Microfading som verktyg för att förutse färgförändring av akvarell

Abstract

This study examines microfading as a tool to predict light induced colour change of water colour paintings. Microfading allows direct measurements of the material. By exposing a small area (0,2-0,4 mm) to very intense light while simultaneously measure the colour of the area with a spectrometer, a quick determination of the materials lightfastness can be made. Measurements have been executed on Carl Larssons ‘Lisbeth’, 1894 in the collection of Gothenburg museum of art. Further, measurements have been made on samples of indigo in gum arabic on gelatine-sized paper in order to evaluate the impact of spectral distribution of the light source used, the impact of the colour strength of the samples, the impact of angular distribution of the light source and whether reciprocity holds. These factors affect the accuracy of the test. Having them in mind, an estimation of the fading behaviour of the water colour painting can be made. The measured spots on the painting showed a low tendency to light induced colour change, below Blue Wool 3. The most sensitive spots where to be found in the red midtones. Microfading offers data which can be used together with a lighting policy to limit the degree of light damage to paintings on display.