Varnishes

Definition: A transparent solution of resinous substance in linseed oil, turpentine or in alcohol is called varnish.

Varnish on wood stairs

Characteristics of a good varnish: It should dry rapidly. It should form a hard film on drying. It should not crack on drying. It should be durable and weather resistant. It should give uniform and pleasing appearance. It should not hide the natural grains of the inner surface of timber.

Types of varnish Oil varnishes Turpentine varnishes Spirit varnishes Water varnishes

Oil varnishes: The varnishes in which linseed oil is used as solvent are known as oil varnishes. This varnish consists of hard resin like copal and amber dissolved in boiled linseed oil. These varnishes dry slowly and form a hard and durable film over the surface. Uses: they are generally used for exposed works.

Turpentine varnishes: These varnishes consist of soft resins like common resin, mastic gum, gammer, etc., dissolved in the best turpentine oil. These varnishes are light in color and dry quickly. They are not durable as oil varnishes. Uses: These varnishes are used on painted surface.

Spirit varnishes: These varnishes consist of soft resin like lac (or) shellac dissolved in methylated spirit. These varnishes dry quickly. They are not durable easily affected by weathering actions. Uses: There varnishes are mostly used for furniture and unpainted wood surfaces.

Water varnishes: These varnishes consist of soft resin like shellac dissolved in hot water by adding ammonia, borax or soda. Uses: These varnishes are used for maps, pictures, etc.,

The End … Thank you … Department of Civil Engineering, M.S.P.V.L Polytechnic College , Pavoorchatram. www.ustudy.in