Photo-Lithography

4 The Greasy Drawing Materials

which are necessary for lithography are litho tusch, autographic ink, and fatty chalk.

The two first are used in the liquid state, the chalk, however, in solid form. The ink can be obtained in a liquid form and the two others in solid state. All three materials consist principally of soap, tallow, wax, resin, and soot. Soap and tallow give the necessary grease, wax and resin give hardness and consistency, and soot the colour. The proportion of grease in the drawing materials must be so great that even the finest lines or points of a drawing can be well transferred to the stone, so that they may not be attacked by the proper etching solution, and do not break away from the stone by continuous printing. As much black as possible in the drawing materials is pleasant for the draughtsman, but is not actually necessary for this particular purpose.

The tusch must dissolve well in distilled water and flow fine and clean from the pen. It should be tolerably brittle, and the fractured surfaces should be shiny. The photo-lithographer will frequently require the lithographic tusch for additions or for corrections. The best is the so-called Lemercier’s tusch, which is used in nearly all works. It consists of—

Yellow wax	2	parts
Mutton tallow	2	parts
Marseilles soap	6	parts
Shellac	3	parts
Lamp black	1–2	parts

These ingredients should be melted together by boiling.

The autographic ink is, as a rule, used for drawing or writing on paper, and the result is then transferred to the stone. Instead of this, any litho tusch can be used, but for some work the autographic ink is more advantageous. This ink must be thin, run easily, but not patchily, from the pen, and must keep for a long time equal in quality and action. It is very advantageous that specially-prepared paper is not required, since this always makes the work more difficult; firm, hard writing-paper is quite good enough for this work. The commercial inks generally possess these good qualities, and if much is not required one will hardly care to prepare it oneself. A good successful autographic ink which draws in brown may be obtained from the following formula:—

Marseilles soap	10	parts
Tallow	10	parts
Shellac	12	parts
Yellow wax	12	parts
Mastic	5	parts
Asphalt	4	parts
Vine soot	3	parts
Distilled water	125	parts

Originals prepared with this ink transfer as well immediately as after several months, and ordinary well-sized writing paper can be used for drawing or writing on.

Lithographic chalk is only prepared in the solid form for drawing on paper direct or on stone. According to the nature of the work, it is harder or softer, fatter or leaner. The hard kinds, which are also usually leaner, contain more resin and less fat; the soft, on the contrary, more grease.

Fatty chalk is composed of—

Wax	30	parts.
Marseilles soap	24	parts.
Tallow	4	parts.
Shellac	1	part.
Lampblack	6	parts.

Lean chalk is composed of—

Wax	12	parts.
Marseilles soap	8	parts.
Tallow	2	parts.
Shellac	10	parts.
Lampblack	4	parts.

For lithographic work a greasy ink is required in contra­dis­tinc­tion to ordinary printing ink, which consists of linseed oil and lamp­black, which would be called “lean.” For inking-up a photo-lith­o­graphic chromated gelatine print such an ink cannot be used. In order to obtain a good result in trans­ferring, this ink must contain grease, soap, and resin.

Any good transfer ink can be used for a developing ink, as this is applied with a roller. It usually consists of equal parts of tallow, wax, soap, some resin, and as much litho ink as all the other ingredients put together.

That prepared by C. Kampmann, Technical Instructor in the K.K. Lehr-und Versuchsanstalt at Vienna, contains, besides the above-named ingredients, asphalt and gum elemi, and works well in practice.

Thin developing inks, which are distributed with a broad brush or a pad, can be prepared by diluting good transfer ink with equal quantities of wax, benzine, and turpentine.

A good developing ink must have the following properties: When spread upon the print must give a clean, sharp, sufficiently dense impression, which can be easily transferred to the plate or stone; on the other hand, the drawing ought not to spread. The transfer should possess such resistance that, without rolling up, it should resist a slight etching.