Definition:
(noun)
In its simplest form, oil paint is a mixture of three things: pigment, binder and thinner. Pigment is the colour element, while the binder (the oil) is the liquid vehicle or carrier which holds the ground-up pigment to be applied to the canvas or whatever support is to be painted.
A thinner is usually added to the viscous pigment-oil mixture to make it easier to apply with a brush. Thus for example, one of the simplest oil paints might contain a mixture of red iron oxide (the pigment), linseed oil (the binder) and turpentine (the thinner). Oil paint may also contain a number of other additives, to promote drying, appearance and other actions.
What Sort of Oil is Used in Oil Paint?
Unlike tempera, acrylic paint, watercolour, or gouache, all of which dry by evaporation, oil paint dries by oxidation - meaning, the oil reacts chemically with oxygen in the air and gradually changes from a liquid to a gel and finally becomes hard.
What Types of Oils are Used in Oil Paint?
The most popular type of oil used in oil painting is linseed oil because (unlike other vegetable oils like olive or canola oil) it dries by oxidation. Linseed oil is not the only drying (or siccative) oil: safflower, poppy seed, or walnut oil may also be used, depending on the sheen, drying time and other effects required by the painter. However, linseed oil tends to dry faster and, in the process, forms a more flexible paint film that can be reworked more easily. Note also, that pigments do not dry at the same speed: charcoal black oil paint, for instance, tends to be slower to dry while red/yellow ochre hardens much faster.