Study on degradation of Cambodian panel painting during UV aging

Abstract

AbstractIn this research, the glue films, ground and paint layers were aged under UV‐C radiation. The glue films were prepared using tamarind gum and liang‐chey resin powders. The ground (calcium carbonate mixed with tamarind glue) and paint layers (red cinnabar, malachite, Prussian blue mixed with liang‐chey resin) were applied on the iron wood using traditional tempera technique. The degree of disintegration was determined using scanning electron microscopy with energy dispersive X‐ray instrumentation, thermogravimetric analysis, attenuated total reflectance Fourier transformed infrared spectroscopy and powder X‐ray diffraction. The tamarind film turned brown after 14 days. While, liang‐chey resin film did not show any significant color change. The thermogravimetric analysis showed the lower thermal stability of the aged tamarind film. The discoloration and cracking on the ground layer surface stemmed from the disintegration of tamarind binder. After 14‐day exposure, the color of red cinnabar changed from bright red to dark red with black spots all over the surface. These spots were identified by powder X‐ray diffraction measurements as β‐HgS (black). After prolonged UV exposure, the white solid was appeared on the cinnabar surface and identified as anhydrite (anhydrous CaSO4) and gypsum (CaSO4.2H2O). The yellow color appeared on the malachite surface might come from the discoloration of the tamarind glue binder in the ground layer. While the brown layer found on aged Prussian blue surface was confirmed as the mixture of β‐PbO2, Pb3O4, and β‐FeOOH.