CRAYON, a coloured material for drawing, employed generally in the form of pencils, but sometimes also as a powder, and consisting of native earthy and stony friable substances, or of artificially prepared mixtures of a base uf pipe or China clay with Prussian blue, orpiment vermilion, umber, and other pigments. Calcined gypsum, talc, and compounds of magnesium, bismuth, and lead are occasionally used as bases. The required shades of tints are obtained by adding varying amounts of colouring matter to equal quantities of the base. The ingredients of crayons or pastils are made into a paste with gum, turpentine, or alcoholic solution of shellac, and pιdverized as finely as possible in a mill, which subjects them repeatedly to the action of a revolving cast-iron grinder. The paste is introduced into a copper cylinder, closed at one end by a plate pierced with holes of the diameter of the. crayons to be made. Through these it is forced by means of a piston, and the vermicular pieces obtained are then cut into the required lengths, and dried in a furnace at a gentle heat. Black crayons may be manufactured from a mixture of one part of lamp-black with about two-thirds of its bulk of clay; red crayons from powdered and elutriated haematite worked up into a paste with gum arabic and a little soap. White crayons are commonly formed by sawing chalk of good quality into convenient shapes. Mixtures of soap, wax, and lampblack are employed for lithographic crayons or chalks. The late well-known zoological lithographer, George Ford, employed chalks made after the following receipt :— [table]...
The wax is gradually incorporated with the melted soap by heating, and as the resultant mass begins to burn, the soda is added; afterwards the black is by degrees stirred in. The melted tallow may be added at any stage in the operation.
Crayons are valuable to the artist in enabling him to make groupings of colours and to secure landscape and other effects with ease and rapidity. The outline as well as the rest of the picture is drawn in crayon. The colours are softened off and blended by the finger, with the assistance of a stump of leather or paper; and shading is produced by cross-hatching and stippling. The paper employed is of loose but not soft or spongy texture, and is of various tints, warm grey or yellowish being generally preferred. For portraits pumice-paper and red or brown crayons are considered most suitable. The colours are fixed by the process known as transudation. The drawing is supported face downwards by its edges or corners, and a solution of isinglass is applied to the back with a brush in quantity sufficient to penetrate to the coloured surface of the paper, which may then be turned upwards to dry. The fixing solution is prepared as follows;—three-quarters of an ounce of isinglass is infused for a day in 2⅜ ounce of pure vinegar; a pint of hot water is added, and the solution of isinρ∙bss is filtered and mixed with an equal volume of spirits of wine, The art of painting in crayons or pastils is supposed to have originated in Germany in the 17th century. By Johann Alexander Thiele (1685-1752) it was carried to great perfection, and in France it was early practised with much success. Amongst celebrated crayon-painters may be mentioned Carriera Rosalba (1675-1757), W. Hoare (1707-1792), F. Cotes (1726-1770), J. Russell (1744-1806), and the late Mr Bright.
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