Surveys work completed and continuing on the physical and mechanical properties of artists’ materials. Test results of the individual materials show that fabrics can develop high tensile stresses at high humidity, whereas paint and hide glues lose strength. It is also shown that where low humidity can increase the stiffness and strength of hide glues and oil paints, it is really low temperature that causes true embrittlement of paint films. Oil paints can become brittle as a result of being exposed to elevated temperatures and cleaning solvents, and if left in a moderately benign environment they remain fairly flexible. The mechanical properties of oil paints continue to change over long periods, well after they are considered to be dry. The pigments used in making paint have a significant effect on both the drying time and the ultimate mechanical properties of the paint.