In Search of Durability, Part 2: Early Twentieth-century Perception of Lightfastness: Talens Artists Oil Paint

This article is the last of two articles on early twentieth century lightfastness assessment, focusing on the methodology employed by the Dutch paint manufacturer Royal Talens to evaluate the photostability of oil paints containing synthetic organic pigments (SOPs). The aim of this study was to support the conservation of modern artworks containing SOPs by leveraging resources from the period in which the paints were manufactured. The approach combined paint analyses with microfading tests on Talens’ historic oil paint samples to improve the knowledge of historic SOPs stability to light. Thirteen different SOPs contained in 21 historic paint outs were analysed in oil paint samples taken from six historical Talens colour charts (1918–1950). These SOPs belong to various groups, including monoazo, phthalocyanine, and triarylcarbonium pigments. To contextualise Talens’ practices, comprehensive art technological source research was conducted on the historical development of lightfastness assessments for SOPs in artists’ materials. Interestingly, significant discrepancies were found between the microfading results from Talens’ paint samples and Talens’ classification of lightfastness. Nevertheless, the method used for interpreting the micro fading measurements proved viable for qualitatively assessing SOP colour changes, potentially offering indications for the conservation of modern artworks containing SOPs.