CHAPTER XXI

THE VARIOUS METHODS OF REPRODUCTION

It is essential that the artist who does work for reproduction should have some knowledge of the different methods employed. A lack of knowledge in this respect is responsible for a large number of drawings made which are quite unsuitable for the purpose. It is not necessary that the student should be able to reproduce his own work by the various methods used, but he should be familiar, in a slight degree, with the processes used.

For black-and-white work, the two processes largely used by publishers in magazines, etc., are known as Line Process and Half-Tone. The former is used for the reproduction of pen-drawings, and the latter for tone drawings.

The line process is the most useful for the class of work that the illuminator is likely to do. In this case the method of procedure is briefly as follows: The drawing is made with good black ink on white paper. It is then photographed. A piece of polished zinc is given a thin film of fish-glue in which some bichromate of potash has been dissolved. The effect of the bichromate is to make the fish-glue insoluble when it has been exposed to the light. The zinc plate is dried rapidly in a subdued light, and is then exposed behind the negative. The light, penetrating through the clear parts of the negative, renders these insoluble. The zinc is then given a thin coating of soft, greasy ink with a roller. It is then placed in a dish of water to develop. The effect of the water is to dissolve the fish-glue that has been protected, and is therefore still soluble. This leaves the design on the surface of the zinc in ink. While the ink is still tacky, it is dusted over with resin. This is fused over a stove, and the background of the zinc is etched away in an acid bath, leaving the design standing in relief.

This is, briefly, an outline of the process of making a line block. Of course, it must be understood that many details are omitted in this description. These, however, although most important to the block-maker, are not necessarily essential to the artist. The chief thing that he should be careful to ensure is that his drawings should be executed with an absolutely black line on white paper. By this means he will have done his part to help the block-maker to obtain a clear negative, which is unquestionably vital to the production of a successful process block. Drawings executed with a weak, washy kind of ink on yellow-toned paper do not give the block-maker a chance. The thing, then, for the artist to remember is to see that his drawing consists of firm black lines on a white surface, with no half-tones, unless these are produced by means of lines.

For drawings executed in tone, the other method, known as the half-tone process, is used. In this case the drawing is photographed with a glass screen in front of the negative. This screen is ruled with fine lines in such a manner that the tints of the original are broken up into dots. The print is obtained on the metal, and the block is made in a somewhat similar manner to that of a line block. In etching, the metal is bitten away round the edges of the various dots more or less, according to the strength of these. This gives a similar effect of light and shade to the original. An examination, with a magnifying-glass, of any reproduction of a photograph or tone-drawing in any of the magazines of the present day will show this quite plainly.

When working for this process, drawings should be rather more vigorous than are required in the finished production. The reason for this is that the photograph generally softens down everything, so it is as well to forestall this by making the original stronger.

It is also important that the half-tones in the drawing should not tend towards being a bluish grey, as blue does not photograph well. The result of a reproduction from a drawing of this kind would be that the half-tones would be much weaker than in the original.

In colour reproduction, a method largely used is that known as the three-colour process. This is a development of the half-tone process. In this case, however, the drawing is photographed three times in succession on different plates. In each case a colour filter is placed in front of the lens, which allows only the red, yellow, or blue rays to pass through. By this means the three negatives obtained are records of the red, yellow, and blue used in the drawing. Three blocks are made, and are printed in red, yellow, and blue ink respectively, superimposed over each other. This, if carefully done, gives a fairly faithful reproduction of the original. Sometimes an extra block is used, and in the case of the reproduction of illuminated work, a special block is used to print the gold. It can easily be understood why this is necessary, as, when printed from the three blocks only, this comes out as a colour in the printing.

When working for this form of reproduction there is no need to limit oneself in the number of colours used. Work that has been executed with about twenty different colours can be reproduced as easily as that in which only four or five colours are used.

As in half-tone, the work should be stronger and more vigorous than is needed in the finished reproduction. The colours also should be bright and clear, and the modelling should be strongly accentuated, as this process has a tendency towards flattening everything. If the original appears flat and washed-out in treatment, it will certainly look much worse when reproduced.

Another process, largely used for commercial work, is lithography. This is quite different from any of the previously mentioned processes. In all these the blocks are in relief, and are printed in a typographic press. For the general form of lithography, a species of limestone is used. This process depends on the absorption of grease by this stone, and on the mutual antipathy of grease and water. The design is drawn on the surface of the stone with a greasy ink. The grease is absorbed by the stone. The stone is then damped all over; the greasy ink of the design repels the water, but where there is no design the surface of the stone becomes wet. An ink-roller is then passed over the stone while it is still damp. As this printing ink is of a greasy nature, it will leave the roller only for the lines of the design, which remain quite dry. The moist surface of the stone repels the ink. After the stone has been inked up, a print is obtained in a lithographic press.

For general work the surface of the stone is highly polished, but for the reproduction of chalk drawings and for shading purposes it is given a grain.

Zinc and aluminium plates are often used as substitutes for stone. These, although not as good as stone, have the advantages of being cheaper and more portable.

Colour printing by this process is known as chromo-lithography. A separate stone is used to print each colour. A careful tracing is first made of the outline of the drawing, and this is transferred to the surface of the stone. This forms the key-stone from which the other colour stones are prepared. When it is desired to print gold, the stone is rolled up with a very sticky kind of ink. A print is obtained in this medium, and while this is still tacky it is dusted over with powdered bronze, which adheres to the print and gives the effect of gilding to some extent. For very special work real gold is occasionally employed instead of bronze powder.

It can easily be understood that the larger number of colours used, the more costly this process is. Students often wonder why designs are sometimes not accepted by firms who use this process. Very often one of the most important reasons is that too many colours are employed. If a design is shown that can be produced with a striking effect with two or three printings only, it will certainly be considered before one requiring ten or twelve.

Lithography is used for the greater bulk of commercial work, such as posters, labels, Christmas cards, etc.

The great thing to remember when doing work for reproduction by chromo-lithography is to get a good effect with as few colours as possible. There is no need in this case to make the drawing more vigorous than is required, as the lithographer will endeavour to get exactly the same effect as in the original.

The student who is ignorant as to the different methods of reproduction employed should at any rate, after paying a little attention to the descriptions given, avoid making designs that are almost impossible to reproduce satisfactorily. The object of this chapter is not to teach the student how to reproduce his drawings by means of the processes described. The only reasons for dealing with the subject are to enable him to produce workable designs, and at the same time to give him an added interest in his work by an elementary knowledge of the methods of reproduction.