Characterization and localization of the oil-binding medium in paint cross-sections using imaging secondary ion mass spectrometry

Saturated monocarboxylic fatty acids (namely palmitic acid and stearic acid, which are markers for the type of oil used in paintings) can be identified with imaging secondary ion mass spectrometry (SIMS), while retaining spatial information. The P:S ratios presented were determined with negative ion SIMS in individual layers of paint cross-sections from 15th to 19th century paintings. The positive ion mass spectrum gives information about the speciation of the fatty acids (free, ester-bound or metal carboxylates), indicative of the drying stage of the oil. Studies on freshly applied multi-layered oil paint systems suggest the diffusion of oil triglycerides between layers, which will influence