What Is Varnish?
Varnish is a resin-based solution used on wooden surfaces to provide a transparent, hard, and protective film. Most varnishes are a blend of resin, driers, and solvents. The process of applying varnish on surfaces is known as varnishing.
Varnishing is done only on wooden surfaces. Varnish plays a vital role in finishing wooden surfaces of doors, windows, floors, furniture, etc. In this article, we will discuss different types of varnish used on wood.
Purpose And Advantages Of Varnish
i) It gives brilliance to the painted surface.
ii) It protects the surface against harmful atmospheric effects.
iii) It increases the durability of the paint coating.
iv) It makes the wooden surface beautiful without hiding the natural grains of the wood.
Requirements Of A Good Varnish
i) The varnish should not shrink or develop cracks after drying.
ii) The thin film of varnish should be hard and durable.
iii) The varnish should dry rapidly.
iv) It should make the surface glossy.
v) It should give the finished surface a uniform color and pleasing appearance.
vi) It should not hide the natural grains of the wood.
vii) The natural color of the varnish should not fade away when the finished surface is exposed to the atmosphere.
viii) The varnish should be long-lasting.
Types Of Varnish
Depending upon the solvent used, varnish can be of the following types:
- Oil varnish
- Spirit varnish
- Turpentine varnish
- Asphalt varnish
- Water varnish
- Flat varnish
- Spar varnish
- Oil varnish
1. Oil Varnish
These types of varnish are produced by dissolving hard resins such as amber and copal in linseed oil. Turpentine may also be used in small quantities to make the varnish thin and to render it workable. Oil varnishes dry slowly, forming a hard and durable film over the surface.
2. Spirit Varnish
This type of varnish is manufactured by dissolving resins such as shellac or lac in methylated spirit. Suitable pigment may be added to give the required shade to the varnished surface.
Spirit varnish dries very quickly and gets easily affected by the weathering action. It is mostly used for wooden furniture.
3. Turpentine Varnish
This type of varnish is prepared by dissolving gum dammer, mastic, and rosin-like resins in turpentine. These varnishes are light in color and also dry quickly. But turpentine varnishes are not as tough and hard as oil varnishes.
4. Asphalt Varnish
In this type of varnish, melted asphalt is dissolved in linseed oil. Sometimes a suitable amount of turpentine or petroleum spirit is added to make this varnish thin. Asphalt varnish is normally used for varnishing fabricated iron and steel products.
5. Water Varnish
This type of varnish is prepared by dissolving shellac in hot water. Shellac does not dissolve easily in water. To make it dissolve quickly ammonia or potash, soda, or borax are added to the water. These varnishes are used for painting pictures, posters, and maps.
6. Flat Varnish
It is an ordinary type of varnish. Materials like wax, finely divided silica, and metallic soaps are used in this varnish to reduce the glossy finish of the varnished surface. Usually, it gives the surface a dull appearance.
7. Spar Varnish
This type of varnish is mostly used on spars and other exposed parts of the ships. Flat varnish is very good weather resistant but not suitable for indoor use.
Process Of Varnishing
The process of varnishing wooden surfaces is as follows:
1. Preparation Of Surface
The surface is to be thoroughly rubbed smooth using sandpaper and cleaned of dust and dirt.
2. Knotting
All the knots should be covered with a hot preparation of read lead and glue size.
3. Stopping
After knotting, the wooded surface is stopped. This is done using hot weak glue size. This coat fills all the pores of the surface. 1 kg of glue normally forms about 10 liters of glue size.
If glue is not available, two coats of boiled linseed oil can be used as an alternative. After stopping when the surface becomes dry, it is rubbed again with sandpaper.
4. Applying Varnish
When the stopping process is done, it’s time to apply varnish to the surface in very thin coats. Fine haired varnishing brush should be used to apply varnish. When the first coat becomes dry, the second coat is to be applied.
So, that’s all about types of varnish and their application process. I hope you now have enough knowledge about it. If you have any questions, ask them in the comments.
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