A new method for analysis of light-induced fading of historical artists' paints

Light-induced degradation of pigments in artworks poses a significant conservation challenge. Wavelength-dependent degradation of pigments was investigated by artificially aging paint samples with narrowband light in a micro-spot and assessing degradation through changes in the reflectance spectra of the sample following fading. A novel set-up using hyperspectral imaging (HSI) was developed. This allowed continuous reflectance measurements of the samples directly before and after fading along the HSI slit, recording spatially resolved spectral information. Reflectance monitoring at both the faded position and the surrounding area at the same time provides a quality control for the measurement and allows for evaluation of the degree of reversion in the reflectance following the removal of degrading light. This method proposes higher accuracy monitoring of reflectance change and has been applied here to assess a range of pigments, to start to understand their degradation.