What is VARNISHES?

are solutiins of resinous substances which, w hen spread over the surface of any object, leave behind, after evaporation of the volatile vehicle, a thin shiny layer of the dissolved bodies. Varnishes are used as protective coverings to painted wooden, iron, and other surfaces. Copal, shellac, dammar, sandarach, mastic, elimi, benzoin, anime, resin, asphalt, etc., are all used in compounding them according to the purpose of their applications, copal varnish being one of the most important. To dissolve copal and some of the other gums, it is requisite to powder and subject them to a process of dry distillation at a temperature of about 360 degrees C., by which treatment they lose from 20 to 25 per cent, of their weight. They can then be dissolved in turpentine and boiled linseed oil. While these two liquids are used in compounding ordinary varnishes, others are made using spirits of wine, or petrol, or turpentine, or other solvent alone. Driers are chemical materials used in varnish and paint making to facilitate the drying process. For varnishmaking, manganese dioxide, manganese resinate, manganese borate, and litharge are used; while for paints, apart from the drying properties of any lead oxides that may be incorporated, and that of the varnish itself, the drying depends mainly upon the, boiled linseed oil used in compounding them.

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Definition of  VARNISHES