Material analysis of the wall paintings in Xialu Temple,Tibet Autonomous Region,China

This wall paintings technology study in Xialu Temple was carried out by in situ investigations and laboratory analysis. The techniques used to analyze pigments, ground/white preparations, and binding media were: optical microscopy carried out with visible reflected light and ultraviolet light; polarized light microscopy; micro-Raman spectroscopy; micro-Fourier transform infrared spectroscopy; and scanning electron microscopy. The characterization of pigments, including the discovery of two rare organic pigments, improves knowledge about traditional Tibetan paintings. The analysis of the binding media and different types of ground/white preparations (asbestos, kaolin, and illite) allowed us to identify different stratigraphic compositions. Our findings indicate that the study areas were painted during at least four different time periods.     

Characterization of Zinc Carboxylates in an Oil Paint Test Panel

ABSTRACT

Zinc (carboxylate) soaps, formed by reactions between zinc oxide (ZnO) and fatty acids in a drying oil, are known to cause deterioration in the paint layers of modern and contemporary oil paintings. This study investigates zinc carboxylates that developed in an oil painting test panel designed to mimic the aging and degradation encountered in actual works of art. Following accelerated and natural aging, protrusions were noted on the surface of the test panel. A large protrusion with erupted gel features was extracted from the test panel, mounted in top view, and then cut to reveal the sample's cross section. The gel features, which resulted from the unreacted oil binder's separation from the paint matrix, facilitated zinc carboxylate formation. Using reflectance µ-FTIR and SEM-EDX analysis, the morphologies and spatial distributions of zinc carboxylates within the gel regions of the protrusion were studied. A concentration gradient of zinc within the gel material was observed in the cross-sectional view, indicating patterns of zinc carboxylate formation and migration.