VARNISH

(Fr. vernis.) A fluid which when spread thin upon a solid surface becomes dry, and forms a coating, impervious to air and moisture. There are two kinds of varnish; namely, spirit a.nd oil varnishes: rectified alcohol is used for the former; and for the latter fixed and volatile oils, or mixtures of the two. The solid substances di olved in the above menstrua, and which constitute what is termed the body of the varnish, are almost exclusively resinous, and are chiefly the following: — 1. Turpentine, all the varieties of which are employed by the varnisher: they form an excellent body, and give strength and glo ine at a small expense; but they do not dry without other additions. 2. Copal, a peculiar resin, very dilBcult to di olve, but forming a hard and durable ingredient. It is generally melted over a gentle fire previous to use. 3. Lac, which gives great toughne and hardne ; but is often inadmi ible, on account of its reddish brown colour. 4. Mastic, which yields a tough, hard, brilliant, and colourle varnish. 5. Elemi, a resin of a pale yellow green tint, and a valuable ingredient, on account of its toughne and durability. 6. Sandarach, a resin which imparts splendour, but which alone is not durable. 7. Amber, a valuable ingredient, on account of its hardne and durability; but diflScult of transparent solution, and hence chiefly used in opaque varnishes. 8. Benzoin, added on account of its fragrancy. 9. Anime, which gives brilliancy and some scent. 10. Oamboge, for yellow varnishes. 11. D7-rt^o«'s Wood, for red Varnish. These, together with turmeric, saffron, and annotta, are chiefly used on account of their colour, and to cover bra and copper under the name of lacquers. 12. Caoutchouc. This extraordinary vegetable product has of late been much employed in a variety of preparations used as varnishes. It is invaluable where materials are to be rendered air-tight, as balloons, for example, and where at the same time flexibility, and even elasticity, are required; but its principal application in this way is in the manufacture of various water-proof articles. 13. Asphaltum, the varieties of which are indispensable in black oil varnishes. In making spirit varnishes, the strongest alcohol of commerce should be used (of a specific gravity not exceeding 820), and its solvent power over some of the more intractable resins is sometimes improved by the addition of a little camphor; in order to prevent the agglutination of the resin, it is often requisite to mix it 4N3 [s. 1298]