Abstract
Renaissance oil paintings represent pinnacle achievements of Western art, yet their long-term preservation is challenged by dynamic chemical degradation processes affecting both inorganic pigments and organic lipid binders. This study investigates the complex degradation mechanisms of characteristic Renaissance pigments—specifically smalt, verdigris, and vermilion—bound in aged linseed oil matrices using a complementary analytical approach coupling micro-Raman spectroscopy with Gas Chromatography-Mass Spectrometry (GC-MS). Historically accurate paint mock-ups were subjected to accelerated photo-thermal and relative humidity aging cycles alongside authentic micro-samples from sixteenth-century easel paintings. Micro-Raman spectroscopy elucidated structural transformations within the crystalline pigments, capturing the loss of tetrahedral cobalt coordination in smalt, the formation of basic copper carboxylates and oxalates in verdigris layers, and sub-surface chlorine-mediated alteration pathways of vermilion. Concurrently, GC-MS quantified lipidic binder oxidation through the evaluation of azelaic-to-palmitic (A/P) and palmitic-to-stearic (P/S) fatty acid methyl ester ratios, revealing that transition metal ions catalyze binder autoxidation and network scission. The integration of vibrational and chromatographic profiles offers unprecedented molecular insights into pigment-medium interphase phenomena, establishing a diagnostic framework that enhances conservation strategies and environmental microclimate controls for cultural heritage artifacts.
