New advances in understanding the curing, ageing, and photo-aging processes of blended Thitsiol/Urushiol Asian lacquers by THM-GC/MS and other techniques

Asian lacquer is a durable and beautiful coating material which has been used in Eastern Asia countries for thousands of years. Nowadays, numerous western museums host a large number of precious Asian lacquered objects, often made by using a blend of the less expensive thitsi-type lacquer and rushi-type one. In this work, for the first time, a blend of thitsi and urushi in three different percentage concentrations has been characterized and monitored during the curing, natural, and artificial ageing processes and a correlation with pure thitsi and urushi has been found. The using of physical and chemical techniques, such as Digital Microscopy in the first case and Fourier Transform Infrared Spectroscopy and Pyrolysis Gas Chromatography/Mass Spectrometry in the second one, allowed to describe the degradation process in all its aspects. This includes the formation of micro-cracks on the surface of the material strictly dependent on the formation of oxidation products in the chemical composition.