Turpentine is a volatile, colorless liquid primarily derived from the resin of certain coniferous trees, most notably pines. It is an essential oil recognized for its potency as a solvent and its strong, characteristic resinous odor. This substance, sometimes known as “turps,” has historically played a significant role in maritime industries and the arts.
The Botanical Source in Pine Trees
The source of turpentine is not the watery sap of the tree but a viscous substance called oleoresin, which is a complex mixture of resin and volatile oil. This oleoresin is produced and stored within specialized structures known as resin canals, which run vertically and horizontally through the wood of pine species. The material is the tree’s natural defense response to injury, sealing wounds and inhibiting the entry of insects and fungi.
When the bark of a pine tree is damaged, the sticky oleoresin flows out to seal the breach, a process harnessed for human extraction. Historically important species in the United States turpentine industry included the longleaf pine (Pinus palustris) and the slash pine (Pinus elliottii). The quality and composition of the oleoresin can vary based on the specific pine species and the geographic location where it is grown.
Methods of Collection and Distillation
The traditional method of obtaining the raw material, known as the “naval stores” industry, involves a process called tapping or scarring. Harvesters make shallow, V-shaped cuts into the tree’s trunk, a practice that encourages the oleoresin to flow without causing fatal damage. The thick, honey-like substance, often referred to as gum or crude turpentine, is then channeled down the trunk and collected in small metal or ceramic cups attached below the cuts.
Once the crude resin has been gathered, the next step is distillation, typically using steam distillation. The collected oleoresin is heated in a still, and steam is introduced to vaporize the volatile components. This process separates the mixture into two distinct products: the lighter, volatile oil of turpentine and a heavier, non-volatile solid residue.
The vaporized turpentine is cooled and condensed back into its liquid form, resulting in the purified product known as “gum spirits of turpentine.” The solid residue left behind in the still is rosin, a hard, amber material that has its own commercial uses.
The Chemical Identity of Turpentine
The properties of turpentine are governed by its chemical makeup, which consists primarily of a complex mixture of organic hydrocarbons known as terpenes. These molecules, derived from isoprene units, are responsible for the strong, pungent pine-like odor and the effective solvent capabilities of the oil. The majority of gum turpentine is made up of two bicyclic monoterpenes.
The most abundant components are alpha-pinene, often comprising 60 to 80 percent of the volume, and beta-pinene, which typically constitutes 10 to 30 percent. The ring structure of these pinenes makes turpentine an excellent non-polar solvent, capable of dissolving organic compounds like oils and resins.
Key Modern Applications
While its use as a household paint thinner has largely been replaced by cheaper petroleum-based alternatives like mineral spirits, purified turpentine remains an important industrial material. It is a highly effective specialized solvent, particularly valued by artists for thinning oil-based paints and cleaning brushes without leaving a residue.
The most significant modern use of turpentine is as a foundational raw material in organic synthesis. The isolated pinene components are chemically processed to create a variety of other valuable compounds. These derivatives are used in the manufacture of synthetic camphor, pine oil for cleaning products, and various fragrance chemicals. The oil’s natural antiseptic and deodorizing qualities have also led to its inclusion in some specialized cleaning and sanitary products.