About this term
Source: Oxford University Press
Coating material consisting of resin dissolved in a liquid, which dries to form a transparent film. Drying may result from the evaporation of a Solvent vehicle to leave a glassy residue of resin, or from a combination of solvent evaporation and chemical reaction between resin molecules to form larger molecular units (polymerization). Traditionally, varnish films have a high gloss, but, by varying the varnish constituents and the method of application, it is possible to vary the degree of gloss as well as the hardness, toughness and flexibility of the film. Varnishes may be colourless or tinted by the addition of dyes or pigments. The word ‘varnish’ is derived from the medieval (c. 8th century) Latin veronix or vernix, itself related to the Greek berenice, then apparently used for amber. By extension, vernix came to be used for sandarac resin, sometimes confused with amber and a common ingredient in medieval varnish recipes. By the 15th or 16th centuries vernix also denoted juniper resin. The word ‘varnish’ only acquired its modern meaning around the late 16th century; before this time the liquid coating material was known by such names as the Italian vernice liquida.
From Grove Art Online