Sensitivity of Modern Oil Paints to Solvents. Effects on Synthetic Organic Pigments

Abstract

Synthetic organic pigments are widely used in contemporary artists- and house paints. They can be found in artworks since 1900. Because of their special particle properties and their solubility in solvents, however, synthetic organic pigments pose a special challenge in conservation treatments. Analyses have been carried out on 23 synthetic organic pigments in oil paint films with six representative solvents. Solubility of the pigments upon solvent exposure has been determined by UV-Vis-spectroscopy. Some pigments have shown high solubility and were even extracted out of the oil paint film. Detailed examination on the influence of pigment extractions from the oil paint film was carried out with light microscopy, Raman- and ATR-FTIR spectroscopy. Swab tests elucidated that all pigments are very sensitive to the combination of (mostly) polar solvents and mechanical stress. The study demonstrates that mechanically applying solvents to paint surfaces containing synthetic organic pigments is delicate due to (a) the solubility of the pigments themselves, (b) mechanical removal of pigment particles – likely supported by the temporary destabilization of the binder. These findings have important implications to conservation practice.