The tendency in the compounds of colours to run into brownness and warmth is one of the common natural properties of colours which occasions them to deteriorate or defile each other in mixture. Brown by consequence is synonymous with foul or dirty, as opposed to fair or clean; and hence brown, which is the nearest of the semi-neutrals in relation to light, is to be avoided in mixture with light colours. Yet is it an example of the wisdom of nature's Author that brown is rendered, like green, a prevailing hue, and in particular an earth colour, as a contrast which is harmonized by the blueness and coldness of the sky.
This tendency will likewise explain the use of brown in harmonizing and toning, as well as the great number of natural and artificial pigments and colours so called. It was the fertility and abundance of browns that caused our great landscape-colourist Wilson, when a friend went exultingly to tell him that he had discovered a new brown, to check him in his characteristic way, with—"I'm sorry for it: we have gotten too many of them already." Nevertheless, fine transparent browns are obviously very valuable.
If red or blue in excess be added to brown, it falls into the other semi-neutral classes, marrone or gray. The wide acceptation of the term brown has occasioned much confusion in the naming of colours, since broken colours in which red, &c. predominate, have been improperly called brown. That term, therefore, should be confined to the semi-neutral colours, compounded of, or like in hue to, either the primary yellow, the secondary orange, or the tertiary citrine, with a black. The general contrast or harmonizing colour of such compounds will consequently be more or less purple or blue.
The number of browns is great, as may be seen by the following list. This list, however, is good, and includes a considerable proportion of permanent pigments.
241. ASPHALTUM,
Asphalt, Bitumen, Mineral Pitch, Jew's Pitch, Antwerp Brown, Liquid Asphaltum, &c., is a sort of mineral pitch or tar which, rising liquid to the surface of the Lacus Asphaltites or Asphaltic Lake (the Dead Sea) concretes there by the natural action of the atmosphere and sun, and, floating in masses to the shores, is gathered by the Arabs. The French give it an additional name from the region of the lake, to wit, Bitumen of Judea; and with the English, from the same cause, it has the alias of Jew's pitch. Asphaltum is not so called, however, after the lake, as is asserted by a writer in the Encyclopædia: it is just the reverse—Pliny says, "The Asphaltic lake produces nothing but bitumen (in Greek, asphaltos); and hence its name."
A substance resembling asphalt is found at Neufchâtel in Switzerland, and in other parts of Europe. A specimen of the native bitumen, brought from Persia, and of which the author made trial, had a powerful scent of garlic when rubbed. In the fire it softened without flowing, and burnt with a lambent flame; did not dissolve by heat in turpentine, but ground easily as a pigment in pale drying oil, affording a fine deep transparent brown colour, resembling that of commercial asphaltum; dried firmly almost as soon as the drying-oil alone, and worked admirably both in water and oil. Asphaltum may be used as a permanent brown in water, for which purpose the native is superior to the artificial. The former, however, is now seldom to be met with, the varieties employed on the palette being the residua of various resinous and bituminous matters, distilled for the sake of their essential oils. These residua are all black and glossy like common pitch, which differs from them only in having been less acted upon by fire, and thence in being softer. At present asphaltum is prepared in excessive abundance as a product of the distillation of coal at the gas manufactories, and is chiefly confined to oil-painting, being first dissolved in turpentine, which fits it for glazing and shading. Its fine brown colour and perfect transparency are lures to its free use with many artists, notwithstanding the certain destruction that awaits the work on which it is much employed, owing to its tendency to contract and crack by changes of temperature and the atmosphere; but for which, and a slight liability to blacken, it would be a most beautiful, durable, and eligible pigment. The solution of asphaltum in turpentine, united with drying oil by heat, or the bitumen torrefied and ground in linseed or drying-oil, acquires a firmer texture, but becomes less transparent and dries with difficulty. If common asphaltum, as usually prepared with turpentine, be used with some addition of Vandyke brown, umber, or Cappah brown ground in drying oil, it will gain body and solidity which will render it much less disposed to crack. Nevertheless, asphaltum is to be regarded in practice rather as a dark varnish than as a solid pigment, and all the faults of a bad varnish are to be guarded against in employing it.
It is common to call the solution in turpentine Asphaltum, and the mixture with drying-oil Bitumen: the latter is likewise known as Antwerp Brown. A preparation for the use of water-colour artists is employed under the name of Liquid Asphaltum.
242. BISTRE
is extracted by watery solution from the soot of wood fires, whence it derives a strong pyroligneous scent. It is a very powerful citrine-brown, washes well, and has a clearness suited to architectural subjects. Its use is confined to water-colour painting, in which it was much employed by the old masters for tinting drawings and shading sketches, before the general application of Indian ink to such purposes. Of a wax-like texture, it is perfectly durable, but unfitted for oil, drying therein with the greatest difficulty.