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spirit varnish[′spir·ət ‚vär·nish]
any one of various solutions having a concentration of between 30 and 40 percent of certain resins in 90–95 percent ethyl alcohol. The film-forming substances include natural resins, such as shellac, soft copals, sandarac gum, mastic, rosin, and acaroid resin, and synthetic phenol-formaldehyde novo-lac resins, for example, iditol. To improve the resilience of the coatings, spirit varnishes are plasticized with, among other substances, castor oil and fatty acids of linseed oil. Upon the introduction of such alcohol-soluble organic dyes as aniline black and rhodamine into spirit varnishes, black and colored varnishes are obtained. The dispersion of inorganic pigments in spirit varnishes yields enamel paints or spirit enamels.
Spirit varnishes are applied to surfaces with a brush or cotton wad; several layers are applied, at intervals up to 10 min. The film formed through the evaporation of the solvent retains its solubility in ethyl alcohol; the film’s gloss can be enhanced with polishing, but the film is not resistant to the action of water and to sharp temperature fluctuations. Until the 1930’s, spirit varnishes were the principal materials used for the finishing of wooden items (furniture, musical instruments, toys) as well as of leather, paper, and glass. Spirit enamels were used to paint wooden casting molds. With the development of methods for the production of paints and varnishes from synthetic film-forming substances, many of which are not soluble in ethyl alcohol, the industrial importance of spirit varnishes has diminished.
M. M. GOLDBERG