The Essentials of Illustration / A Practical Guide to the Reproduction of Drawings & Photographs for the Use of Scientists & Others

by Thomas George Hill

Before sending any line drawings to press they should be carefully examined; pencil marks may be rubbed out, lines touched up, unnecessary lines removed by painting them out with white or black ink according to the background, and, finally, a frame ruled around, if necessary.

The amount of reduction, which should be marked clearly on the margin, requires very careful consideration since under reduction may cause the reproduction to appear too coarse whilst over-reduction may result in the loss of the finer detail and the drawing may, moreover, appear spiritless.

It must also be remembered that a reduction of, say, ½ linear means that the reproduction will be a quarter the area of the original.

The best way to indicate the reduction required is to draw a vertical or horizontal line, parallel to a side or the base of the picture, of the exact length; or, the line may be roughly drawn and its length indicated by figures thus ——————2½"—————.

The question arises as to when line drawings for reproduction by the zinc block should be employed.

The answer is, Whenever possible.

The advantages to a reader of having the illustrations in the text has already been commented upon. It is about the only method commonly employed in which practically everything depends on the draughtsman; the author thus exercises the greatest control. Finally the fact that it is very inexpensive will appeal to editors and publishers.

As a matter of curiosity, the present writer picked out at random a recent volume of a scientific journal to examine the illustrations; although there were a number of text figures, an examination of the plates—chiefly lithographs and collotypes—showed that there were a large number of figures which ought to have been in the text. A more detailed inspection of the plates was therefore made, with the result that nearly 200 figures were found which with the minimum amount of alteration—merely drawing in ink instead of pencil in the majority of cases, and leaving out unnecessary shading in the others—could have been reproduced by line blocks. If this had been done, a saving of over 20 per cent. could have been effected on the plates. Some of this would, of course, have been absorbed in the making of zincos, but not much, since line blocks of excellent quality can be obtained for 2½d. and 3d. per square inch. The above relates only to the most obvious examples; the saving in plates would have been enormous if the authors had drawn for the line process.

THE SWELLED GELATINE PROCESS. From the foregoing account of the line-block it may, perhaps, be thought that a drawing shewing the finest detail cannot be reproduced in the text by a relief block made by photo-chemical means. This is not the case; the swelled gelatine process is such that at its best the very finest work can be so reproduced. The method is not extensively used, chiefly owing to the remarkable amount of skill required to produce the best results and to the facts that the blocks take longer to make and are more expensive than the ordinary line block. This, however, should not militate against its use, for the increased cost is but very little, and the longer time in making, say two days, should not be of any consequence in a monthly or quarterly periodical. The great point in its favour is its great fidelity as compared with the ordinary photo-chemical relief blocks: for instance, a close cross-hatching reproduced by a line block will often come out as a series of white dots owing to the fact that at the points of intersection the black lines tend to thicken; hence, on printing, the white spaces, instead of being sharply cut and diamond-shaped, are rounded. This will not occur in a good block made by the swelled gelatine method. Further, the process does not restrict the draughtsman to dead black ink; the drawings may be made in pencil, crayon, or in ordinary writing ink: it is even claimed that wash drawings and photographs can be reproduced satisfactorily by this method. In the case of pencil drawings, the best results will be given when the surface of the paper used by the draughtsman is slightly rough; a pencil drawing on Bristol board, for example, will not be so well reproduced as one on ordinary smooth drawing paper. In brief, the process is as follows: a photographic negative of the drawing is made, and under it is exposed a bichromate gelatine plate. This plate is then developed in water. As already described, the gelatine will swell up in proportion to the amount of light to which it was exposed. The "positive" thus obtained will be in relief, the high lights being at a higher level than the shadows. A wax mould of the gelatine positive is then taken, covered with a thin layer of plumbago and electrically covered with copper. The "casting" so obtained is built up with metal and then mounted on wood in the same way as a zinco or a half-tone. The capabilities of the process may be judged by a study of Fig. 38, which is an extremely faithful reproduction of a lithograph, by S. Prout, by the swelled gelatine process.