6. Pale shell-lac, 5 parts; wood naphtha, 12 parts; dissolve, and with this fluid mix up the colouring powder, previously stirred up with an equal weight of fine pale-blue clay; dry by a stove heat, as before. When this process is well managed, it produces crayons equal to those of the best Parisian houses.
Obs. The composition may be formed into crayons by simply rolling it on a slab; but to ensure their solidity the manufacturers generally employ a metallic cylinder of 2 or 3 inches in diameter, with one end open and the other firmly secured to a perforated plate, having holes of the same size as the intended crayons. The crayon composition, in the state of a stiff paste or dough, is introduced into the open end, and is forced down and through the holes, by means of a small plug or piston, that exactly fits the inside of the cylinder, and which is driven by the equable motion of a small screw. The pieces that pass through the holes are then cut into lengths and dried.
The substances employed as colouring matters for crayons are very numerous, and their choice offers a wide field for the skill and fancy of the artist. The pigment having been selected, it may be reduced to any shade or tint by admixture with other pigments, and by ‘dilution’ with a proper quantity of elutriated or prepared chalk. As, however, crayon colours do not admit of being mixed together at the time of using them, like liquid colours, it is usual to make 3 to 6 different shades of each colour, so as to enable the artist at once to produce any effect he chooses.
Crayons, Black. From prepared black-lead, ivory-black, lamp-black, &c. Black chalk and charcoal are frequently made into crayons by simply sawing them into suitably sized pieces. They may then be put into a pipkin of melted wax, and allowed to macerate for an hour; after which they should be taken out, drained, and laid on a piece of blotting paper to dry. Drawings made with these crayons are very permanent, and if warmed slightly on the wrong side, the lines will adhere, and become almost as durable as ink.
Crayons, Blue. From indigo, smalts, Prussian blue, verditer, &c.
Crayons, Brown. From umber (raw and burnt), terra di Sienna (raw and burnt), Cullen’s earth, brown ochre, &c.; and some peculiar shades, from a mixture of black, carmine, and either of the above colours.
Crayons, Green. From a mixture of king’s yellow, or yellow ochre, with blues.
Crayons, Purple. From any of the more brilliant blues, mixed with carmine, lake, or vermilion.
Crayons, Red. From carmine, carminated lakes, vermilion, hematite, and any of the earthy or mineral colours commonly used as pigments. Crayons of red chalk may be prepared in the manner pointed out for crayons of black chalk.
Crayons, White. From pure clay and chalk.