PAINTS, PAINTERS' COLORS, or PIGMENTS. These names are applied to the prepared or unprepared compositions by which wood, stone, and other materials are coated with a preservative surface of oil, mixed with an earthy matter to give it color and consist ency; also to the materials used by artists to produce the colored surfaces of their pictures. The art of painting in its primitive state consisted merely in applying such natural, mineral, and vegetable colors as were spontaneously yielded, without any vehicle to render them permanent, consequently they had to be renewed as often as they were rubbed or washed off from the surfaces to which they were applied. The paints now in use arc nearly all mixed with a liquid vehicle, and are applied in the liquid state. The mixing materials arc varied according to the requirements of the work. Thus for some kinds of decorative work, and for water-colo• drawings, gum, glue, size, or other adhesive materials dissolved in water, are employed; whilst for the of build ings, etc., and for oil-paintings, oils of various kinds are used for mixing and thinning the colors. Thus, for painted work exposed to the weather, it is found that linseed oil boiled with the sulphates of lead (litharge) or zinc, or with acetate of lead (sugar of lead), is the best. The preparation of boiled oil is one requiring particular care, as it is desira ble to have it bright and clear. Hence the proportions of the metallic salts are much varied by different manufacturers, and by some various other ingredients arc added. The time of boiling and the method of filtering are also much varied.. For indoor work, plain linseed oil and oil (spirit) of turpentine are used; if a glossy slopes is wished, the linseed oil must be in excess; if a dull or flattened smface, then the quantity of turpen tine, or (nips, as it is often technically called, must be ,increased; and it is usual to add a small quantity of ground litharge and sugar of lead, which are prepared for this purpose, and sold under the name of driers. For artists' colors, very fine linseed or nut oil is used, unboiled, and in small quantity, and turpentine is employed to dilute them. Paints for very rough purposes, such as ship-work, stone walls, etc., are often mixed with whale oil boiled with white vitriol (acetate of zinc), ]itharge, and vinegar, and they are diluted with common linseed oil and turpentine.
Most of the paints used for ordinary purposes are composed first of the coloring matter, then of a quantity of white-lead, with which and the oil they are worked into a paste of the shade required, and afterwards thinned down with oil and turpentine when used. The white-lead which thus forms the basis of most paints, and by itself a color, is a carbonate and oxide of the metal, produced by exposing pieces of lead to the action of the steam of acetic acid in beds of fermenting tan. It is the principal white paint
used. but is liable to discoloration from the gases contained in impure atmospheres. Oilier white pigments are prepared from the oxide of zinc, and the carbonate and sul phate of barytes. Pale yellow is made with chromate of stroutian, orange-yellow with sulphuret of cadmium, whilst several varieties of this color are produced by chromate of *a lead, sulphuret of arsenic, or king's yello , and various native earths in which silica and alumina are combined with oxide of iron. Amongst these are yellow ochre, Oxford, Roman. stoic, orange, Indian, and American ochres. Reds are either purely mineral, or they are lakes, i.e., organic colors precipitated on alumina bases. Of the latter there are madder-lakes, prepared from madder-roots, and carmine-lakes, prepared from cochineal; of the former, vermillion (bisulphuret of mercury), Indian red (a native oxide of iron), Venetian red (also au oxide of iron), red lead (red oxide of lead or minium). A Very beautiful red is used by artists called palladium red; it is formed of ammonio-per chloride of palladium. Blurs consist of the artificial ultramarine, and for artists' pur poses of the real ultramarine, also the silicate of cobalt, and for water-colors, indigo and Prussian blue. Greens arc either produced by mixtures of yellows and /gum, or they are made directly from the phosphates, carbonates, acetates, and arsenites of copper, also from the sesquioxide of chromium and from terre rerte, a native mineral, consisting of iron, silica, potassa, and magnesia. The last two are the best for artists. Browns are numerous, and various in their composition. Decomposed peat, burned madder, burned Prussian blue, burned terre verte, asphalt, manganese brown, cateelm, umber (which is an oxide of iron with manganese), and mummy, or the asphalt mixed with other matters taken from Egyptian mummies, are amongst the best known and most used: Blacks are made of lampblack and bone-black (q.v.), peroxide of manganese, and blue-black, which is made of the charcoal of burned vine twigs.
in all cases the coloring materials of paints require to be very finely ground, and as many are very poisonous, great care is required in their preparation, and several forms of mill have been invented for the purpose. The principle upon which all are made is to secure the operator from the poisonous dust and exhalations, and to reduce the color ing material, if ground dry, to an impalpable powder, or, if mixed with the oil, to a perfectly smooth paste.