Varnish
2 of the 7 encyclopedias on this shelf carry an entry for Varnish. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
a thin, resinous fluid, which, when spread over the surface of wood, metal, glass, or other solid substances forms a shining coating, impervious to air and moisture. The great number of varnishes consist of some resinous material, dissolved in linseed oil, alcohol, or some liquid hydrocarbon such as turpentine and benzole. Those made by dissolving a resin in a nonvolatile drying oil, like that from linseed, are called oil varnishes; and those prepared by using volatile solvents (alcohol, benzole, etc.) for the resins are called spirit varnishes. In the case of the latter the solvent becomes dissipated as the varnish dries, so that when any surface is coated with a varnish of this kind only a film or coating of resin remains, which is apt to crack and peel off; but means are taken either in the preparation of the varnish or in the laying of it on to counteract this tendency. With an oil varnish, on the contrary, the oil remains as part of the coating, giving it toughness, while the resin gives it hardness.
Aiton's Encyclopedia (1910)
var'nish, a preparation used by painters and gilders in coating surfaces. A varnish differs from a paint in that the opaque white lead of the latter is replaced by a transparent gum or resin. The principal resins used for varnishes are lac, benzoin, copal, amber, asphalt, and mastic. When these resins are dissolved in heavy oils, they form a durable, hard, transparent coating capable of resisting the weather. Less durable varnish, used often for inside finish or for varnishing paintings, is made by dissolving a resin in oil of turpentine. The turpentine evaporates quickly, leaving the resin behind in a thin, transparent coat. Alcohol varnishes dry even more quickly than those made with turpentine, but they are less durable. See Lac ; Linseed ; Paint ; Painting Vasco da Gama. See Gama ; Vasco Da