Wavelength-dependent fading of artists' pigments

The effect of visible radiation of different wavelengths on the deterioration of several fugitive artists' pigments and dyed textiles has been assessed. For red and yellow pigments, damage decreases as the wavelength increases. The relationship between wavelength and colour change for blue pigments and for ISO blue wool standards nos. 1-3 is less straightforward: radiation in the blue region is not necessarily the most damaging for these colorants. The deterioration caused by particular wavelengths depends on the energy of the radiation and the spectral absorbance properties of the colorant. The implications of the results on the selection of light sources and the use of blue wool standards to assess damage to museum collections are discussed.