The right finish is vital to protecting your woodworking project from water damage and keeping it looking its best. Some of the most popular finishes are varnishes and stains, and you can usually find both at your local hardware store. A stain sinks deep into the wood to protect it from damage while a varnish sits on top of the wood to create a protective force field around it. Most woodworkers opt for either a polyurethane varnish or a tung oil stain. Both have pros and cons, but you should exercise caution if you opt for a wood finishing oil. Verify that the stain you buy contains tung oil as some manufacturers like to skimp on this important but sometimes costly ingredient.
Wood Finishing History
As early as 400 B.C., the Chinese used the oils from native tung trees (Vernicia fordii) to protect wooden structures and waterproof sailing vessels. Found only in nature, tung oil comes from drying and pressing the nuts of this tree. By contrast, polyurethane is a man-made polymer invented in 1937 by Otto Bayer as a replacement for rubber during WWII. Today this chemical makes its way into a stunning array of products including wood finishes, adhesives and foam.
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Tung Oil Trickery
Many of the products marketed as tung oil today aren't truly tung oil at all. Although the product manufacturers label their products as tung oil, some use a mixture of polyurethane and paint thinner instead. Before purchasing tung oil, check the package's ingredient list. The words "petroleum distillate" serve as the tip-off that the product really isn't tung oil at all.
Tung Oil Finish Versus Polyurethane
True tung oil soaks into the wood rather than sitting on its surface. It adds a pleasing amber tone to wood and is an excellent choice for detailed pieces that you want to keep looking natural. Because it penetrates, tung oil allows hand-carved and intricately worked pieces to maintain their detail. Tung oil isn't the best choice for high traffic areas, however, and is best avoided on heavily used furniture. Although tung oil can add water resistance to wood, wood treated with it is not considered 100 percent waterproof or safe for use outdoors. Even water resistance takes up to seven coats of oil. For maximum protection, you'll need to add a coat of tung oil to your wood once a year. Tung oil takes up to 48 hours to dry.
Polyurethane dries faster than tung oil and takes only 12 hours to cure. Polyurethane sits on top of the wood to form a protective barrier that is watertight in only two coats. When considering tung oil versus polyurethane for wood floors, polyurethane wins the contest every time. Because of the thick patina it leaves behind, however, polyurethane is not ideal for intricate woodworking such as scrollwork. Woodworkers wipe tung oil onto wood with a cloth while polyurethane gets applied with a brush, sponge or roller. These application methods apply a thicker layer of material and can hide the wood grain rather than accenting it. This is why woodworkers who want to emphasize the grain of the wood choose tung oil.