LINE PROCESS.

The methods of drawing for reproduction by, and in compliance with the requirements of, a line process, are numerous and varied. They include pen, pencil, and crayon, and modifications and combinations of all three.

The information which I shall give is intended chiefly for such as know little or nothing of the manner in which such illustrations should be produced. Having already mastered the primary methods, the more practised draughtsman, knowing what any special reproduction process requires, will, to some extent, invent his own methods and often resort to some "dodge" which may occur to him, thereby producing some delightful and original result.

In describing the half-tone process we found the necessity of having an image in relief of such a character that we could print from it in ink, hence the intervention of a ruled screen, which broke up the flat even tints of the original picture into minute dots. Line processes, as the term implies, are used to reproduce an illustration which, as in a pen and ink sketch, possesses no flat tints, and requires no screen, the actual lines being reproduced in relief and printed in facsimile.

It will, of course, be remembered that a mechanical process block can only produce in simple black and white: that is, it either reproduces a line, to print black, or omits it altogether; so that a line drawn in grey ink, and another in black, would each reproduce exactly the same, namely black. Whereas in wash drawing we were limited to a few varying tones, we are now restricted to two—white and black—and, as may be seen by looking at any good line drawing, various degrees of shade are produced by a multiplicity of lines in greater or less proximity and of varying thickness.

Before proceeding further, I will give an outline of the three principal processes used for producing drawing in line. These are the swelled gelatine, the albumen, and the bitumen processes;—other processes exist but are little practised, and offer no advantages over the above. The albumen and bitumen methods are processes of etching on zinc and familiarly known as "zinco" line process; not so the swelled gelatine, as will be seen from the following description of it. Gelatine of a hard variety is melted in water with the addition of a small quantity of sugar and chrome-alum, and is then spread evenly upon a perfectly clean glass plate. This gelatine film is, when required for use, sensitised by immersion in a solution of bichromate of potassium, methylated spirits, and water. The effect of this is to render the film, to some extent, insoluble where acted upon by light; or, more correctly speaking, non-absorbent when affected by light. A negative, made from the original to be reproduced, is placed in contact with the sensitised film and exposed to light. The film, which it will be remembered is resting upon a glass plate, is then placed in cold water, with the result that those parts which have been protected from light absorb water and swell up, leaving the non-absorbent parts, which represent the image, sunk in. When this operation has been carried far enough, a plaster of Paris cast is taken, and from this a wax mould is made, which is practically a duplicate of the gelatine mould from which the plaster cast was made. Into the wax mould copper is deposited, precisely as in ordinary electrotyping, thus giving us a copper relief from a gelatine or wax mould made direct from the original.[2] This process, while a favourite with the artist, is not so readily used by the process worker because it is somewhat expensive, the average cost of a block being from 9d. to 1s. 6d. per inch. But the results are very fine, especially when a drawing has been made in ignorance or regardless of the requirements of process reproduction.

The zinc etching processes, by which the great mass of newspaper blocks are made, are less regardful of delicacies of execution which the swelled gelatine often reproduces with astonishing fidelity.[3]

In the albumen process the sensitive film is composed of egg albumen, bichromate of ammonium or potassium, and water, which is spread upon a zinc plate. After exposure to light under the negative, the whole surface is inked over with transfer ink, and then immersed in cold water and gently rubbed. The ink will wash away from those portions which have been protected from light by the opaque portions of the negative, and will adhere to those affected by light. Thus on a bed of zinc we have an ink image on a substratum of albumen, the exact copy of the original. The zinc has now to be etched with acid.

With bitumen the procedure is somewhat similar. The bitumen is first treated with ether, which will dissolve out only those constituents which, not being sensitive to light, are not required. The residue is dissolved in benzole and spread upon a zinc plate, as with the albumen process. After exposure to light under the negative, the bitumen film is washed with turpentine, which takes away all except those portions acted upon by light. The film is next washed in water and placed in a very weak solution of nitric acid, which at once attacks those portions of the zinc unprotected by bitumen. If what now remains of the film be inked over we shall have, as in the last process, an ink image of the drawing on a zinc base, and the plate is now ready for etching.

The etching is performed by successive baths of diluted nitric acid, gum and powdered resin being applied to the plate after each etching, and heated so as to run down the sides of the ridges of metal (which at each successive etching bath are gradually growing deeper) until the "biting" or etching be considered deep enough. The ink and substratum of albumen or bitumen are then cleaned off with American potash, and the plate is finally washed. Rebiting, or still further etching, may be required before the zinc relief is ready to be mounted on a wood block "type high" for printing purposes.

As in the half-tone process, I do not pretend to have given working instructions, but only such general particulars as may interest the artist or draughtsman whose work is to be reproduced. For either of these processes the average cost is 4d. to 6d. per square inch, with a minimum charge of 5s. for a single block. Each process has its special uses and applications; the process craftsman (whom nothing delights so much as a sharp, brilliant line) will usually recommend the bitumen, but the albumen method will often give a more pleasing result. As a general rule, if your work is placed in good hands, the particular process to be used is best left to them to decide, and if a proof be submitted some little alterations may be suggested which can be carried out by an engraver.

In the subsequent pages of this book I shall make little reference to these processes; enough has been said, and they are no part of the draughtsman's business, only it will be well to keep in mind throughout such general particulars as have just been given.

Little has been said with reference to the negatives used in reproduction; but as the draughtsman who also possesses some knowledge of photography may be tempted to copy his work himself, it may be well to point out that the negative image must be as sharp as it is possible to get it. The most trifling deviation in focussing, unnoticeable in ordinary photography, will tell seriously in making a reproduction; moreover the kind of negative one may have learned to make for ordinary photographic purposes will not do here. The function of the negative is, it will be remembered, to protect certain portions of the film from light, and to freely admit light where the image is, hence the denser portions of the negative must be very nearly, if not absolutely, opaque, and the image as nearly transparent as possible; thus giving what photography proper has taught us to abhor—a black and white print. With ordinary plates, the required amount of density is not always easy to get, and special photo-mechanical plates are supplied by Mr. John Carbutt, of Wayne Junction, Philadelphia, Pa., which give the desired result. These plates are slow, thickly coated, and capable of giving great density, all of which are characteristics peculiarly suitable to the purpose. But in the end the process man will not thank you for saving him the trouble of making a negative; he is accustomed to make negatives of a certain kind, and very properly prefers to do this himself.

Not the least contributory towards a good reproduction is the power which reduction from the original places in our hands. When making the copy negative it is most usual to make it much smaller, or, inversely, the original drawing is made a good deal larger than it is required to appear (See Illustration on page 72). A somewhat ragged line of (say) one-eighth of an inch in width, would, if sufficiently reduced in size, come out as a fine line no thicker than a hair. Though reduction carried to such a degree would be impracticable, a drawing twelve inches by nine inches, reduced to eight by six, will usually be advantageous. Not only is a certain degree of coarseness and roughness thus removed, but the lines themselves become smoother and rounder; lines, however, which are very close together, are apt to close up into a solid mass, both from the reduction and because lines sometimes have a tendency to thicken in reproduction—a point to be guarded against when drawing.

If a drawing be examined through a simple double concave lens, that is to say the reverse of a magnifying-glass, the effect of reproduction can be seen, and the result anticipated; such lenses, called "diminishing glasses," are sold expressly for the purpose.

The reader need hardly be reminded that everything on the drawing will be reproduced, except perhaps blue pencil lines, this colour being photographically white; hence all finger-marks, spots, and stains must be carefully avoided. No doubt these, and sundry faults in drawing, can be cut away by the engraver, but an ideal block is one which requires no such helps to perfection, but which comes from the etcher's hands ready for use, and to such an ideal even the tyro must work.

The strong point and chief recommendation of a process block is that it reproduces in facsimile the draughtsman's original; once introduce hand-work and it begins to lose this character; moreover expense and delay in production are incurred, again depriving the mechanical block of its distinctive and valuable features.

Sundry elemental methods of getting an image on to zinc for etching without the intervention of photography may perhaps suggest themselves to the reader. Thus, for instance, an outline drawing may be made in transfer ink on transfer paper and at once laid down on the zinc and etched. A glass plate, coated with a soft opaque substance, may have a design scratched thereon and be used in place of a negative; but such methods are crude and limited, and need not be considered here.

We will now pass to an examination of the various kinds of drawings suitable for reproduction by relief process blocks, describing as nearly as possible how they are made and with what materials.