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 may 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.
Traditionally, paint was transferred to the painting surface using
paintbrushes, but there are other methods, including using
palette knives and rags. Oil paint remains wet longer than many other types of artists' materials, enabling the artist to change the color, texture or form of the figure. At times, the painter might even remove an entire layer of paint and begin anew. This can be done with a rag and some
turpentine for a time while the paint is wet, but after a while the hardened layer must be scraped. Oil paint dries by
evaporation, and is usually dry to the touch within a span of two weeks (some colors dry within days). It is generally dry enough to be
varnished in six months to a year.