Indexed on: 08 Feb '18Published on: 08 Feb '18Published in: Angewandte Chemie International Edition
The formation of metal soaps (metal complexes of saturated fatty acids) is a serious problem affecting the appearance and structural integrity of many oil paintings. We used tailored model systems for aged oil paint and time-dependent attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy to study the diffusion of palmitic acid and subsequent metal soap crystallization. The simultaneous presence of free saturated fatty acids and polymer-bound metal carboxylates leads to rapid metal soap crystallization, following a complex mechanism that involves both acid and metal diffusion. Solvent flow, water and pigments all enhance metal soap crystallization in our model systems. These results contribute to the development of paint cleaning strategies, a better understanding of oil paint degradation and highlight the potential of time-dependent ATR-FTIR spectroscopy for studying dynamic processes in polymer films.