Soft Resin

a resinous material that is produced upon wounding of coniferous trees; it is present in the resin channels that permeate the wood of the pine, cedar, fir, and larch. Solidifying on the surface of the trunk, soft resin protects the wood from penetration by bark beetles and fungi, “healing” the wound (hence the Russian name, zhivitsa, from zazhivliat’ “to heal”).

Soft resin is a basic raw material in the production of rosin and turpentine. It is produced by making a series of shallow incisions on the trunks of growing trees (so-called tapping). The yield of soft resin depends mainly on the species or kind of wood and on climatic conditions. In the USSR the tree most suitable for tapping is the Scotch pine (Pinns sylvestris), which yields 0.9–2.0 kg of soft resin per tree per year. Soft pine resin is a viscous, transparent liquid with a pleasant pine odor. It consists of a volatile part (turpentine) and nonvolatile resin acids (rosin), with water as an impurity. Soft resin thickens in air because of evaporation of the turpentine and crystallization of resin acids, and it becomes turbid, like saccharified honey. The soft resin delivered to refineries contains about 75 percent rosin, 18 percent turpentine, and 6 percent water. The processing of soft resin involves purification and steam distillation of the turpentine, with simultaneous melting of the solid resin acids.