Study of UV ageing effects in modern artists’ paints with MeV-SIMS

Abstract

In the present work, alkyd and acrylic self-made paints containing synthetic organic pigments (SOPs) of different chemical classes (phthalocyanine, quinacridone, and diketopyrrolo-pyrrole) were analysed by Secondary Ion Mass Spectrometry with MeV primary ions (MeV-SIMS) to study the chemical changes that occur due to accelerated UV ageing. MeV-SIMS is an emerging accelerator-based, surface-sensitive mass spectrometry technique that can provide information about the chemical composition in the uppermost layers of materials. Two-component mock-up samples were prepared and aged for two and four months, to mimic environmental ageing over periods of one and two years. The obtained results show that the studied SOPs are stable under the accelerated ageing conditions used in this study and that they can be easily identified in aged paints, while the binder components undergo structural changes due to the photodegradation processes. The kinetics of binder degradation were found to be dependant on the pigment present in the paint, with phthalocyanines having the highest photostabilizing effect amongst the pigments studied. In addition, the acrylic binder exhibited slightly higher stability to UV ageing than the alkyd medium. This study allowed the identification of SOPs and binders in the selected contemporary artworks, which date from different periods and belong to both outdoor and indoor collections.