Determination of Aging Parameters and Following Structure Changes in Red Oil Paints: A Comprehensive Study

Abstract

Oilpaintings occupy a prominent place in cultural heritage. However, inconvenient conservation conditions (humidity, heat, and light exposure) accelerate the aging of paintings, leading to the rapid deterioration of their originality and physical durability. In this study, the mock-up samples prepared on canvas with the ten highly preferred red oil paint types were artificially aged via UV ray exposure, and changes in paint structures were examined in detail. Before the UV accelerated aging process, prepared samples were kept in a drawer for one year without any treatment. Naturally aged samples were exposed to UV rays for 24 h, 240 h, and 720 h in the laboratory where the relative humidity (60 %) and temperature (35 °C) remained constant. The increased exposure time to UV radiation, temperature, and relative humidity caused dramatic changes in Vermilion Red, Azo Red Light, Alizarin Crimson-326, and Cadmium Red Orange mock-ups. Changes in the chemical structure of paints were characterized by Fourier transform infrared (FTIR) spectroscopy. Elemental composition and pigments of paints were characterized by scanning electron microscopy (SEM) with Energy Dispersive X-ray (EDX) and Raman spectroscopy, respectively. The morphological and textural differentiations were analyzed with the help of SEM in addition to stereo and optical microscopes. The CIEL*a*b* color values of the paints were detected via the spectrophotometric method. Microscopic images of the four paints with excessive CIEL*a*b* color measurements displayed significant cracks and splits, and the changes in their chemical structures were examined by FTIR. Degradation was observed in organic dyes containing azo and quinone groups, which absorb UV rays rapidly and are adversely affected by temperature, and in photosensitive inorganic paints Vermilion Red and Cadmium Red Orange. © 2025 Elsevier B.V.