Organic solvents are often used to assist in the removal of varnishes and overpaints, however their effect on the properties of paint films has not yet been well established. The effects of organic solvents on the mechanical properties of alkyd and oil paint are here examined. Alkyd paints were very popular in the 1950s, when artists like Jackson Pollock stated: “New needs need new techniques”. The solvent response of household paints based on oil-modified polyester resin is compared with that of artists’ alkyd paints and oil paints. Swell tests on paint strips suggest that all paint systems respond to the same solvents, but alkyd paints are less sensitive. Leached components were characterised by FTIR. As expected, more polar solvents tend to extract more polar paint components. To detect the changes in the mechanical properties, stress-strain measurements were performed before and after solvent treatment of the different pigmented paint strips. These clearly show that alkyd and oil paints become more stiff and brittle due to treatment with different solvents. Although the extraction of polar and softening components has an influence on the mechanical properties of paint films, as widely reported, the results shown here demonstrate that it does not seem to be the only factor responsible for the mechanical changes. The swelling power of solvents and the extraction of low molecular components are just two factors. Other properties like evaporation rate have an important influence on the solvent-induced degradation of alkyd and oil paint films. Moreover, our results suggest a more complex degradation mechanism of the paint film when exposed to solvents, not simply explained by the extraction or swelling phenomena. The results reported here will help the conservator to estimate the potential harm of organic solvent-based conservation treatments like the removal of varnishes or overpaints.