Pencil and chalk drawings, assuming that they are cleanly executed, can be well reproduced by photo-lithography, only they ought not to be smudged or inked. Erasure marks on pencil drawings appear in the reproduction as smudgy spots.
Drawings of architecture for illustration or other purposes, after consideration of these remarks, can be well transferred without much trouble by photo-lithography on to stone or zinc.
In drawings of maps, plans, etc., there are still some rules to be observed besides the above. Boundary lines or mountain ranges with fine hatching, waterlines for large rivers, seas or lakes, as well as the introduction of figures, are better left out of the drawing, and can be afterwards drawn on the stone; they will then be cleaner and sharper. If all these details, however, must be introduced into the original drawing, they should be executed in a pale blue colour, which will not appear in the ordinary negative.
For plans with large letters it is better not to draw the latter, which are frequently a lot of trouble, but to employ the simpler plan of getting the titles, writing, legends, explanations, etc., printed by a book printer on paper of the same colour as the original, and stick them on the latter. The same method may be {23} adopted when preparing railway, postal, and telegraphic charts or maps with a lot of names or other titles, etc. The network of lines may be drawn with litho ink as suggested above, but the names of the stations, etc., can be printed with letterpress and stuck on in the proper places. Working in this way not only will much labour be saved, but at the same time sharper and more correct titles be obtained on the reproduction.
Any necessary instructions for carrying out the drawing should never be made on the paper with red pencil, but either with pale grey or pale blue. For this paper rubbed with indigo or graphite can be used or a scratched gelatine proof which has been rubbed with finely powdered milori blue.
With commercial drawings it frequently happens that ornaments are repeated. It is not necessary for the designer to draw all the ornamentation, which may frequently be very complicated, if it runs over the whole of the design. It is quite sufficient, according to the size or the number of times that the ornament occurs, for the artist to draw it twice or three times, or sometimes ten to fifteen times; the lithographer will duplicate it by transfer. This also applies if there is a border, or if there are any corner or centre pieces repeatedly used. It is quite sufficient to draw one-fourth of the frame or border, or with very complicated designs a complete corner, and to give the printer a rough sketch of the complete border. He will make the necessary impression on transfer paper by photo-litho transfer on the stone; he will also reverse the drawing from right to left, join up the different parts, and thus construct the whole border. This applies also to the corner and centre piece.
(B.) DRAWINGS ON BLUE PRINTS.
As a substitute for a proof cyanotype or blue prints may be used for preparing drawings for photo-lithography and other graphic arts. When a photo-lithograph like a pen and ink drawing is to be prepared from a coloured picture, or from a sepia or Indian ink wash drawing of a plastic object or a photograph from nature, or from an object not suitable for photographic reproduction an autotypic transfer is to be prepared, a proof of the desired object must be first prepared, and then from this the drawing is to be made. It is obvious that the proofs of the first-named can only be made in the original size, which under some circumstances may not be just what is required, assuming that the original can be used in this way. In all cases this will be inconvenient and tedious, and possibly from the nature of the drawing many proofs be lost. The end will be attained far more quickly and safely if a negative is made of the original, either of the same size or enlarged according as may be desired. The negative thus obtained is used to make a ferro-prussiate print. {24} For this we use a good firm drawing paper, which is sensitized in the following mixture:—
Solution A. | ||
Potassium ferridcyanide | 8 | parts. |
Water | 150 | parts. |
Solution B. | ||
Ammonio-citrate of iron | 10 | parts. |
Water | 100 | parts. |
When dissolved each solution is filtered and mixed in the dark room immediately before use in equal parts. The solution thus formed is sensitive to light and is spread on a well-sized drawing paper as evenly as possible with a broad brush, equalized with a distributing brush, and then dried in the dark room.