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Absorption Rates | Oils

Oil absorption rate is explained here in order to help you understand why the quantity of oil varies in different colours. The oil absorption rate describes the ratio of oil to pigment that is required to create a viable paint. A ‘fat paint’ has a higher ratio of oil to pigment and ‘lean paint’ has a lower ratio. Oil paint is made from pigment and a binder; the binder dictates the drying time of an oil paint, and some oils are slower to dry than others. The answer to the question of what makes for a high oil absorption rate lies in the shape and size of the pigment particles. Oil must completely cover the surface of pigment particles in order to bind the pigment, and the smaller the particle, the more oil is required. That leads to transparent colours such as Alizarin Crimson. Also, the more irregular the surface of a particle is, the more oil is required to cover the jagged surface. This explains why fat paint dries slower than lean and why the oil absorption rate varies from colour to colour.