The Golden State: Where & How to Live, Secure, Visit, Enjoy and Thrive in California
Coloring Finishing And Painting Wood
Quick-Drying Varnish Characteristics And Ingredients
330. Origin of Drying-Speed and Purposes.—Acceleration or speed in the hardening of the rapid-drying or fourhour varnishes and enamels comes chiefly from the use of synthetic resins and partly from the proper heat treatment of the drying-oils which are used together with suitable driers. Synthetic resins are now manufactured for a great number of purposes, including use in clear varnishes for furniture, floors, and outside use; as well as for incorporating into enamels for finishes on wood and metal, for air-drying and baking, and to be applied with either brush on spray-gun.
It should be remembered that heat treatment in the varnish kettle may change the characteristics of a varnish to a very considerable extent. In making an ester-gum varnish with China-wood oil, it is important to give the oil proper cooking; consequently, temperatures of 525° F. to 560° F. are often used in the kettle. It should be noted that when synthetic gums are employed the China-wood oil and resins are heat treated at much lower temperatures than are needed for the proper cooking of ester-gum or fossil-gum varnishes.
331. Meaning of Term "Quick-Drying Varnishes."—It might be well to state that the term "quick-drying varnishes" is quite inclusive in meaning and is generally somewhat misleading. It would possibly be better to call them quick-setting varnishes because they set very quickly; but they dry hard only in perhaps about half or three-fourths of the time needed for slow-drying fossil-gum varnishes. Coatings of the so-called four-hour floor varnishes can sometimes be walked upon very carefully after four hours, but they are not really dry and should not be sandpapered and recoated for several hours more. The finisher should wait until such varnishes are really hard—usually 24 to 48 hours for floor varnishes—before sandpapering and recoating them.
332. Factors in Quick-Drying.—The quick-drying ingredients—synthetic resins chiefly—can be placed in various types of varnishes for numerous purposes, such as short-oil furniture and trim varnishes, medium-oil floor varnishes, and spar varnishes that are not very long in oil. Both gloss and flat surfaces are possible, as well as modification of these two types. It has been found that some of the synthetic resins are very durable in themselves, and that the addition of a large amount of drying-oils to make a spar varnish for waterproof use is unnecessary. Medium-oil, synthetic-resin varnishes can be made that are more durable than fossil-gum, long-oil spar varnishes of the old type.
In drying-speed the synthetic-resin, quick-drying Tarnishes are in a class by themselves. They come between the fossil-gum or ester-gum varnishes and nitrocellulose lacquers in speed of drying hard and especially in rapidity of setting. The quick-setting characteristic is usually of considerable value to the varnisher because less dust will settle into the sticky surface and fewer flies and insects will be caught than when slow-drying varnishes are used.
