Varnishes intensify the appearance of pigments on the painting surface by the refraction of light.
Although varnishes are traditionally clear, they can be toned or altered with the addition of pigments and other materials. Toned varnishes may be utilized to balance a painting whose appearance has changed with age. Varnishes are solutions of natural or synthetic resins in organic solvents that dry when spread thinly on a surface. The dried films are solid and relatively transparent. According to the composition of the solution, the films exhibit varying qualities of gloss, protective ability, flexibility, and durability.