paper. Py-GC/MS with in-situ hydrolysis and methylation reagent tetramethylammonium hydroxide (TMAH) were performed on reference materials of linseed oil and tung oil as well as on the lacquer object samples. The results show that it is possible to unambiguously identify the drying oil, in our case, linseed oil was identified to retard the rate of hardening.

Keywords: Py-GC/MS  TMAH  Tung oil  Linseed oil  Lacquer  Urushi

Analytical characterization of lacquer objects excavated from a Chu tomb in China