List of therms» Turpentine

Except of lithotine, turpentine is the chief solvent used in the lithography workshop. Gum spirits of turpentine is a slightly oily liquid obtained by the dry distillation of natural resins of southern pines. Steam-distilled turpentine is obtained by the steam distillation of the resinous wood from the trees. Either type is satisfactory for lithography, although the gum spirit is preferable because of its less objectionable odor.

Turpentine is an excellent grease solvent and evaporates reasonably quickly. It may be used for washing out work on stone or metal plates and may be incorporated in tusche mixtures for drawing purposes. Upon aging, it absorbs oxygen, forming a resinous substance that remains in the solution but is not volatile. Most commercial turpentines contain 1 to 4 % of this resinous substance, which is beneficial to lithography. When the printer washes the ink from the printing surface with turpentine, most of the solvent evaporates, but the nonvolatile resinous part remains as a thin coating on the image areas. This allows them to accept ink readily, which they do not do when petroleum solvents such as benzine or gasoline are used for the washout.

Anna Trojanowska