COLOURS. The word Colour is used in many different ways. Besides its original meaning, in relation to the tints of rays of light, it has gradually come to be applied to the substances by which those tints are imi tated.
Painter's Colours, for house-painting and similar purposes, are mostly prepared from mineral substances (white lead, red lead, um ber, ochre, Rze.) ground up with linseed oil and turpentine to the state of a thick liquid. It would, perhaps, scarcely he supposed that Painters' Colours' appear in the Board of Trade tables, as an article of export to the value of about 170,0001. annually.
The oil colours for artists are more carefully prepared than those for house painting. They used to be sold tied up in small bladders ; but an ingenious and more convenient arrange meut is now adopted. Mr. Winsor's envelopes for colours, patented in 1840, consist of small metal or glass tubes, open at both ends, and provided with elastic pistons or plugs of cork or some similar material. The piston has a worm or nut in its centre, which corresponds to a screw attached to a handle rather larger than the tube. The open ends of the tube are covered with small metallic plates having holes in their centres. When the colour is placed in the tube, the arrangement of the apparatus is such as to keep the air from acting on it ; and when any is required to be used, the screw is turned round,the piston is pressed down and a little colour exudes from the lower end.Mr. Rand'sColiapsibleColour-tubes, so useful to ar tists, were the subject of a later patent in 1842 ; the objects of which were, to introduce a mode of punching out by dies the thin pieces of tin of which the tubes are made ; and to make a screw cap at the mouth of the tube, to prevent leakage. These little tubes, by a gentle
squeeze, arc made to yield the colour at one end just in sufficient quantity for use.
Water-Colours for artists include both vege table and animal as well as mineral substances, and are prepared with very great care.
Mr. Smith of Blackford has lately commu nicated to the Royal Scottish Society of Arts, a paper showing that when chromate of lead is mixed with muriate of ammonia, and sub jected to the action of heat, a substance is ob tained of a different colour from either of the matters used. If the proportions of the sub stances be varied, and different degrees of heat applied, distinct colours and tints will be the result. Thus, when five parts of chromate of lead, and one part of muriate of ammonia, are heated to redness in a crucible, a red colour is obtained ; a blue colour is formed by heating 10 parts of muriate of ammonia, and 1 part of chromate of lead to ebullition ; and a green is produced when the last mixture is heated nearly to redness. By employing various pro portions of the substances, and different de grees of heat, a great variety of tints are formed—scarlets, oranges, browns, blues, pu• ples, greens, yellows, and others. It is con ceived that these properties may lead to use ful applications in the arts.