Tung Oil as a Woodworking Finish
What it is
Tung oil, also known as China Wood Oil, Lumbang oil, Noix d'abrasin (fr.) or simply wood oil, is made from the seed kernels of the Tung tree (Aleurites fordii and Aleurites montana, family Euphorbiaceae). The A. fordii tree grows well in cooler climates, but can survive up to sub-tropical climates. A. montana is restricted to a more tropical climate. China, Argentina, Paraguay, Brazil and the USA are all major producers of tung oil.
Tung oil has been known about for hundreds of years in China, where it was used as a preservative for wood ships. The oil penetrates the wood, then hardens to form an impermeable hydrophobic layer (repels water) up to 5 mm into the wood. As a preservative it is effective for exterior work above and below ground, but the thin layer makes it less useful in practice.
When to consider it
Tung oil seeps into the grain of the wood, giving it a perpetual wet look that highly accentualizes the grain of the wood, commonly referred to as "making the grain pop". Because of this, the color of the wood is slightly darkened, giving the wood a rich, warm color that is very pleasing.
Tung oil provides a relatively hard surface finish that, as long as the surface integrity is intact, provides a waterproof finish that is impervious to dust, alcohol, acetone (nail polish remover), and various acids such as fruit and vegetable acids (orange juice).
Tung oil has a proven history in exterior applications, both above and below the soil level. Though the dried oil is relatively hard, the finish it provides is not the most durable. Tung oil is usually chosen for its aesthetic appeal rather than its wearability.
In its pure form, tung oil is a non-toxic finish that is ideal for surfaces that are expected to come into contact with food. This includes wood cutting boards, salad bowls, salt and pepper mills and any other project imagineable.