Turpentine
Turpentine, an oleoresin (a mixture of oil and resin) contained in the bark and wood of some coniferous trees. The term turpentine is also used to refer to the oil refined from the oleoresin. This oil—often called oil of turpentine or spirits of turpentine—is a colorless, volatile liquid with a strong odor. It is used primarily as a solvent and thinner for oil-base paints and varnishes. The resin, which is called rosin, is used on violin bows and in sizing paper.
Turpentine is produced from many different kinds of coniferous trees. In the United States the longleaf pine and the slash pine are the chief sources of commercial oil of turpentine. When living trees are the source, the product is called gum turpentine. Wood turpentine is obtained from stumps and the branches of cut-down trees. Most of the turpentine produced in the United States is sulfate turpentine. It is obtained as a byproduct of the sulfate (or kraft) pulping process used for making paper.
To produce gum turpentine, diagonal cuts are made in the bark and sapwood. Troughs are wedged into the grooves to carry the oleoresin that oozes out of the cuts into a small container. After the oleoresin is collected, it is distilled to separate the oil from the resin.
Wood turpentine is usually produced by treating wood chips with a solvent called naphtha. The solvent draws out the oleoresin from the wood. The solution of naphtha and oleoresin is then distilled to recover the naphtha for reuse and to separate the oil and resin.
In the sulfate pulping process, wood is heated and broken down with chemicals in large tanks called digesters. Sulfate turpentine is obtained by distilling vapors removed from the digesters. The resin is recovered from the liquid residue of the pulping process.