Tung Oil – Source and History
by Eric Krum
Tung oil or China wood oil is obtained by pressing the seed from the nut of the tung tree (Vernicia fordii). Tung oil hardens upon exposure to air, and the resulting coating is transparent and has a deep, almost wet look. Used mostly for finishing/protecting wood, after numerous coats the finish can even look plastic-like.
The oil and its use are believed to have originated in ancient China and appear in the writings of Confucius from about 400 B.C. Raw tung oil tends to dry to a fine wrinkled finish to stop this, the oil is heated, also known as “boiled”.
The name is often used by paint and varnish manufacturers as a generic name for any wood finishing product that contains the real tung oil and/or provides a finish that resembles the finish obtained with tung oil.
The tung oil tree originates in southern China and was cultivated there for tung oil, but the date of cultivation remains unknown. During the Song Dynasty, tung oil was used for waterproofing on ships. The earliest references for Chinese use of tung oil is in the writings of Confucius around 500 to 400 BC. The Chinese have used tung oil, also known as China wood oil, for at least 2500 years for building waterproof boats and paper parasols, wood finishing, wood waterproofing, caulking, inks and paints. Marco Polo wrote in the 13th century “The Chinese take some lime and chopped hemp, and these they knead together with a certain wood oil; and when the three are thoroughly amalgamated they hold like any glue, and with this mixture they paint their ships”.
The wood of the tree is lightweight and strong, and is sometimes used as a substitute for balsa or basswood. The tung tree is poisonous in all of its parts, including the fruit and the seeds, although some parts of the tree have been used for medicinal purposes in the past.
Editor’s Note: Eric gave a presentation on wood finishes at our January meeting. You can download it here.