White zinc is a somewhat purer white than white lead; not so opaque. Three coats of lead are reckoned equal to five coats of zinc. It becomes harder than lead, but is somewhat liable to peel off; while lead, after exposure to the air for a long time, becomes dry and powdery on its surface, and chalks.
A mixture of two parts of lead and one of zinc is much liked. Zinc-lead, however, is the name of an entirely different pigment, made by furnacing ores containing about equal parts of lead and zinc, in which the lead is present as a sulphate. This pigment is free from the liability to turn brown if exposed to sulphur gases; it is said to be not quite so pure a white as the preceding. It is a comparatively new pigment, but is coming rapidly into use, being somewhat cheaper than the others. Lithopone is another white pigment of considerable merit.
From these white paints, colored paints are made by adding tinting colors, of which the yellow is chiefly chrome yellow, or chromate of lead; the blue may be either ultramarine or prussian blue; and the green is chrome green, a mixture of chrome yellow and prussian blue. The reds are (in house paints) made from coal-tar colors, and most of them are now fairly fast to light. Some dull yellow colors are made from ochers, which are clays tinted with iron oxides, roasted and ground. These are permanent colors.
The dark-colored paints may not contain lead or zinc at all. The deep yellows, greens, and blues are made from the colors already named as tinting colors, none of which are entirely fast to light; the dark reds and browns are chiefly iron oxides, which are a valuable class of paints"' very permanent on wood. The blacks are either lamp black or drop-black (bone-black) and other carbon colors; and these are often added in small quantity to secure some desired tone or shade of color.
The zinc and lead pigments have some action on oil, and in their case it is considered the best practice to apply thin coats; but the dark pigments do not act on oil, and, of these, thick coats are best for dura bility.
to recommend it will prove a poor investment. If properly cared for, brushes last a long time, and it pays to have good ones. The first sign of a good brush is uniform quality from outside to center. Inferior brushes have inferior bristles in the middle, and some poor brushes are actually hollow. For ordinary oil painting, the bristles on a large new brush should be five or six inches long, uniformly flexible, and as stiff as can be found; they will be flexible enough anyway, but all should be alike.
Paint brushes are round, flat, or oval. A favorite brush for ordinary outside work is what is called a pound brush, a large, round brush with stiff bristles six .inches long. Such a brush should be bridled when it is new—a "bridle" being a piece of cord wound around the bristles to shorten their effective length; as the bristles become worn off, the bridle may be removed. A 21-inch oval brush (2i inches wide) is a highly satisfactory tool to use in general painting, and is the brush recommended by the paint committee of the American Society for Testing Materials. It is worth noting that this committee, made up equally of expert paint manufacturers and experts employed by the large consumers, unanimously agreed that no larger brush than this should be used in making paint tests.
The use of brushes five inches wide is common for outside work; but while such brushes may be had of the best quality, they are heavy and laborious to use, and the workman who uses such a brush will not brush the paint sufficiently to get the best result. If a flat brush is used, it should not exceed 31 inches in width; and three inches is better. A good 21-inch oval varnish brush is a most excellent brush for all large work in either paint or varnish. The painter should also have a good 11-inch oval brush for smaller work, and a number of round or oval brushes, called sash tools, of different smaller sizes, for more delicate work, such as sash and frame painting. Stiff-bristle brushes, which have been worn off short, are suitable for such work as rubbing-in filling. For varnishing large surfaces, flat bristle brushes 21_ inches wide are good; also similar ones 2 inches, 11 inches, and 1 inch wide are useful. All flat brushes should have chiseled edges. For flowing varnish, it is necessary to have thick, flat, camel's-hair brushes, running up to 31 inches in width, although most house varnishing may be done with brushes not over 21 inches wide.