Microscale mechanochemical characterization of drying oil films by in situ correlative Brillouin and Raman spectroscopy.

Correlative Brillouin and Raman microspectroscopy (BRaMS) is applied for the in situ monitoring of the chemical and physical changes of linseed oil during polymerization. The viscoelastic properties of the drying oil throughout the phase transition were determined by Brillouin light scattering (BLS) and joined to the Raman spectroscopic information about the chemical process responsible for the oil hardening. A comparative study was then performed on an oil mock-up containing ZnO, one of the most common white pigments used in cultural heritage. The intriguing outcomes open new research perspectives for a deeper comprehension of the processes leading to the conversion of a fluid binder into a dry adhering film. The description of both chemical and structural properties of the polymeric network and their evolution are the basis for a better understanding of oil painting degradation. Last, as a feasibility test, BRaMS was applied to study a precious microfragment from J. Pollock's masterpiece