It is generally known that this oil is pressed from the fruit of a tree which is named by the Chinese, on account of the bottle-shaped form of the nuts it bears, tung yu or ying tzu tung, also tung tze chou, hence the name tung oil, and because of its home being China, we have the commercial term China wood oil. A similar oil, which the Japanese term Dokuye-no-Abura, is produced in Japan from trees named Abura-no-ki, Abura yiri and Yama girl, and all of these trees, including the tung tree of China, belong to the groups that are known by the botanical names Aleurites cordota and Aleurites Fordii. It has been contended by some botanical authorities that the last named is the mother plant of all and that from its fruit the best oil is produced, but this has yet to be proven. At any rate, the China wood oil, as it is imported into this country from Hankow, has always had the preference over that obtained from other sources.
The tung tree and its products have found many varied uses for centuries past in its home. The Chinese hold it in the greatest esteem on account of the many benefits derived from it. The wood of the trunk of the tung tree, while it is still young, is white and soft, but as it grows becomes harder, until at last it is impenetrable by water and resists the attacks of insects. The fiber of its wood may be woven into very durable matting, etc.
The tree grows best and bears best fruit south of the Yangtse Kiang River in the provinces of Kingsi, Tschekian, Hunan, Hupeh and Szetschwan, where it is grown for oil production, and where it will grow even in a ground of sand and gravel, while to the north of this territory it is simply grown as a shade tree, because in that climate it will bear but little fruit and above the thirty-fourth degree northern latitude it will not grow at all.
The fruit of the tung tree is a nut, that, as before stated, has the form of a bottle, the inner shell of which is similar to that of a walnut, containing from 3 to 5 kernels, each of which is about the size of a large hazelnut. The outer shells of the fruit from the trees of the Aleurites cordota are shriveled in appearance, those of the Aleurites Fordii quite smooth. The tung tree does not require nursing, the greatest height attained by it is from 22 to 25 feet, and from the fourth year on, it will bear from 20 to 50 pounds of nuts annually for about ten or twelve years, when it ceases to be productive.
China wood oil, or tung oil, is often confounded with Bankul oil, which is produced from the nuts of the trees belonging to the botanical group Aleurites triloba, that grow on the South Sea Isles, the islands of the Malay archipelago and Reunion Islands, as well as in the East Indies. The kernels of the nuts from these trees, which grow to a height of from 36 to 45 feet, yield 60 per cent and over of their weight of oil, which is used as a substitute for linseed oil, especially in printers' colors.
When tung oil was first more generally introduced the technical people became slightly mixed as to its proper name, and Chinese wood oil was the term often used, until it finally crystallized itself into China wood oil in the world of commerce and tung oil among the technical world. Simply to designate it as wood oil is rather confusing, as this term has also been used for Garjun balsam and for wood turpentine and pine oil. At the present time, however, it is safe to say that any one interested in the article will know the meaning of the term China wood oil or, if the shorter name is preferred, tung oil.