This paper concerns the sensitivity of artists’ oil paints to organic solvents. Specifically, it examines the respective capacities of single organic solvents and mixtures of solvents to cause swelling as a consequence of sorption into the paint and solvency action thereupon. The swelling power of a solvent is essentially an indicator of its relative strength in terms of action on the original (oil) paint material. The paper collates and interprets the large body of experimental data that has been gathered on the solvent-induced swelling of two particular reference oil paint samples. These samples comprise uniform films prepared from mixtures of proprietary yellow ochre and flake white tube paints, one portion being artificially aged by exposure to high-intensity daylight and the other portion not light aged. The method adopted for measuring swelling employed a combination of low-power stereomicroscopy and quantitative image analysis. The initial output from the swelling experiments is a series of swelling curves for each solvent that shows the mean percentage change over time in area ?A % for the group of paint fragments of the particular sample type tested. Various approaches are explored to correlate the respective swelling powers of individual solvents with a range of solvency descriptors and physicochemical constants.