Oil paint was technically introduced and developed during the mid 18th century but it has been used in Europe since 12th for modest decorations. Later it has been used widely as an artistic medium on canvas. Oil paint is a slow-drying paint formed by mixing pigments with an oil commonly linseed oil. Since the oil is made to dry with hard film, the intensity of the colours are protected. They are opaque paints and its viscosity may be reduced by adding solvents like turpentine or white spirit. Solvents like varnish may also be added to give a lustrous effect to the painting.