This study describes the changes in the infrared spectra of paint as a result of aging. The focus is on the influence of pigments on the long-term changes in the oil binding medium. Several naturally aged paints made with different pigments were analysed using Fourier-transform infrared spectroscopy (FTIR). One of the most pronounced effects observed in the infrared spectra of aging paint is the shifting and broadening of the carbonyl band due to the formation of carboxylic acids. Another effect of pigments on the oil binding medium is the catalysis of the hydrolysis of triglycerides, as indicated by the decreasing intensity of the ester absorption. Finally, the nature of the pigment included has a profound effect on the CH stretch absorptions. From these results it is clear that pigments can significantly alter the infrared spectra of drying oil, and should therefore be identified beforehand to ensure the correct assessment of the infrared spectra in drying oil paint.