Varnish is a clear transparent hard protective finish or film. It is neither a paint nor stain. In its native state it has little or no color, but may be pigmented as desired, and is sold commercially in various shades.
Varnish is primarily used to seal wood finishes where, stained or not, the distinctive tones and grains in the wood are intended to be visible. Varnish finishes are naturally glossy, but satin or semi-gloss sheens are available.
The term "varnish" refers to the finished appearance of the product. It is not a term for any single or specific chemical composition or formula. There are many different compositions that achieve a varnish effect when applied. A distinction between spirit-drying (and generally removable) "lacquers" and chemical-cure "varnishes" (generally thermosets containing "drying" oils) is common, but varnish is a broad term historically and the distinction is not strict.
Most resin or "gum" varnishes consist of a natural, plant- or insect-derived substance dissolved in a solvent, called spirit varnish or solvent varnish. The solvent may be alcohol, turpentine, or petroleum-based. Some resins are soluble in both alcohol and turpentine. The resins include amber, dammar, copal, rosin, sandarac, elemi, benzoin, mastic, balsam, shellac, and a multitude of lacquers.
