Bromoil printing and bromoil transfer

by Emil Mayer

Bromoil prints which are to be used for transfer must, as already mentioned, always be kept very clean. This is necessary for the following reasons. In the transfer the ink on the high lights transfers completely in every case to the transfer paper, for the high lights are in the highest relief, and the ink adheres to them very lightly. On the other hand the ink is generally not completely removed from the shadows, as they have the lowest relief and, in consequence of their tanning, the ink adheres to them more tenaciously. Thus it happens that the transfer is usually somewhat shorter in gradation than the original bromoil. Allowance must be made for this, and the bromoil print should be made considerably more brilliant than the transfer ought to be, unless low-toned transfers are intentionally sought.

In order to obtain clean, sharp edges the bromide print when dry should be cut to the desired size and a small tab of paper left at one corner, which is useful for hanging it up in the further processes, whereby any damage to the film of the picture itself is avoided. This little tab should be cut off just before inking. If a plate mark is desired, the print should be made with a suitable narrow white margin.

The finished bromoil print can be immediately used for the transfer. If it is not used at once, it remains fit for transfer until the ink begins to harden.

Any desired kind of paper may theoretically be used for the transfer; but obviously, the success of the transfer greatly depends on the choice of the paper. The finest effects are obtained on matt and absorbent, but strong and well-made papers, the very best being papers intended for copper-plate printing. As the ink penetrates into the fiber of such papers to a certain extent, they give beautiful transfers with an absolutely matt surface. Absorbent papers also make it possible to transfer almost all of the ink from the bromoil. It is different with sized or highly calendered papers. With these, the ink only penetrates a very little way because of the film of size. The ink, therefore, lies chiefly on the surface of the transfer and appears glossy in the shadows; also, as it is not sufficiently absorbed by the transfer paper, the transfer of the ink from the bromoil to the paper is usually not complete.

It is advisable, when using calendered paper, to remove the gloss by preliminary dipping in water. Other kinds of paper also frequently give better transfers, if they are first moistened; this is most easily done by dipping them in water and then drying them between two blotters.

Papers which are inclined to blister because of short fibers easily split in transfer, as parts of the surface of the paper adhere to the high lights of the print and tear away.

Such papers may be made available for transfer, if they are coated with two per cent wheat starch paste and allowed to dry (Process of E. Guttmann). This is prepared by stirring up 2 g (60 gr.) of wheat starch in a little cold water, and adding to the mixture 100 ccm (3½ oz.) of actually boiling water, stirring well and allowing to cool.

The blistering of weak papers must be differentiated from the sticking to the transfer paper of parts which are too much swollen; in this case the surface of the paper remains undamaged, but the gelatine film of the high lights is torn off and adheres to the transfer paper. As a rule, this only occurs with those parts that are swollen too much, when too great pressure is used in the transfer. The preliminary sizing of the transfer paper with wheat starch prevents this also. Parts of the gelatine film which have high relief may also be protected from sticking to the transfer paper by a slight coat of varnish.

The best machine to use is that described by E. Guttmann on [page 153]. It has proved satisfactory in every way, especially as it permits accurate and easy regulation of the pressure of the rolls. If such a press is not available, an ordinary burnisher can be used. The simultaneous movement of the rolls in burnishers is produced as a rule by two gear wheels. The inaccurate fitting of the gear teeth, however, causes periodic irregularities in the pressure, which cause trouble in the transfer. In order to prevent this one of the gear wheels should be removed, so that the simultaneous movement of the rolls is produced by the pressure alone. A burnisher is useful for the preparation of transfers only if it is possible to obtain sufficient pressure on the rolls. On the other hand it is difficult to obtain with this machine the necessary regulation of the pressure during the transfer, which is described in the following paragraph.