What is oil on canvas?

Oil paint is a slow-drying type of paint made from pigment particles suspended in a drying oil, typically linseed oil. The viscosity of the paint can be adjusted by adding a solvent like turpentine, and varnish can be added to increase the glossiness of the dried paint film. Oil painting has been used since the 12th century in Europe, initially for decoration, but it was not widely adopted as a primary painting medium until the 15th century.