Degradation of Vermilion Red Color in Oil and Mural Paintings: A Comparative Applied Study

Abstract

The present study investigates and compares the vermilion red color change phenomenon in an oil painting executed on wood from the 18 th century stored at the Archaeological Museum Store of Manial Palace Museum, Cairo and a mural painting executed using Tempera from the Greco-Roman Periodin a destroyed archeological house next to Medinet Madi Temple, (35kms far from Fayoum city). The vermillion red color may change to dark red, brown, or grayish-white due to the exposure to the environmental conditions and pollutants, the common role of both light and chlorine as the main factors of red discoloration, some impurities in color components, as well as the dissolved salts and organic media used in painting. The blackness of the color was detected after doing an analytical study to identify the damaged products of the vermillion red using different methods of analysis (i.e. microscopy, X-ray diffraction, Energy Dispersive X-rays and Infrared). The change to gray color in oil paintings due to the presence of the prokovite was associated with cinnabar. In the mural painting, it resulted from the conversion to black hypercinnabar, not to the resin.