Varnishing is the last process of house-paint ing, and consists in covering the pigments with a film of a transparent resinous nature, which not only preserves the paint from the ill effects of the atmosphere and handling, but brings out the color of the pigment to its fullest extent. Where paint is prepared with an excess of raw linseed or boiled oil, varnishing is not necessary, since the oil itself encases and protects the par ticles of the pigment or solid used, and by its smoothness and body maintains a good gloss. With better-class work, and graining and mar bling, a protective body of oil varnish is desir able, but experience and knowledge are neces sary to discriminate between the varied kinds that are made.
As varnishes come to the painter, it is quite impossible that he should know the composition of the material he is using; only the reputation of the maker can be his guide, as the varnishes that are made owe their excellence to the exact ness and perfection of their manufacture.
Although the best of varnishes are made from gums, yet the excellence of the varnish is a great deal due to the process of manufacture; and although varnish is made by melting the gum in raw linseed oil, yet to put oil to varnish once made would destroy its drying power.
Varnishes may be considered in three classes —as expressed oil varnishes, volatile oil var nishes, and spirit varnishes; and from these terms some notion of the solvents or liquids they are compounded from is gathered. It is custom ary to further distinguish them by the substance or resin they contain, such as copal varnish and mastic varnish; and again by their probable use, as oak varnish and maple varnish.
The most serviceable varnishes for use in connection with painting belong to oil varnishes, and these are usually copal—the name given to the gum principally used in their manufacture. Copal gum in appearance somewhat resembles amber, and it is imported from the tropics. When varnish makers purchase a parcel of gums, the pieces are very carefully assorted into various degrees of lightness and transparency. The whitest variety of the gum is usually the scarcest; and as it follows that the color of the copal must exercise a considerable influence over that of the ultimate product, white copal varnish is consequently found a most expensive prepara tion.
Generally, in the manufacture of copal var nishes, the gum is first dissolved by heat, and then converted by turpentine into the liquid form, with the addition of linseed oil, to give the copal elasticity. The color of the oil used is, therefore, a further important factor.
Colorless varnish, such as that known as mastic, can be made by simply dissolving picked gum mastic in oil of turpentine; but since the ab sence of linseed oil causes the liquid to set and harden very rapidly, such a preparation would be practically useless for the house-painter, be sides lacking in that elasticity and body which it is the special property of linseed oil to con tribute.
For the house-painter's finest work, white oil varnish—that is, a liquid which can be spread and worked upon broad surfaces, and such as will dry in about eight hours—is very requisite. The chief attributes aimed at are freedom from yellowness and the possession of good "hand polishing" qualities.
A good friend is hard-drying or church oak varnish, although in copal oak varnish quickness of hardening must generally be accompanied by a tendency to lose gloss and to crack, from excess of resin. A preparation known under the above names is always to be had for seats of public buildings, stained floors, and common furniture, for which it is most valuable. This make of varnish is also used for kitchen furniture, since, unlike many and even expensive painters' var nishes, it does not get soft and sticky from the warmth of the body, while its oily nature makes it very durable. The litharge or similar sub stance with which it is prepared, however, con siderably darkens the oil, so that this would not do for light-colored paint.
Maple Varnish is but another name for a good quality of interior copal varnish, made from the palest gums and refined oil, so that when coated over such delicate figure as the imitation of maple and satinwood, it shall not disadvantageously affect the color of the grainer 's work beneath.
The varnishing of wall-papers is an impor tant item of painters' work, and covering the walls of middle-class houses with pattern papers suitable for varnishing on staircase, bathroom, and kitchen walls especially, is a practice con sistent alike with sanitation, durability, and dec orative effect. For use on all paper hangings on which the yellowness of copal varnish would not be detrimental to the color of the design, a good quality of this variety is far preferable to the paper varnishes sold by the manufacturing houses. Whether used upon walls or woodwork, the color of copal oak varnish would spoil such tints as French or green-greys, delicate pinks or white; but for terra-cotta shades, buffs, leather, or cinnamon colors, the yellowness would be no disadvantage.