Varnish is a hard, transparent film or finish that is commonly used for wood finishing, but it can also be used for other materials. Traditionally, it is made up of drying oil, a resin, and a thinner or solvent or Diluents. Wooden surfaces, paintings, and various decorative objects are protected by varnishes. Once varnishes dry, its solvent evaporates, and the remaining constituents oxidize or polymerize to form a durable transparent film.
- Drying should be rapid.
- It should look uniform and pleasing.
- It should be durable and weather-resistant.
- After drying, it should form a hard film.
- On drying, it should not crack.
- The use of varnishes can protect various wooden surfaces from rain, dirt, and atmospheric influences.
- For woodwork, oil varnish, consisting of a solvent and a drying oil, is the preferred choice.
- Spirit varnish, which is primarily comprised of alcohol, forms a protective coating when evaporation occurs.
- In such a varnish, Linseed oil is used as solvent.
- In this varnishes, hard resins such as amber and copal are dissolved in linseed oil as a solvent.
- It dries slowly, but forms a durable surface.
- It is recommended for all external wood work, and for joinery and fittings.
- It contains soft resins, such as common resin, mastic gum, gammer, etc., dissolved in the best turpentine oil.
- In comparison with oil varnishes, It is less durable.
- It is light in color and also dries quickly.
- It is applied to painted surfaces.
- Soft resins such as lac or shellac are dissolved in methylated spirit of wine as the solvent.
- It dries Very quickly but not durable.
- French polish, Lacquer & Shellac etc are the example of Sprit varnish. French polish is made by dissolving the resin in sprit.
- It is commonly used on furniture and wooden surface.
- It is made by dissolving resin such as lac, shellac in hot water.
- It is used for varnishing wall papers, maps pictures,posters, book jackets etc.
- It is used on ship or boat in order to protect the timber from exposure to the elements.
- It is also known as marine varnish.
- Modified phenolic resin and tung oil are frequently used.
- It is not used for the external woodwork.
- Linseed oil is dissolved in melted asphalt to produce this type of varnish