The Swelling of Artists' Paints in Organic Solvents. Part 1, a Simple Method for Measuring the In-Plane Swelling of Unsupported Paint Films

A simple method is presented for measuring the in-plane swelling of paint films when immersed in solvents. The method is a development of a low-power microscopy approach first described in the 1960s, with improvements to the measurement aspect through the use of computer-based digital image analysis. Small fragments of paint (2–5 mm2) from stock films of uniform thickness are immersed in the test solvent, and images of the samples are captured electronically at intervals from t = 0 until equilibrium swelling is reached. Image analysis software is used to measure change in the areas of the fragments over time, resulting in swelling curves of time vs. % change in area. The experimental method is described in detail, together with a discussion of key factors relevant to uncertainty in the results. The swelling behavior of various paint films in ethanol and in some other common solvents is described.