Finishing a piece of furniture is the most important phase of the fabrication process and takes a significant amount of time to complete. It requires judgment, craft, and human skill to determine how much color and/or finish to apply and to decide when the finishing process is complete. Final finishes needs to be carefully considered at the outset of any project because they can significantly affect cost and can influence the choice and quality of materials selected to fabricate the furniture.
Wood Finishing
There are many ways to finish wooden furniture. All finishes will darken wood by one to two shades. Water-based finishes such as polyacrylic finishes will retain the truest natural colors of light-color woods such as maple or birch sapwood. They are easy to apply with a brush but should be applied in the direction of the grain. The disadvantage to water-based finishes is that the water raises the grain, causing the wooden surface to become slightly rough, requiring sanding with 22-grit sandpaper. Waterborne finishes, when dry, are water resistant and referred to as water white clear.
Polyurethane finishes will darken the natural color of wood and cause it to turn amber. The first coat should be thinned for deeper penetration into the wood. Polyurethane finishes offer excellent protection against moisture. There will always be a cold joint between applications because polyurethane does not dissolve previously applied coats. Polyurethane is relatively easy to apply, and drying time is moderate.
Tung oil and Danish oil are considered "drying oils." They can produce beautiful hand – finished furniture, but they are labor intensive and require periodic maintenance.
Waterlox is a proprietary blend of resin, mineral spirits, and other ingredients "cooked" with tung oil to produce a durable and beautiful finish. It finishes well with a cloth application (diapers work best) and is easy to apply; drying time is moderate.
Shellac finishes are ideal for teak because shellac will bond well to the wood despite teak’s high oil content.
Steel wool and a good grade of furniture wax with carnauba will also produce a beautiful furniture finish, but it requires significant maintenance.
Precatalyzed and catalyzed lacquer finishes are the industry standard for wood furniture. Precatalyzed finishes produce a harder, more durable finish than regular nitrocellulose lacquers. Both are applied using a spray gun, and both can be touched up with a brush or spray (Figure 8.50). Applications of these finishes will dissolve the previous coats to produce a uniform finish. The thickness of these finishes is though limited to 0.005-inch or the cured surface may crack. Vertical surfaces generally receive two spray applications and horizontal surfaces no more than four applications. After 28 days, precatalyzed lacquers are nearly as resistant to moisture and chemicals as a polyurethane finish. These finishes will slightly amber the color of natural wood.
Plastic can be painted, sawn, drilled, sanded, or frosted. Plastic can also be buffed to remove tiny scratches.
Metals can be polished, brushed, and plated. Metals oxidize, but metal lacquer sprays can slow the oxidation process. Using a mild abrasive and special applicators, oxidized
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Figure 8.50 Spray finish using nitrocellulose lacquer. Photography by Jim Postell, 1994. |
metals can be polished to rejuvenate their original finish. Specific cleaners are available for most decorative metals.
As previously mentioned, stone slabs are delivered to a retailer polished on one side. Honed, finished stone is achieved with 200- or 400-grit stones, which will produce an even, finely textured, nonreflective surface. Flame, thermal, and hammer finishes are technically distinct, but they look similar on a rough, coarse surface. Stone finished in a flame, thermal, or hammer finish nearly always appears significantly lighter than it would in a polished state.
Glass is made either plate or tempered. The differences affect its strength and physical properties but not its appearance. Distressed glass has noticeable folds and a smooth but faceted surface. Glass can be chemically etched or blasted with sand. It can be sanded, drilled, beveled, seamed, and polished.
