In our examination of the painting Autumn landscape by Cuno Amiet (1906, oil on canvas), we have reported for the first time the formation of calcium soaps in a painting. The soaps were characterised by multiple analytical techniques, namely FTIR, CI-DTMS, and GCMS, and by 2D and 3D correlative microscopy combining light microscopy, SEM-EDX and SRXTM data. Based on all the data gathered we could propose a reaction path.
Synchrotron radiation x-ray microtomography (SRXTM) played a crucial role in this study. Information concerning the porosity of the ground layer, the location of early reactivity sites at the interface between the ground and the paint layers as well as the overall appearance of large protruding masses of white material were fundamental in the development and support of a hypothesis for the reactivity mechanism.