Page:Cyclopedia of Painting-Armstrong, George D (1908).djvu/248

240 used for delicate works where the length of time required for drying is no object. It is much celebrated in some old books, under the name of oil of pinks and oil of carnations, as erroneously translated from the French œillet, or olivet, a local name for the poppy in districts where its oil is employed as a substitute for that of the olive. It is, however, inferior in strength, tenacity and drying to linseed oil, although next to it in these respects, and, though it is of a paler color, and slower in changing, it becomes ultimately not so yellow, but nearly as brown and dusky, as linseed oil, and therefore is not preferred to it.

Nut Oil is the oil of walnuts, and is used in ornamental painting, as it is nearly colorless, and can be used with flake white and other delicate colors without the slightest danger of tingeing them.

Driers. Driers are used to hasten the drying of paints. These are ground up in oil and are mixed in small quantities with the color; some colors, in fact, will not perfectly harden without them, but remain sticky, or, as painters term it, tacky, until sufficient dust has clung to them to render their external surface at least apparently dry; though, as can be well understood, it will remain disagreeable to the touch and much injured in color. Red lead is a good drier, but, of course, can only be used in situations or in paints where its color is not objectionable. Sugar-of-lead is, however, the best drier, but is more expensive than others. Patent driers, ground up in oil, may be purchased at the various paint stores.

Drying Oils. All the fixed oils have an attraction, more or less powerful, for oxygen, and by exposure to the air they either become hard and resinous, or they only thicken slightly and become sour and rancid. Those which exhibit the first property in a marked degree—as the oils of linseed, poppy, rape and walnut, are called drying oils, and are used as vehicles for colors in painting; the others are termed glutinous or non-drying oils.