Pine-Tree Products.—The various members of the pine and cone-bearing trees yield valuable essential oils and oleo-resins that are very important in the arts and sciences. These, in nearly every instance, are prepared from the sap of the tree.
Oil of turpentine is known as an "essential oil," and in chemical structure and properties it does not differ from the various essential oils, such as lemon, orange, peppermint, etc. Commercial turpentine is generally made from the sap of the long-leafed pine of the Atlantic coast-plain.
The bark of the tree is cut near the foot, and the sap that oozes from the scar quickly hardens into a gum. The gum, generally known as "crude turpentine," is distilled and yields about one-fourth its weight of oil or "spirit" of turpentine. It is a staple article of manufacture in Europe, India, and the United States, and is used chiefly to dilute the oil paints and varnishes used in indoor work. The United States supplies about two-thirds of the world's product, a large part of which is shipped from Savannah and Brunswick, Ga., to Great Britain.[40]
Resin is the substance remaining after the crude turpentine has been distilled. It is used in the manufacture of varnish, sealing-wax, and soap. Finely powdered resin is also mixed with wood-pulp in the manufacture of wrapping-paper. It gives the latter a glazed surface and renders it almost water-proof. Most of the world's product of resin comes from the turpentine district of the United States, and about four-fifths of it is exported to Europe.
When resin is subjected to distillation at a still higher temperature, resin oil, a very heavy turpentine, is given off, and a viscous substance known as pitch remains. A considerable amount of this is still made in the United States, but the greater part comes from the pine-forests of Russia and Scandinavia. When pine-wood is distilled, tar is the chief product. In Russia tar is generally made by burning green logs covered with turf, over a pit. Creosote, or wood preservative, is made from tar. The various pine-tree products, creosote excepted, are commonly known as "naval stores," the tar being used in water-proofing the rigging of vessels, the pitch in calking the seams in between planks, in the decks and hulls.
Other Resins and Gums Used in the Arts.—Most of the gums and resins used in the arts and sciences are the hardened sap of plants—in some cases exuding by natural means from the bark, in others resulting from the puncture of the bark.
The lac of commerce is due to the puncture of the young branches of a tree, frequently a fig (Ficus religiosa) growing in the tropical forests of India. The hardened sap incrusts twigs forming stick-lac; when crushed, washed, and freed from the woody matter it is seed-lac; when melted and cooled in flakes it is shell-lac, the form best known in commerce. It is the chief ingredient in sealing-wax, and is extensively used as a varnish. It is also used in fireworks on account of its inflammability.
Dammar is the product of a tree growing in the East Indies; it is the basis of a very fine white varnish. Copal is a term applied to oleo-resins soluble in turpentine, and used almost universally as varnishes. They come from the tropical regions of South America, Africa, and from the East Indies. Kauri is the fossil gum of a cone-bearing tree dug from the ground in northern New Zealand. Amber is the fossil gum of extinct cone-bearing trees found mainly along the Baltic coast of Prussia. It is used chiefly for the mouth-pieces of tobacco-pipes and cigar-holders; the inferior product is made into varnish. It is sold wherever tobacco is used. Sandarach, found on the north African coast, is used principally in Europe, being employed as a varnish. The United States and Great Britain consume most of the foregoing products.
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