Bromoil printing and bromoil transfer

by Emil Mayer

The marking of the individual layers may be done very simply and accurately if it is carried out as shown in the accompanying diagram. This marking of the layers has also the advantage that we may use it for all sizes with slight alterations for individual cases. The lay-out is very easy. The pasteboard which carries the plate-mark pattern is cut accurately right-angled and must be about 2 cm (¾ in.) larger all around than the transfer paper that is to be used. On this board we now draw, exactly 2 cm below the upper edge, a sharp line with ink that will not smear, such as waterproof drawing ink, stopping exactly also 2 cm from each edge. Then this line is bisected and the center point marked zero; right and left of this zero point we now draw equally distant upright lines, about ½ cm (³⁄₁₆ in.) apart, which are numbered 1, 2, 3, ... to the ends of the line. Like divisions are drawn on the plate-mark pattern, or if this is not to be used, at the place it should occupy. The bromoil and the transfer paper are now laid down with the help of these lines so that the upper corners are equidistant from the zero point, which can be very easily done. These location guides are also very convenient in combination printing.

We now have lying in front of us one on top of each other: two pressboards, an ordinary pasteboard, the copper-plate blanket and the pasteboard with the plate-mark pattern and the marks for locating the paper.

Now the bromoil print is lifted from its pad by passing a knife under its edges, and laid carefully with its back on the worker’s left hand. Thus the print can be laid down face up without danger of damage on the plate-mark pattern, adjusting it by the position guide before sliding out the hand, all without touching the face of the print. Great care must be taken that the print lies absolutely flat. It will adhere to the pasteboard without any aid except its own moisture. Now we take the printing paper, hold it at the upper third of its surface with the two hands and bring the upper edge to coincide with the pencil lines on the pasteboard which carries the plate-mark pattern, taking care that it does not touch this pasteboard. When the edge of the paper and the pencil lines coincide, the paper is carefully allowed to drop into position from the top to the bottom. It now lies on the bromoil print; now, holding it very gently on the bromoil print with one hand, the previously prepared copper-plate blanket is spread out with the other hand over the paper and pasteboard, and the two pressboards are placed on the cloth in the same way. Care should be taken that the whole arrangement is fairly evenly made up, so that none of the edges of the boards or blankets project beyond others. If this precaution be omitted it may happen that the transfer paper is squeezed into wrinkles running from the edges to the middle, which may even encroach on the print itself. These squeezed-in wrinkles, which, if the pressure be great, may appear like sharp cracks, make the print useless. This whole manipulation is rather difficult to perform at first, but it is learnt very rapidly, especially if the first experiments are made with a damp sheet of paper the size of the bromoil print instead of the print itself, and one thus becomes expert.

When the press-pack has been made up in the above-described manner, it should be taken firmly in both hands, so that nothing can shift, and the upper edge placed on the machine table and guided between the rollers, the separation of which must be such that they just grip the pack without exerting any pressure. This separation must be determined by experiment. The pack should then be gently drawn through until about 4 cm (1½ in.) of its lower edge remains protruding. Shifting is then no longer possible. The rolls should now be tightened, for which purpose the central spindle should be given six to eight half revolutions. The exact pressure cannot be prescribed, but it will always be better to begin with light pressure. The handle is again turned and the pack drawn through the press, until its upper edge sticks out about 4 cm (1½ in.). This process is repeated four times—twice in each direction. If, after the fourth revolution, we carefully lift up the upper layers including the paper—obviously while the lower edge is still held fast for about 4 cm by the rolls—we can inspect the first impression and will see that the high lights and fine half-tones have already given up all their ink, while the deeper tones still look very flat. The paper should be allowed to drop back again gently, and then the other layers. Then the pressure is increased by giving the central spindle about three or four half-turns, as, after the first impression, there is little danger to either bromoil or transfer through heavier pressure, and the pack is again passed through the rolls, but only twice, once in each direction. If the print is now examined again it will be found that the full half-tones and the lighter shadows are already transferred, but that the deep shadows do not appear in full tones. Then the printing is repeated with still greater roll pressure, three or four more half-turns of the central spindle; again the pack should only go twice through the rolls. Another examination should now show the print in full vigor in all its details. If, however, it should happen, especially when using rough papers, that the shadows do not yet appear quite deep enough, one should print again twice with increased pressure. All the ink which was on the bromoil print will now be transferred to the paper; if the printing was carried out properly the bromoil will look as if it had not been pigmented at all.

It should never be forgotten that the rolls ought never to be so strongly screwed down that they can only be started by great effort; they must always move easily, and with little muscular effort. Repeated slow passage of the press-pack through moderately tightened rollers is always more advantageous than a single printing under very heavy pressure.

Heavy pressure not only endangers the bromoil, since the gelatine film, especially in the lights, adheres to the paper and tears when removed, but the transfer also, because the water, pressed out quickly and with great force, is deposited in the ink in the form of fine globules. After evaporation, which takes place very quickly, these places show curious, light, circular or elliptical spots, which produce the general impression of a picture painted in the pointillist manner—an undesired effect which, however, may occasionally be satisfactory.

It is very advisable to turn back the central spindle before finally taking the press-pack out of the machine, as otherwise one may uselessly and prematurely ruin the components of the press-pack.

The bromoil can be immediately immersed in water and again pigmented—as was done at first, or with different ink. This process may be repeated until the paper breaks down, with careful treatment in printing and suitable stout bromide paper, up to twenty times.

If the pressure of the rolls was too great, then the film shows blisters, which at first, and if they only appear here and there, are harmless, even when they occur on important parts of the print. If their number increases, however, it is better to make a new bromoil.