Oil painting basics: what the paint is and why it lasts
What oil paint is made of, how it dries and why painters have used it for centuries.
Most of the famous paintings on this site, from Van Gogh to Vermeer, were made with oil paint. It is worth knowing a little about the material, since many of the effects you see in the pictures come directly from how it behaves.
What oil paint is
Oil paint is a pigment mixed with a drying oil, most commonly linseed oil, which is pressed from flax seeds. The pigment gives the colour. The oil holds the pigment together and dries to form a tough film. Historically pigments came from minerals, plants and even insects, and some are still used today, although many modern pigments are synthetic.
Why it dries slowly
Oil paint does not dry by evaporation, as watercolour does. The oil reacts with oxygen in the air and slowly hardens. A thin layer can be touch dry in a few days, but a thick layer can take weeks or months, and the full cure takes years. This slowness is the main reason painters like it: they can blend colours on the canvas, correct mistakes and work over several sessions.
Fat over lean
Painters following traditional method use a rule called fat over lean. A lean layer has less oil in it, and a fat layer has more. Each layer should have at least as much oil as the layer under it, or the surface can crack as the lower layers move. You can see the effect of cracking, called craquelure, on many old paintings. Not all old cracking is bad technique. Canvas and paint age and move over centuries.
Thin and thick paint
Glazing means painting a thin, transparent layer over a dry layer, which gives depth and glow. Vermeer is often discussed for subtle layering of this kind. The opposite is impasto, thick paint that holds the mark of the brush. Van Gogh's brushwork in Wheat Field with Cypresses is a good example. Oil can do both, and many paintings use both.
Supports and tools
Oil paint needs a prepared surface, known as a support. Canvas is the most common, but panels, paper and metal have all been used. Canvas is usually sealed with a layer called a ground, since raw canvas would absorb the oil. Brushes come in many shapes. Painters also use palette knives to scrape and spread paint, and a medium to adjust how the paint flows.
Safety and cleaning
Some traditional solvents, such as turpentine, are harmful to breathe, and many painters now use odourless mineral spirits or work with oil only and wipe brushes with oil and a rag. Rags soaked with drying oils can heat up as they dry and have started fires, so they should be laid flat or kept in water in a closed metal container. Check the guidance of the manufacturers for the materials you choose.
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- American landscape painting of the 1800s
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Written with AI assistance and checked against museum records and standard references. Spotted a mistake? Tell us.