a well-known colour, supposed to be owing to the absence of light, most of the rays falling upon black substances being not reflected but absorbed by them. Concerning the peculiar structure of such bodies as fits them for appearing of this or that particular colour, see the article Colour.
Concerning black colours in general, we have the following remarks by Dr Lewis.
"1. Of black, as of other colours, there are many shades or varieties; different bodies, truly and simply black, or which have no sensible admixture of any of Commerce the rest of the colours, as black velvet, fine black cloth, of Art, the feathers of the raven, &c. appearing, when placed together, of teints very sensibly different.
"2. One and the same body also affumes different degrees of blackness, according to the disposition of the sensible part of its surface; and in this respect, there is not, perhaps, any other colour which is so much affected by an apparent mechanism. Thus black velvet, when the pile is raised, appears intensely black, much more so than the silk it was made from; but on pressing the pile smooth, it looks pale, and in certain positions shows somewhat even of a whitish cast.
"3. This observation is agreeable to the physical theory, which ascribes the blackness of bodies to the luminous..." luminous rays, that fall upon them, being in great part absorbed or stifled in their pores. When the surface is composed of a multitude of loose filaments, or small points, with the extremities turned towards the eye, much of the light is stifled in the interstices between them, and the body appears dark: when the filaments are pressed close, or the surface smoothed and polished, more of the light is reflected from it, and the intensity of the blackness is diminished; though the beauty may be improved by the glossiness which results from the smoothing.
4. There is one case, however, in which a high polish may, on the same principle, produce blackness, in bodies otherwise even white. We find that specula of white metal, or of quicksilvered glass, which reflect the rays of light to one point or in one direction, look always dark, unless when the eye is directly opposed to the reflected rays.
5. As the absorption of the luminous rays, except in the case just mentioned, makes the physical cause of blackness; it is concluded that black bodies receive heat more freely than others. Black marble or tiles, exposed to the sun, become sensibly hotter than white ones. Black paper is kindled by a burning glass much sooner than white, and the difference is strongly marked: a burning glass, too weak to have any visible effect at all upon white paper, shall readily kindle the same paper rubbed over with ink. Hence black clothes when wetted, are said to dry faster; black habits, and rooms hung with black, to be warmer; black mould to be a hotter foil for vegetables; and garden walls, painted black, to answer better for the ripening of wall-fruit than those of lighter colours.
6. It is not, however, to be affirmed that the like differences obtain in the impressions made by common fire. Black paper, held to the fire, does not seem to be affected sooner, or in a greater degree, than such as is white. It may be proper to observe also, that the combustibility of the paper may be increased, by impregnating it with substances of themselves not combustible, and which give no colour to it. This is the foundation of one of the sympathetic inks, as they are called, made of a strong solution of sal ammoniac in water, which, though colourless when written on paper, becomes very legible on exposing the paper to the fire; that is, it occasions the parts moistened with it to scorch or burn, before the rest of the paper is hurt, to a brown or black. All the salts I have tried produced this effect in a greater or less degree; nitre, alum, tartar, very weakly; sea-salt more strongly; fixed alkaline salts still more so; sal ammoniac the most strongly of all. Metallic solutions, made in acids, and diluted so as not to corrode the paper, acted in the same manner.
7. Besides the simple blacks, there are a multitude of compound ones, inclining more or less to other colours. Thus the painters have blue-blacks, brown-blacks, &c. which may be made by mixing pigments of the respective colours with simple black ones, in greater or less quantity, according to the shade required. The dyers also have different blacks, and often darken other colours by slightly passing them through the black dying liquor; but the term brown-black is in this business unknown, brown and black being here looked upon as opposite to one another. In effect, the colour called brown-black is no other than that which ill-died black clothes change to in wearing: no wonder then that it is excluded from the catalogue of the dyers colours.
8. The true or simple blacks, mixed with white, form different shades of gray, lighter or darker according as the white or black ingredients prevails in the mixt. The black pigments, spread thin upon a white ground, have a like effect.
9. Hence the painter, with one true black pigment, can produce on white paper, or on other white bodies, all the shades of grey and black, from the slightest discoloration of the paper up to a full black; and the dyer produces the same effect on white wool, silk, or cloth, by continuing the subjects for a shorter or longer time in the black bath, or making the bath itself weaker or stronger.
10. Hence also the dilution of black pigments with white, or the spreading of them thin upon a white ground, affords a ready method of judging of the quality or species of the colour; which if it be a true black, will in this diluted state look of a pure or simple grey; but if it has a tendency to any other colour, that colour will now betray itself.
11. All the colours in a very deep or concentrated state approach to blackness. Thus the red liquor prepared by boiling or infusing madder-root in water, and the yellow decoction or infusion of liquorice-root, evaporated in a gentle heat till they become thick, look of a dark black colour, or of a colour approaching to blackness; and these thick masses, drawn out into slender strings, or diluted with water, or rubbed on paper, exhibit again the red and yellow colours, which the liquors had at first. Nature affords many black objects, whose blackness depends upon the same principle, being truly a concentration of some of the other colours. Thus in black-berry, currants, elderberries, &c. what seems to be black is no other than an opaque deep red: their juice appears black when its surface is looked down upon in an opaque vessel, but red when diluted or spread thin. The black flint, as it is called, of the island of Ascension, held in thin pieces between the eye and the light, appears greenish; and one of the deep black stones called black agate, viewed in the same manner, discovers its true colour to be a deep red.
The most remarkable black colours in the mineral kingdom are, Black Chalk, Pit-Coal, Black Sands, and Black Lead (see these articles).—The only native vegetable black is the juice of the anacardium orientale; which possibly may be the tree that produces the excellent black varnish of China and Japan (see Varnish).—The juices of most astringent vegetables produce a black with iron, and for this purpose some of them are used in dyeing and calico-printing (see the article Dyeing).—There are also a number of black colours artificially prepared for the use of painters, such as lamp-black, ivory-black, German-black, &c. For an account of the preparation and qualities of which, see the article Colour-Making.
Black-Act: the statute of 9 Geo. I c. 22. is commonly called the Waltham black act, because it was occasioned by the devastations committed near Waltham in Essex, by persons disguised, or with their faces blacked. By this statute it is enacted, that persons hunting armed and disguised, and killing or stealing deer, or robbing Black-robbing warrens, or stealing fish out of any river, &c., or any persons unlawfully hunting in his majesty's forests, &c., or breaking down the head of any fish-pond, or killing, &c., of cattle, or cutting down trees, or setting fire to house, barn, or wood, or shooting at any person, or sending letters either anonymous or signed with a fictitious name demanding money, &c., or refusing such offenders, are guilty of felony, without benefit of clergy. This act is made perpetual by Geo. II. c. 42.
Black-Bird, in ornithology. See Turdus.
Black-Book of the Exchequer. See Exchequer.