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Woodwork Finishing

Wood finishing refers to the process of refining or protecting a wooden surface, especially in the production of furniture where typically it represents between 5 and 30% of manufacturing costs

Finishing is the final step of the manufacturing process that gives wood surfaces desirable characteristics, including enhanced appearance and increased resistance to moisture and other environmental agents. Finishing can also make wood easier to clean and keep it sanitized, sealing pores that can be breeding grounds for bacteria. Finishing can also influence other wood properties, for example tonal qualities of musical instruments and hardness of flooring. In addition, finishing provides a way of giving low-value woods the appearance of ones that are expensive and difficult to obtain.

Reasons for finishing wood

There are two reasons to apply a finish to your woodworking project: protection and appearance.

Protection. Wood is a porous material, capable of soaking in anything that gets on it, such as oils, dirt, and chemicals. A finish can seal the wood and keep “gunk” out of the grain. You’ve put a lot of time into your projects, so you’ll want to keep them looking good for years.

Appearance. All wood has a grain, some more vibrant than others. Finishes like stain will highlight and add some color to the grain, livening it up. Even clear coats add a sheen and warmth to wood that isn’t found when left raw.

Wood finishing procedure

Wood finishing starts with sanding either by hand, typically using a sanding block or power sander, scraping, or planning. Imperfections or nail holes on the surface may be filled using wood putty or pores may be filled using wood filler. Often, the wood’s color is changed by staining, bleaching, or any of a number of other techniques.

Once the wood surface is prepared and stained, the finish is applied. It usually consists of several coats of wax, shellac, drying oil, lacquer, varnish, or paint, and each coat is typically followed by sanding.

Finally, the surface may be polished or buffed using steel wool, pumice, rotten stone or other materials, depending on the shine desired. Often, a final coat of wax is applied over the finish to add a degree of protection.

French polishing is a finishing method of applying many thin coats of shellac using a rubbing pad, yielding a very fine glossy finish.

Ammonia fuming is a traditional process for darkening and enriching the color of white oak. Ammonia fumes react with the natural tannins in the wood and cause it to change colors. The resulting product is known as “fumed oak”.

Types of Finish

The level of protection and effect on appearance offered by a finish varies by the type you use, and there are many varieties to choose from. Some are used alone and some in conjunction with others. You don’t have to use all of them — just those that fit your needs and desires. There isn’t a “right” or “wrong” choice for your project; every woodworker comes to find a favorite finish after experimenting and figuring out their preferred look, application method, and desired effect for a piece.

Sanding

Sanding is carried out before finishing to remove defects from the wood surface that will affect the appearance and performance of finishes that are subsequently applied to the wood. These defects include cutter marks and burns, scratches and indentations, small glue spots and raised grain. Sanding should not be used to eliminate larger defects such as gouges, and various forms of discoloration.

Painting

Paint is a basic finish that covers and protects the material that it’s applied to. Paint isn’t usually used over natural wood, but it can be. If the paint coverage is thin, or semi-transparent, then the wood grain can show through, with dramatic effect. Paint is commonly used on woodworking projects made of MDF or plywood, as well as woodworking projects that require color.

Staining

Stain is used over natural woods or plywood so that the grain is visible and accentuated, while still adding some color — be it red, dark brown, light brown, etc. It can add some pop and warmth to a wood that might look a little boring otherwise.

Clear Coat

Wax. Wax is a simple finish to apply, as it’s simply rubbed on and buffed to a sheen. It works best on fine-grained woods that have been sanded to a smooth surface. It’s not best on rough-grained woods, such as oak or ash.

Waxing

Wax is not only applied to bare woods, but also on top of other finishes, such as shellac, to protect it from moisture.

Oils.

 Oils are an easy way to finish woodworking projects as they are simply applied heavily then wiped down to a dull sheen. They are quick to apply and can be re-coated over the years. Oils do not provide a shiny surface, though, and may feel sticky for some time.

Shellac. Shellac is an age-old finish that’s not used much these days. It is a resin that is dissolved in alcohol and then brushed on to projects. It’s not known for moisture protection, so it’s fallen out of favor over the years. Not the best choice for table tops, but can be used to add a natural amber-like warmth to your projects.

Varnishing

Varnish is similar to shellac, and also lacquer (see below). Varnish is usually wiped or sprayed on. More durable than shellac, varnish will stand up to moisture; one type is even used in wooden boat applications.