Varnish
Varnish is a finish applied to wood or other surfaces in order to provide a clear, hard, durable, protective finish. Varnish is usually a combination of a drying oil, a resin and a thinner or solvent. Varnish finishes are often, although not always, glossy. As opposed to paint, which contains pigment, and is opaque, varnish has little or no color, and is transparent.
There are many types of drying oils, both natural and synthetic, including linseed oil, tung oil, and walnut oil. Resins used in varnish include amber, copal, rosin, but today alkyd and polyurethane are most common. Traditionally, turpentine was used as the thinner or solvent, but has been replaced by white spirit or paint thinner.
For violin varnish, Walnut oil and linseed oil are most often used in combination with amber, copal, rosin or other resins. The oil is prepared by cooking or exposing to air and sunlight. The resin is "run" by cooking and reducing its weight and concentrating its color. The thickened oil and prepared resin are then cooked together and thinned with turpentine into a brushable solution.
After being applied, varnishes harden either by evaporation of a solvent, or by a chemical reaction. Oil varnish drying time depends on the ratios of oil to resin and turpentine and may be sped up by exposure to UV light.
Most natural varnishes consist of a gum or resin dissolved in a solvent. Depending on the solvent used, the three main types of natural varnish are spirit varnish (which uses alcohol as a solvent), turpentine varnish, and oil varnish. Spar varnish (also called marine varnish) is high quality waterproof and sunlight resistant varnish named for its use on the masts of ships (called spars).
The word lacquer refers to quick-drying, solvent-based, varnishes or paints. Lacquer is also a very durable, slow-hardening, varnish obtained from the sap of a varnish tree. Shellac uses alcohol as a solvent. Although not a particularly durable varnish, shellac is sometimes used as a primer or sealer for paint or varnish, or as a finish by itself
Synthetic varnishes include urethane or polyurethane varnish, varnishes that use water as a solvent, and epoxy varnishes.
See also
References
- Bob Flexner (1994). Understanding Wood Finishing: How to Select and Apply the Right Finish. Rodale Press 0-87596-566-0