N. Herascu, M. Simileanu, Color changes in the artwork materials aged by UV radiation, Romanian Reports in Physics , 60/1 (2008) 95-103

Title: Color changes in the artwork materials aged by UV radiation

Abstract: Color is the main essence of most artworks: paintings, stained-glass windows, miniatures, statues, monuments, historical textile. Because some constituents of artwork materials are sensitive to UV light the color change will be occurs. Consequently, it directly affects the appearances of the art objects. The changes in art objects color caused by ageing of artwork materials are major problems encountered by artists, conservators and museum curators. Thus, for conservation and restoration purposes it is important to monitor color changes induced by the natural ageing and cleaning procedures using UV radiation. Thus, the goal of our study was to evaluate the effects of direct UV exposure of certain artwork materials using color spectroscopy. The samples were artificially aged under the UV light (254 nm) under constant environmental and room conditions (temperature -22 degrees C and relative humidity -55% RH). Prior and after artificial UV ageing, the reflectance spectra of all samples were acquired using a JASCO V-550 spectrophotometer. To quantify the color changes that may occur because of UV exposure the colorimetric parameters were determined using the CIE L*a*b* procedure. Thus, it has been shown that accelerated and artificial UV ageing with 254 nm lamp yields to different (photochemical) effects show by color appearance changes such as strong discoloration of the organic artwork materials comparing with those of the UV laser irradiation used in the cleaning procedure.

Key words: UV radiation; organic material ageing; color changes; CIE L*a*b*