Materials used in House-painting.
House-painting, in most cases, consists in laying on several coats of some mineral substances mixed up to a fluid consistence with oil. There is no other liquid body which is found to have so many advantages for this purpose as oil; for although turpentine, milk, beer, spirit, and other liquids are occasionally employed, oil is the standard material with which the colouring substances are mixed. The colouring substances, as well as the oils, employed in painting, are very numerous; and we can only offer a brief description of the principal among them.
White lead is the most valuable of all the colouring bodies, since it enters into the composition of almost every other. It is made by exposing sheet-lead to the action of vinegar, by which a white substance is procured. Bougival white, and Spanish white, are mineral substances procured from abroad. Chrome yellow, Turner’s yellow, Massicot, Naples yellow, King’s yellow, Orpiment, and Ochres, are various bodies of a yellow colour, some derived from earths, others from ores, and others from chemical treatment of metals. Vermilion, Carmine, Cochineal lake, Madder lake, Red lead, Indian red, Venetian red, &c., produce various tints of red and crimson; but the materials themselves are derived from very different sources. Vermilion is a compound of sulphur and mercury; Carmine and Cochineal lake are prepared from an animal substance; Madder lake from a vegetable; Red lead is an oxide of that metal; while the others are derived from various kinds of earth. For a blue colour, the painter employs Prussian blue, which is a compound of prussic acid and iron; Indigo, derived from a plant growing in the East Indies; Blue Verditer, a nitrate of copper; and some other substances. Most green paints are made of salts of copper, such as Verdigris, which is an acetate of copper; Scheele’s green, an arseniate of copper; Green Verditer, a nitrate of copper, and Brunswick green, a muriate of copper; together with two or three earths, such as Italian green, Saxon green, &c. Browns are generally produced by a mixture of black and red; but there are several earths which yield a brown colour. These are the principal colouring materials employed by the house-painter, for almost every intermediate tint or grade of colour can be produced by mixtures of two or more of the above-mentioned materials, in certain proportions.
The liquid principally employed to mix with these dry colours is Linseed oil. This is obtained by beating, pressing, or heating, from the seed of the flax plant, the Linum usitatissimum, which grows in most parts of Europe. This oil has so much fatness or unctuousness, that it would dry with extreme slowness were not some further precautions taken. It is boiled with litharge and white vitriol, in certain proportions, by which it has a drying quality imparted to it. Nut oil is sometimes used in painting: this is procured from the kernels of walnuts, beech nuts, hazel nuts, and other kinds of nut, by a process similar to that by which linseed oil is obtained. Oil of turpentine, or turps, is largely used by painters, as it has a drying quality which counteracts the fatty nature of linseed oil, in combination with which it is generally used. It is obtained from a liquid or sap exuding from a species of pine tree, in North America: the sap is crude, or common turpentine; and by a process of distillation, the oil of turpentine is obtained from it, leaving a substance behind which constitutes yellow resin. Oil of spike, oil of lavender, and oil of poppies, are sometimes used by the painter; but not very frequently, on account of their expense; they are vegetable preparations. Pilchard oil, (obtained from the fish,) common tar, coal tar, and oil of tar, are used occasionally for rough exterior work. Varnish, size, beer, milk, and one or two other liquids are used to a small extent in some processes to which the painter has to direct his attention. Varnishes are mixtures of various resinous bodies with spirit; and size is a jelly obtained by boiling parchment, leather, parings of hoofs, or of horn, or some similar animal substance, in water.