thereby rendered insoluble. The heat should not exceed 430°, nor be less than about 400° Fahr. The process, for nice experiments, is best conducted in a bath of melted tin, to which a little bismuth has been added to reduce its melting-point to about 435°; a little powdered resin or charcoal or a little oil being put upon the surface of the metal, to prevent the oxidisement of the alloy. See Caramel.
COL′OURS. White light from the sun is of a compound nature, and may be decomposed into rays of different colours. Newton distinguished seven PRIMITIVE COLOURS, namely, violet, indigo, blue, green, yellow, orange, and red. Sir D. Brewster is disposed to think that four of these colours are really compound, and that three, namely, blue, yellow, and red, alone deserve the name of primitive. The colours of natural objects are supposed to result from the power possessed by their surfaces of absorbing some of the coloured rays of light, while they reflect or transmit, as the case may be, the remainder of the rays. Thus, an object appears red because it absorbs or causes to disappear the yellow and blue rays composing the white light by which it is illuminated. Black and white are not colours, strictly speaking.
A body is said to be black when it absorbs or quenches a large proportion of all the rays of white light falling upon it. A body is said to be white when it receives the white light, and reflects all the rays with moderate strength. Grey may be regarded as a luminous black or dark white. The names given to colours are far from being satisfactory, for although many thousand shades may be distinguished by a practised eye, it is a question whether there are fifty names which would convey the same idea of shade to any ten colourists in the world. The names taken from natural coloured objects, as indigo, violet, orange, lilac, amber, emerald, &c., are the least objectionable. M. Chevreul has devised an ingenious system of naming and classifying colours. He employs only 6 fundamental names, which are those of the three elementary colours, red, yellow, and blue; and of the three secondary colours, orange, green, and violet. By the direct union of the elementary and secondary colours, 6 tertiary colours are formed. He arranges the twelve colours in a circle, like the spokes of a wheel, commencing with the red, and going to the right, thus:—Red, red-orange, orange, yellow-orange, yellow, yellow-green, green, blue-green, blue, blue-violet, violet, red-violet. The chromatic circle is completed by placing 5 shades between the red and red-orange, 5 between the red-orange and orange; and so on between each of the other couples. This chromatic circle of 72 colours is not imaginary, but actually exists, composed of dyed wools. The shades are distinguished by numbers; thus there are red, 1 red, 2 red, 3 red, 4 red, and 5 red, &c. Each of the 72 shades has, moreover, 20 different degrees of depth, from the lightest that can be discerned from pure white to the most intense depth, approaching to brown and black. These degrees of depth are called tones or tints. The addition of these tones to the chromatic circle brings up the number of tints to 1440. To indicate any one of these tints we have merely to write the number of the shade, and after it the number of the tone, as, for example, 3 blue-violet, 13 tone. By mixing each of the 1440 tints with grey or black, so as to darken it in different degrees, a total of 14,440 colours may be defined. This part of the system is generally regarded as unnecessary. Mr O′Neill, in his valuable ‘Dictionary of Calico Printing and Dyeing’ (to which work we refer the reader for a full account of Chevreul’s classification), gives a long list of colours and coloured bodies, which are pretty well defined in common language with the names of the colours, according to this ingenious system. We select from this list the following examples:—
Amber in mass = 2 orange, 12 tone. Amethyst = 5 blue-violet, from 3 to 16 tone. Blood, ox = 1 red, 13 and 14 tones. Butter = yellow-orange, 2 to 3 tone. Carrot = orange, 7 tone. Chocolate in cake = 5 orange, 18 tone. Emerald = 2 green, 11 tone. Green, apple = 4 yellow-green, 8 tone. Isabelle = 1 yellow-orange. Mauve = 3 violet, 8 tone. Red-lead = yellow-orange, 20 tone. Ruby = red, 11 tone. Yellow, canary = 1 yellow, 6 tone.
For notices of Dyes, Pigments, &c., refer to the principal colours.
Colours, Cake. Syn. Artists’ Colours. These are made by grinding by means of a glass muller and a slab, the respective pigments previously reduced to powder, into a smooth paste with equal parts of isinglass size, and thin gum water. The paste is then compressed into squares as tightly as possible, and dried with a very gentle heat. Old crumbling cake colours should be powdered very finely in a biscuit-ware mortar, sifted through fine muslin, and ground up as above, the gum water being omitted. The powders rubbed up with honey to the consistence of cream constitute moist colours.
Colours, Complement′ary. Syn. Accident′al Colours. Colours are said to be complementary to each other which, by blending together, produce the perception of whiteness. According to Mayer, all colours are produced by the admixture of red, yellow, and blue light, in certain proportions; and by intercepting either one or more of these coloured rays in a beam of light, those which meet the eye will consist of the remaining coloured rays of the spectrum. Thus, by intercepting the red rays in a beam of white light, the remaining yellow and blue rays will produce a
green colour; by intercepting the blue rays, the remaining yellow and red will give an orange; and so on of other cases; so that red and green, blue and orange, are COMPLEMENTARY COLOURS. If we look for some time, with one eye, on a bright-coloured object, as a wafer, placed on a piece of paper, and subsequently turn the same eye to another part of the paper, a similarly shaped spot or mark will be seen, but the colour will vary, though it will be always the same under like circumstances. Thus, if the original spot or wafer be of a red colour, the imaginary one will be green; if black, it will be white; the imaginary colour being always complementary of that first gazed upon. The colour so perceived is often called an ACCIDENTAL COLOUR, to distinguish it from the real colour. It is a general maxim in design that “colours look brightest when near their complementary colours.”
Colours, Drug′gists’ Show. See Show Bottles.
Colours, Flame. See Fires (Coloured).