"A solution of resin in a volatile solvent that, brushed or sprayed on a surface, dries to a hard, glossy, and usually transparent film, which serves as a protective coating; also the coating itself." (Mayer) An effective varnish protects paint surfaces from dampness and atmospheric dirt without altering the coloration. It should also be easy to remove for cleaning or restoration. Some varnishes are made with colors, but these are recommended for industrial use only and not for artwork. Varnishes manufactured in the late 20th-century are considered by some professionals to be much more desirable for long-range use than previously-used varnishes that caused yellowing with age and dirt and led to crackling because of the oil paint being unable to "breathe". Sources: Ralph Mayer, "A Dictionary of Art Terms and Techniques"; Kimberley Reynolds and Richard Seddon, "Illustrated Dictionary of Art Terms". <br><br>Generally, a more or less transparent film-forming liquid that dries into a solid film.<br><br>Liquid applied as a coating for protection and appearance.<br><br>Resins in oil or solvent, used primarily for protecting the surface of the painting.<br><br>A protective transparent finish applied in a liquid state to a surface. One example is glair; a varnish for tempera paint. Many are available with a matte, semi-gloss, or glossy finish.Related link: The National Gallery of Canada has posted "before and after" pictures of a painting it restored by removing aged varnish. It had become hazy and brown. The restoration process revealed that Anthony van Dyck's Suffer Little Children to Come unto Me (c. 1618, oil on canvas, 131.4 x 198.2 cm) was a work in progress. Also see acrylic and oil paint, medium, pigment, polymer, polyurethane, resin, shellac, stain, stain removal, wood, and xylene.