The Best Finish Oil That Will Not Darken Wood

Available Finishing Oils

• The penetrating oil finish that has the longest history in Western woodworking is linseed oil. Derived from flax seeds, it's a hardening oil; it cures to seal the grain and provide a small measure of impact resistance. In the early 20th century, American woodworkers began to use tung oil, a hardening oil that comes from the nuts of the tung tree, which grows in China. More recently, a third hardening oil -- rosewood oil -- has appeared on the shelves. This oil comes from the seeds of Brazilian rosewood trees. In addition, woodworkers use a number on nondrying oils, such as walnut, peanut and edible mineral oil to treat wood for food-serving applications.

Darkening Effects of Oil Finishes

• Of all the oil finishes, linseed oil is the one that has most effect on wood color. It imparts an amber hue that deepens as you add more coats. This effect is less pronounced when using tung and rosewood oil, but because both oils penetrate the grain, they darken the wood somewhat. The darkening effect is more noticeable on open-grained woods like oak and pine than it is on close-grained ones like maple. Nondrying oils also darken the wood when fresh, but because they don't harden, they eventually wear off. When they do, the wood regains its natural color, and that's usually a sign that it needs recoating.

Wiping Varnishes

• Some products identified as penetrating oils are not oil at all but varnish thinned with petroleum distillates. Even though the label identifies a product as tung oil, if it lists petroleum distillates as an ingredient, the product is probably a wiping varnish. Thinning the varnish allows it to penetrate the grain of the wood, and when it hardens, it seals better than oil and provides more impact resistance. It's possible to make your own wiping varnish by mixing alkyd or polyurethane varnish with mineral spirits. As the name implies, you apply it by wiping on small amounts with a rag.

The Best Choice

• Putting linseed oil aside because of its propensity for yellowing, the best choice of finishing oil depends on the wood species and the purpose the finished wood will serve. All oils, including nondrying ones and wiping varnishes, make the wood look wet. Penetrating oils lack the luster of wiping varnishes, however, so if you want the wood to look as natural as possible, use tung or rosewood oil. You'll probably have to build up several coats, sanding in between, to get a suitable finish. Wiping varnish, on the other hand, protects with as few as two coats. Avoid hardening oil and varnish when finishing cutting boards and other food-service items; treat them with food-safe mineral or vegetable oil.