Lithographic crayons

—Fine lithographic prints cannot be obtained unle the crayons po e every requisite quality. The ingredients composing them ought to be of such a nature as to adhere strongly to the stone, both after the drawing has undergone the preparation of the acid, and during the pre -work. They should be hard enough to admit of a fine point, and trace delicate lines without risk of breaking. The following composition has been succe fully employed for crayons by MM. Bernard and Delarue, at Paris :— | Pure wax, (first quality) | 4 | | Dry white tallow soap | 2 | | White tallow | 2 | | Gum lac | 2 | | Lamp black, enough to give a dark tint | 1 | | Occasionally copal varnish | 1 | The wax is to be melted over a gentle fire, and the lac broken to bits is then to be added by degrees, stirring all the while with a spatula; the soap is next introduced in fine shavings; and when the mixture of these substances is very intimately accomplished, the copal-varnish, incorporated with the lamp black, is poured in. The heat and agitation are continued till the paste has acquired a suitable consistence; which may be recognised by taking out a little of it, letting it cool on a plate, and trying its quality with a penknife. This composition, on being cut, should afford brittle slices. The boiling may be quickened by setting the rising vapours on fire, which increases the temperature, and renders the exhalations le offensive. When ready, it is to be poured into a bra mould, made of two semi-cylinders joined together by clasps or rings, forming between them a cylindric tube of the crayon size. The mould should be previously smeared with a greasy cloth. M. Last eyrie prescribes a more simple composition, said to be equally fit for the lithographer’s use :— | Dried white tallow soap | 6 | parts. | | White wax | 6 | — | | Lamp black | 1 | — | The soap and tallow are to be put into a small goblet and covered up. When the whole is thoroughly fused by heat, and no clots remain, the black is gradually sprinkled in with careful stirring. Lithographic ink is prepared nearly on the same principles :— | Wax | 16 | parts. | | Tallow | 6 | — | | Hard tallow soap | 6 | — | | Shell-lac | 12 | — | | Mastic in tears | 8 | — | | Venice turpentine | 1 | — | | Lamp black | 4 | — | The mastic and lac, previously ground together, are to be heated with care in the turpentine; the wax and tallow are to be added after they are taken off the fire, and when their solution is effected, the soap shavings are to be thrown in. Lastly, the lamp black is to be well intermixed. Whenever the union is accomplished by heat, the operation is finished; the liquor is left to cool a little, then poured out on tables, and, when cold, cut into square rods. Lithographic ink of good quality ought to be susceptible of forming an emulsion so attenuated, that it may appear to be di olved when rubbed upon a hard body in distilled or river water. It should be flowing in the pen, not spreading on the stone; capable of forming delicate traces, and very black to show its delineations. The most e ential quality of the ink is to sink well into the stone, so as to re-produce the most delicate outlines of the drawing, and to afford a great many impre ions. It must therefore be able to resist the acid with which the stone is moistened in the preparation, without letting any of its greasy matter escape. M. de Last eyrie states that after having tried a great many combinations, he gives the preference to the following :— | Tallow soap, dried | 30 | parts. | | Mastic, in tears | 30 | — | | White soda of commerce | 30 | — | | Shell-lac | 150 | — | | Lamp black | 12 | — | The soap is first put into the goblet and melted over the fire, to which the lac being added fuses immediately; the soda is then introduced, and next the mastic, stirring all the while with a spatula. A brisk fire is applied till all these materials be melted completely, when the whole is poured out into the mould. The inks now prescribed may be employed equally with the pen and the hair pencil, for writings, black-lead drawings, aqua tint a , mixed drawings, those which represent engravings on wood (wood cuts), . When the ink is to be used it is to be rubbed down with water, in the manner of China ink, till the shade be of the requisite depth. The temperature of the place ought to be from 84° to 90° Fahr., or the saucer in which the ink-stick is rubbed should be set in a heated plate. No more ink should be di olved than is to be used at the time, for it rarely keeps in the liquid state for 24 hours; and it should be covered or corked up.