Pale Chromes. The great desideratum is to obtain a pale shade with the least quantity of sulphuric acid, or, which amounts to the same thing, the minimum of paleness with the maxi mum of staining power. As the shade deepens, the strength lessens; the orange chromes often contain orange lead, which is very objectionable.
Medium Chromes should give a clear golden tone with white lead, and not a buff. A fourth or third of zinc white mixed with the white lead holds the color better. The pale shades ought not to approach green; the grinding should be very fine, without any trace of grit.
Gamboge is a transparent color, only useful for glazing, lacquers, or for transparency paint ing, or for water-colors.
Green pigments, chiefly derived from the mineral sources of copper, are very plentiful and reasonable in price. Brunswick greens, quaker greens, chrome greens, etc., are all useful pig ments, owing their color to their preparation from the same mineral sources as Prussian blue and chromes. Generally, it may be granted that they are reliable and fairly permanent; but the painter will do well to avoid their use for tints with white lead in good and permanent interior work.
Bronze, olive, and invisible greens are, as their names imply, deep but richly-toned pig ments, very useful for external painting and very reasonable in price. They can be almost as easily mixed by compounding black and yel low pigments, or black, blue, and green, accord ing to the particular hue or cast that may be desired.
Emerald Green is made from arsenic. In oil it is permanent; when dry, it is so dusty and poisonous that there is danger in mixing it with water. It is a very assertive color, unharmoni ous and harsh. It is best to make up green with yellow and blue rather than use emerald green decoratively. A beautiful neutral green can be made by mixing yellow and black.
Paris Green is a crystalline color, and its rich ness of tint depends upon this. In grinding, a color of very fine crystal must be selected. To test this color for purity, dissolve out the oil by means of benzine, and dry the residue, then treat it with strong ammonia; if pure, it will entirely dissolve.
Verdigris is a transparent green, and, like the last color, is a copper compound entirely soluble in ammonia.
Madder Lake from the plant is the most per manent of the lake colors. That made from the
cochineal insects with salts of tin is not so per manent. The Venetians used to lay on their lakes without admixture over the plaster of Paris ground, and even then locked in the color by a rim of varnish, to protect it &cm the con tamination of any other color. The old Per sians would take a rug, dip it in a preparation of madder and milk, and then lay it in the hot sunshine, thus fixing it, and giving it a beautiful color. It is the modern dyer who takes the in sect cochineal, and, reducing tin with an acid, produces a red exceedingly brilliant, but not so beautiful as the old Persian red. Madder lake is more permanent. This cochineal color does not harmonize so readily with other colors, and is not so lasting as madder.
The tone of ocher ranges from pale yellow to brown; and there are several shades of red, as well as some other tones, produced by burning.
From the earliest days of history, ochers have been known and used, being of good body, and very reliable, if suitably prepared, for both oil and water painting. The variety of tone and shade in which they are to be found is endless, and to the action of iron is due the color of them all. As all varieties of ocher can be produced artificially and cheaply from iron, and since all native pigments require grinding and washing before being fit for painting, it need scarcely be added that the bulk of such yellow pigments used are of the manufactured kind. For making with white the very serviceable straw, stone, and buff tints for large plain surfaces, and the grounds for graining, the ochers are quite in dispensable. Ocher is too cheap for adultera tion, but it varies in staining power and in its tone. It is sometimes mixed with bad oil, and in other cases is not sufficiently washed. It is a permanent color, and harmless to the other colors. In oil it requires driers.