Timber construction has gained a significant amount of momentum in the previous decades. Being a renewable material, the flexibility and adaptability of this material have allowed for a more environment-friendly construction.
In its crude form, wood is not fully usable. It undergoes cleaning and processing and finally, the finished product is what goes onto the structures. Finishes can be grouped into classes based on what they have to offer. There are varnishes, oils, waxes, and much more that are used as finishes on the wood.
Different finishes exhibit varying degrees of durability, protection, aesthetical appearance, and ease of application. Without a proper finish, the wood could crack, lose its natural appearance and tone, and deteriorate.
An appropriate finish prevents the wood from deteriorating and increases its natural life. Below is the list of the most used finishes on wood with their attributes and uses.
Oil finishes are highly popular with carpenters and woodworkers. They tend to highlight the original character of wood without altering its texture or color. Since oils are natural, they are easy to apply.
Linseed oil is primarily used as a finish for wood. Unrefined linseed oil is rarely used as a finish because it has a slow rate of drying. One of the best ways to use linseed oil as a finish is by boiling it, which results in a thick product that dries quickly. This product is known as polymerized oil or heat-treated oil.
Tung oil is available in an unrefined or polymerized form. The heat-treating process speeds up the drying time and makes the oil more efficient as a finish. It also reduces the tendency of tung oil to freeze. Tung oil exhibits better moisture resistance than linseed oil.
Varnishes create a transparent film-like layer on the surface, which covers the pores in the wood. It also highlights the natural characteristics of the wood.
Varnishes are made from synthetic resins that are modified with drying oils. These resins include urethane, alkyd, and phenolic. Other than linseed and tung oil, semi-drying oils such as soybean are also used.
Varnishes such as polyurethane are resistant to moisture and water. Some varnishes that protect the wood against ultraviolet rays are highly useful for outdoor structures such as gazebos and trellises. Residential architects suggest using this finish on wooden landscaping features.
Varnishes are regularly used on facades, frames, and internal parts. After some time when the varnish layer peels off, the wooden surface must be varnished again.
Waxes are a derivative of mineral, animal, and vegetable sources. These are marketed in a paste or liquid form. The most common are beeswax and carnauba.
As a finish, waxes do not penetrate the wood but form a protective layer. Many carpenters use wax as an additional finish along with oils or varnish to give the wooden surface a pleasing appearance.
Water-based finishes have the same ingredients as varnishes, particularly acrylic and urethane. However, some of the ingredients are replaced with water. Water-based finishes exhibit complex chemistry. Since resins do not have a natural affinity toward the water, they must be chemically modified to combine with it.
A water-based finish is usually made with an acrylic resin or urethane mixture. The addition of urethane toughens the resin and makes it scratch resistant.
Impregnants penetrate the wood, nourishing it from inside by allowing it to breathe. This gives off a more natural look. Since impregnants permeate the wood, it makes it water-resistant.
Impregnants are convenient to apply and maintain. However, they are not as protective as other finishes.
Shellac is a natural finish secreted by the insect Kerria lacca found in Thailand and India. The secretions are in the form of cocoons, which are gathered and refined into dry flakes. These flakes are then dissolved into ethyl alcohol, which results in the shellac solution.
Shellac is available in premixed or flake form that you can mix yourself with denatured (ethyl) alcohol. Shellac dries quickly and forms a strong film that is useful for varnishing wooden furniture and floors. At present, it is not used much as it is not highly resistant to water or alcohol.
Lacquer is regarded to be one of the best and most widely-used finishes for wood. It dries fast and imparts a richness to the wood and exhibits durability. Different types of lacquer exhibit different performance attributes.
The most common is nitrocellulose lacquer. It is a result of alkyd and nitrocellulose resin, which is mixed with solvents. Such a type of lacquer has moderate water resistance but is sensitive to heat. One of the preliminary disadvantages of this lacquer is that it yellows over time and that is visible in lightly-colored woods.
Acrylic-modified lacquer is made from a mixture of cellulose acetate butyrate and acrylic. This lacquer possesses the same properties as nitrocellulose lacquer except that it is water-white. This means that it will not show as an amber color when applied to light-colored woods. This lacquer does not yellow over time.
Another type is the catalyzed lacquer. It strengthens the relationship between the application of nitrocellulose lacquer and varnish. It is a finish comprised of urea melamine or urea-formaldehyde and an alkyd that has nitrocellulose resin added to it.
Adding the acid catalyst initiates a chemical reaction that results in a durable finish. Catalyzed lacquer is of two types namely pre-catalyzed and post-catalyzed. Pre-catalyzed lacquer has premixed components while post-catalyzed lacquer is to be devised using precise ratios at your home or workshop.
How to Understand the Durability of a Finish?
The durability of a finish is measured by its resistance to heat, water, chemicals, and scratches. Shellac, water-based finishes, and wax will be damaged if exposed to water long enough. Most of these finishes scratch easily, however, they rub out well.
Oil-based polyurethane is the most durable finish that can be applied by hand. Varnish and catalyzed lacquer are the most durable sprayed finishes.
It is essential to note that when considering wood finishes, several issues must be addressed. These include the possible use of the piece, where it will be installed, and its life expectancy. The crucial aspect is that the architect must be aware of the function of the wooden piece to find the most appropriate finish for the situation.
Whether you are transforming a wooden floor or just sanding your old wooden furniture, you must use the right type of finish to extend its life. Invest your time, money, and energy in a finish that will bear fruitful results.
Choose a finish that gives off a rustic yet modern look for your home that reflects through the furniture, doors, or even decorative wooden elements. So, let’s lookout for the best and most efficient finish out there.