Varnish, traditional finishing material in the wood finishing

Varnish is defined as a transparent, hard, and protective finish or film primarily used in wood finishes and other finishing. Based on this definition, the varnish has a very broad scope. All finishing materials that produce a transparent layer and protective film are included in the category of varnish. The modern clear coatings such as nitrocellulose, acid curing, PU, acrylic, and water-based can be named as the varnish, together with film-forming traditional finishing materials such as shellac and oil varnish.

It can be explained easily by looking at the history of finishing materials development in the past. In earlier times when the technology of finishing materials was still developing, the wood finishing materials that could display the beauty of wood grain and color were only the oil and wax finishes. But the oil and wax were not able to generate a layer of film that could give protection to its substrate underneath. While the other finishing that could provide better protection was the painted finish. A paint finish might give a better layer finish that can protect the substrate underneath but cannot produce a transparent appearance to show the beauty of the natural wood grain and color. Until the finishing industry found varnish, a material that is developed from the oil varnish finish. The varnish is a clear film layer that can make a transparent finish that can show the beauty of the natural base color and the grain of the wood. Since then, every finish with a transparent film is associated with varnish.

Varnish (oil varnish) is made from oil finish that is cooked and chemically processed with some additional material, resin, solvent, and other materials. The mixture composition of the varnish will determine the strength, quality, and character of the varnish. A varnish with a large percentage of oil is called a long oil varnish and will produce a more elastic and durable film finish. Meanwhile, the varnish with a low percentage of oil is called short oil varnish. This varnish will produce a tougher but less elastic film finish. Between the short-oil and long-oil varnishes, there is a medium-oil varnish whose general properties are between both.

Various kinds of varnish.
 
Varnish materials are available in many types and also various grades of quality. The higher the grade of varnish, the more transparent and more serviceable it is, but it is usually also more expensive. Varnish is also available in various types, each of which has its advantages and disadvantages. But, to do the proper selection, we need to know the types of varnish and the basic character of each. 

These are the following types of varnish, which are mostly used in wood finishing.

•  Spar varnish.

As the name implies, spar varnish was originally meant to be used as a material to coat the wood on the ship. Therefore, the varnish is designed to withstand the hot sunlight, cold nights, and rain in the extreme outdoor weather and even against salt water. Now spar varnish is also widely used to coat furniture or wood products that are used for outdoor purposes. Garden furniture, windows, or doors that are exposed to sunlight and outdoor weather are the items that are suited with this finish.
Spar varnish is a long oil varnish. It will form a film layer that is elastic, durable, and highly resistant to the outdoor weather, but it requires a long drying time.

• Floor varnish.

This is a medium oil varnish. It has a high strength and elasticity, although not as good as spar varnish. This material is designed for finishing the wood. It is strong enough to withstand the severe abrasion due to the foot and shoes and also strong enough to hold heavy objects like furniture that are placed thereon. This varnish also resists the moderate use of cleaning water. This material requires a relatively long drying time, but still less than the spar varnish. Although quite strong, this varnish will fade after the floor is used for some time, so a reapplication of this varnish is often needed.

•  Finishing varnish (furniture varnish)

This varnish refers to the varnish for furniture finishing. This is a short oil varnish. It is drying faster and tougher but less elastic. This varnish is hard enough to be rubbed to make a high-gloss finish. This varnish is more proper for finishing the indoor furniture. The use of this varnish is mostly in combination with other finishing material. The finishing process with varnish combined with stains, glaze, shellac, and other modern finishing materials is quite commonly found in the furniture finishing industry.