Carmine, made from the cochineal insect, is the most brilliant red color known. It is, however, too expensive for ordinary house painting and is not durable. It is sometimes used for inside decoration.
Red lead is produced by raising massicot, which is the commercial name for oxide of lead, to a high temperature, short of fusion, during which it absorbs oxygen from the air and is converted into red lead or minium, also an oxide of lead. The color is lasting, and is unaffected by light when it is pure and used alone, but any preparation containing lead or acids mixed with it deprives it of color, and impure air makes it black. It may be used for a drier, as it possesses many of the properties of litharge; it is also often employed in painting wrought iron work, to which it adheres with a tenacity not equaled by any other paints; it is sometimes objected to for this purpose, on the ground that galvanic action is set up between the lead and iron.
Vermilion is a sulphide of mercury in a natural state as cinnabar. The best comes from China. Artificial vermilion is also made, both in China and in this country, from a mixture of sulphur and mercury. Genuine vermilion is very durable, but when mixed with red lead, as it is sometimes, it will not stand the weather. It can be tested by heating in a test tube; if genuine it will entirely volatilize. German vermilion is the tersulphide of antimony, and is of an orange-red color.
Indian red is a ground hematite ore brought from Bengal; it is sometimes made artificially by calcining sulphate of iron. The tints vary, but a rosy hue is considered the best. It may be used with turpentine and a little varnish to produce a dull surface, drying rapidly, or with boiled oil and a little drier to produce a glossy surface.
Fig. 17. Flat Knotted Badger Blender.
Tuscan red is essentially a mixture of Indian red with some sort of lake color. The cheapest article is made from a reduced Indian red and rose pink. The richness of such article is very fleeting, particularly if the rose pink be simply whiting colored with a coal tar dye. It is apparent that the real value of a Tuscan red lies in the permanency of the lake coloring material employed to give it richness.
Orange is a chromate of lead, brighter than vermilion. but less durable. Orange ochre is a bright yellow ochre burnt to give it warmth of tint; it dries and works well in water or oil, and is very durable. It is known also as Spanish ochre. Orange red is produced by a further oxidation than is required for red lead. It is a brighter and better color.
Chinese red and Persian red are chromates of lead, produced by boiling white lead with a solution of bichromate of potash. The tint of Persian red is obtained by the employment of sulphuric acid.
Venetian red is obtained by heating sulphate of iron produced as a waste product at tin and copper works. It is often adulterated by mixing sulphate of lime with it during the manufacture. When pure, it is called bright red. Special tints of purple and brown are frequently required, which greatly enhance the value of the material. These tints should be obtained in the process of manufacture, and not produced by mixing together a variety of different shades of color. When the tint desired is attempted to be obtained by this latter course it is never so good, and the materials produced are known to the trade as faced colors, and are of inferior value.
Venetian red originally consisted of a native ferric oxide or red hematite. But of recent years the name appears to have been transferred to a particular quality of artificial ferric oxide made by calcining green vitriol. When this salt is heated in a crucible the upper portion of the product, which has been less strongly heated than the lower, is of a brighter red than the remainder, and after washing and grinding is sold as Venetian red.
Lakes are made by precipitating colored vegetable tinctures by means of alum and carbonate of potash. The alumina combines with the organic coloring matter and separates it from the solution. The tincture used varies in the different descriptions of lake. The best, made from cochineal or madder, is used for internal work. Drop lake is made by dropping a mixture of Brazil wood through a funnel onto a slab. The drops are dried and mixed into a paste with gum water. It is sometimes called Brazil wood lake. Scarlet lake is made from cochineal, so also are Florentine lake, Hamburg lake, Chinese lake, Roman lake, Venetian lake and Carminated lake.