A thinner is a volatile solvent or solvent mixture used to dilute (i.e. reduce the viscosity) of paints and varnishes (coatings) up to a viscosity suitable for application (coating, spraying, immersion) on a surface. When applied or drying, the thinner evaporates together with the solvents originally contained in paints and varnishes. Thinners are also used to wash surfaces before varnishing, and to wash equipment and accessories. Most commonly used are so-called oil paints or alkyd thinners for alkyd paints and varnishes, nitro thinner for cellulose nitrate-based paints (nitrocellulose), and water for water-soluble and dispersion paints and varnishes.