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Coloring Finishing And Painting Wood

140. Resins Used in Spirit-Varnishes.—Various resins, frequently in mixtures, are used in spirit-varnishes. The solvents which are most commonly selected are turpentine or alcohol, altho many of the resins will dissolve, either wholly or in part, in benzol or ether. It should be remembered, however, that some resins are largely or entirely soluble in turpentine and only partly soluble in alcohol. In other cases the reverse is true. The following lists indicate the solvents that can be used with several of the resins:

Soluble in turpentine or benzol	Partly soluble in turpentine or benzol
Dammar Mastic Rosin	Sandarae (26% to 33%) Manila gun, hard (27% to 36%) Manila gum, soft (36% to 42%)
Soluble or nearly soluble in alcohol	Partly soluble in alcohol
Sandarae Sllellac Rosin Elemi Manila gum, soft Benzoin	Dammar (71%) Mastic (64%) Brazilian copal (62% ) Manila gum, hard (44%)

THREE USEFUL SOFT GUM VARXISHES

141. Dammar-Varnish.—The best known of the clear or transparent varnishes commonly sold on the American market is called dammar-varnish. This resin, classed as a soft resin, comes from the East Indies, is harder than rosin, but is much softer than are the copals in general. Dammar resin is frequently dissolved in turpentine in which substance it is almost completely soluble; while, if alcohol is the solvent, there is about 29 per cent of residue remaining which is insoluble.4 Other solvents which are sometimes used in dammar-varnishes are carbon tetrachloride, benzine, heavy naphtha 48°, and heavy benzol.

Dammar-varnish when spread upon a surface does not show the brilliancy of a shellac finish, nor does it have the durability of good fixed-oil varnishes which include linseedoil or some other drying-oil in their composition. In such finishes, the turpentine, alcohol, or other volatile solvent dries out leaving a thin film consisting of the gum or gums spread over the surface.