Traditional oil painting techniques often begin with the artist sketching the subject onto the canvas with charcoal or thinned paint. Oil paint is usually mixed with linseed oil, artist grade mineral spirits, or other solvents to make the paint thinner, faster or slower-drying. (Because these solvents thin the oil in the paint, they can also be used to clean paint brushes.) A basic rule of oil paint application is 'fat over lean', meaning that each additional layer of paint should contain more oil than the layer below to allow proper drying. If each additional layer contains less oil, the final painting will crack and peel. This rule does not ensure permanence; it is the quality and type of oil that leads to a strong and stable paint film.
There are many other media that can be used with the oil, including cold wax, resins, and varnishes. These additional media can aid the painter in adjusting the translucency of the paint, the sheen of the paint, the density or 'body' of the paint, and the ability of the paint to hold or conceal the brushstroke. These aspects of the paint are closely related to the expressive capacity of oil paint.