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Tung oil comes from the seeds of several species of Aleurites, primarily Aleurites fordii, a deciduous shade tree native to China. It belongs to the Euphorbia Family (Euphorbiaceae) along with the candlenut tree (A. molucanna), another species with seeds rich in unsaturated oils. For centuries tung oil has been used for paints and waterproof coatings, and as a component of caulk and mortar. It is an ingredient in "India ink" and is commonly used for a lustrous finish on wood. In fact, the "teak oil" sold for fine furniture is usually refined tung oil. Some woodworkers consider tung oil to be one of the best natural finishes for wood.

Other unsaturated plant oils, such as castor oil and linseed oil, take longer to dry and leave an oily residue until they soak into the wood surface. Tung oil 's ability to dry quickly and polymerize into a tough, glossy, waterproof coating has made it especially valuable in paints, varnishes, linoleum, oilcloth and printing inks.

Tung oil is composed primarily of eleostearic (elaeostearic) acid, with smaller amounts of oleic, linoleic and palmitic glycerides. Eleostearic acid is a crystalline unsaturated fatty acid that exists in 2 stereoisomeric forms: An alpha acid occurring as the glycerol ester especially in tung oil, and a beta acid obtained from the alpha acid by irradiation (9, 11, 13-octadecatrienoic acid). The following table shows the chemical structure of tung oil eleostearic acid:

Although the closely related candlenut tree (Aleurites molucanna) is also native to Asia, it has been spread by people throughout the tropical Pacific because its seeds are rich in oil. The valuable oil expressed from seeds is used as a light source and as a mild cathartic. Seeds were strung together and burned like a candle.

Shelled candlenuts (Aleurites molucanna) are commonly sold in Asian food markets. Although they superficially resemble shelled macadamia nuts, they should not be eaten raw because they contain a strong purgative. Apparently roasted seeds are eaten, but only in small quantities because of their laxative effect. In Hawaii they are roasted and made into a condiment called inamona, by pounding them into a paste that is mixed with salt. The inamona paste is mixed with seaweed, minced chile peppers and bite-sized cubes of raw ahi fish (or another fish) to prepare a favorite Hawaiian dish called "inamona poke." The cooked, mashed seeds are used in a similar Indonesian dish called "sambal kemiri." Candlenut paste is also used to thicken and flavor Indonesian and Malaysian curries.

In the Hawaiian Islands candlenuts are known as "kukui nuts" and are polished and made into shiny dark brown or black bracelets and leis. The actual "nut" is a thick-walled seed within the endocarp layer, typically one or two seeds inside each fruit. Most references consider the kukui fruit to be a drupe or drupaceous nut. The leathery, green outer layer (mesocarp and exocarp) is similar to the husk of a walnut, and the thin inner layer surrounding the oily seed is a stony endocarp. In the closely-related tung oil tree, two-several seeds are contained within a chambered, woody endocarp (see tung oil photo).

Hard-shelled kukui nuts take such a brilliant luster that they resemble polished gemstones. There are several variations in the polished nuts, including smooth and grooved. Color variations include black, brown, light brown, marble and white. The nuts are strung whole, half-shell, or in fragments of the seed shell. A step-by-step guide on how the kukui nuts are drilled and strung onto satin ribbon is explained in Hawaiian Seed Lei Making by Laurie S. Ide (2001). Throughout the islands the light green (silvery-gray) foliage decorates lush canyons and valleys. The light-colored foliage is easy to spot from the numerous vistas on these lovely islands. Candlenut seeds occasionally drift ashore on islands of the Caribbean and are known locally as "Jamaican walnuts" because of their superficial resemblance to an unshelled walnut.

According to the United States National Herbarium, the official state tree of Hawaii is the kukui nut. Unlike the state flower, the yellow Hibiscus brackenridgei, Hawaii's official state tree is not native to the Hawaiian Islands. The kukui nut was legislated in 1959 because of its historial significance in the colonization of Hawaii by native Polynesians. Today it is a widespread tree throughout the islands.

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