This short article describes solvent swelling, deswelling and leaching of linseed oil films. Changes in thickness of fixed films are measured with an apparatus similar to a parallel plate viscometer. Free film thicknesses were observed under a measuring microscope. Linseed oil films are random, amorphous structures, low molecular units diffuse into the solvent phase. Degree of swelling at equilibrium depends on the solvent. Results are analysed according to cohesive energy densities and solubility parameters. Degree of swelling plotted against solubility parameter gives a resonance curve. 9.3 units is the solubility parameter for films of dried linseed oil. Solvents close to this parameter have the greatest swelling action. Rates of swelling or diffusion can be estimated using Fick's Law of diffusion for a semi-infinite solid. A similar equation gives deswelling data for linseed oil films. Rate of diffusion of solvent increases with temperature and indicates a simple physical absorption of the solvent. Pigments slow the rate of diffusion. Solvents with low swelling and leaching capacity are best for the cleaning of paintings.