What is varnish?
Varnish is a glossy coating that is applied as a liquid and dries to a hard clear or semitransparent film. Varnishes provide decorative and protective coatings for a wide variety of surfaces. They are used extensively on wood because they do not obscure the grain. They are also used to line metal food containers, to make paper resistant to moisture, and to insulate wire and cable. Oleoresinous varnishes are mixtures of resinous materials and drying oils, such as linseed oil and tung oil. These varnishes are usually made by heating the oil and resin mixture to temperatures ranging from about 450° F. to 600° F. (280° C. to 400° C.). The mixture is then cooled and thinned with a solvent, such as turpentine or petroleum naphtha. Oleoresinous varnishes dry by evaporation of the solvent, by oxidation, or by polymerization, a chemical reaction in the drying oil. Driers consisting of compounds of lead, manganese, and cobalt are usually added to speed the drying and hardening process. The resin
Varnish is a finish which can be applied to wood and other surfaces to create a hard, glossy film which will resist the elements. This type of finish is used in a wide range of situations, and it is a very popular method of finishing for floors, boat trim, and some cabinetry. Many home supply and hardware stores stock an array of varnishes for people to choose from, ranging from high-rated marine varnish which will last for years to more delicate furniture finishing varnishes. The goal of varnishing is to protect the underlying surface from damage. The finish will resist scratches, water, ultraviolet radiation, spills, chemicals, and many other hazards. Over time, the varnish itself may discolor, flake, peel, or crack, but the underlying surface will be perfectly safe. Eventually, it may become necessary to strip the finish, sand the surface to condition it, and then reapply a new layer. People have been using varnish since the days of the Ancient Greeks; the term “varnish” comes from
“Varnish is a thin, insoluble film deposit that occurs on the interior of lubricant systems and on components,” said Glen Sharkowicz, industrial lubricant specialist for ExxonMobil. “It’s usually sticky and difficult to remove by simply wiping it off.” Varnish is composed of lubricant degradation byproducts that range in color from light yellow to dark brown, he said. The byproducts are high-molecular-weight substances that are unstable in the lubricant, making them insoluble. “The chemical compositions of these insoluble materials vary from case to case with differences in additive technologies, outside stresses and contaminants affecting what are insoluble,” said Paul Sly, business solutions specialist, Isoclean Program for Chevron Products Company. “As these components that are normally dissolved in the oil become insoluble, they create soft, sub-micron particles that are polar and seek out other polar surfaces, like metal, to attach to.
