Mechanical and Moisture Sorption Properties of Commercial Artists’ Oil Paint by Dynamic Mechanical Thermal Analysis (DMA), Nanoindentation, and Dynamic Vapour Sorption (DVS)

This study examined the physical, mechanical properties of selected proprietary artists’ oil paints. Two instrumental methods were used to examine the mechanical properties of the chosen test paints: dynamic mechanical thermal analysis (DMA) and nanoindentation. DMA tests were done on the polyester-mounted samples using modu-lus/temperature scans in single cantilever bending mode. The method indicated appreciable differences in glass transition temperature (Tg) within each sample set. Carried out under controlled temperature and relative humidity conditions, the nanoindentation testing included de-termination of modulus values, before and after 24 hour immersion in aliphatic hydrocarbon solvent, of the exposed and underside surfaces of yellow ochre and cadmium yellow paint samples from which the polyester could be removed. The ultramarine oil paint sample was tested by nanoindentation at different relative humidities in order to determine the extent to which the paint was softened by sorption of water. The degree of water uptake of the test paints in relation to rela-tive humidity was measured by Dynamic Vapour Sorption (DVS) which generated moisture sorption isotherms. The results showed sig-nificant increases in water uptake above 60% relative humidity.