The personal control of the tone values of the print, which attains its maximum development in bromoil printing, is equally possible in bromoil transfer.
The picture is obtained on an uncoated paper and, therefore, the prints are of a character which hitherto could scarcely be obtained.
The finished prints, if the paper is properly chosen, can be retouched as much as desired.
From a single bromoil print a whole series of impressions can be obtained, which may either be all alike or quite different. They can be made heavy or light, in one or more colors, or even in polychrome, according to how the re-inking is done.
The transfer process is also very cheap, as the papers used are naturally much cheaper than photographic printing papers. Moreover, one can make the pulls from small bromoil prints on larger sheets, so that the picture may be suitably surrounded with white margins.
The following details should be observed in the preparation of bromoil transfers:
The bromoil print designed to be used as a print-plate can be made on papers of the characters described in Chapter I, [page 13]. The bromide paper need not necessarily be free from structure, for with the pressure to which the sheet is subjected in the transfer, the effect of the structure is lost. The structure of the bromide paper may also be reduced by passing the bleached print through the rollers of the transfer machine under heavy pressure before inking. The bromide print or enlargement must be kept very clean and free from fog, since the cleanness of the high lights plays a very important part in the transfer. The inking is done in the usual way; only one should use all possible means to obtain the greatest possible cleanness of the high lights, and good modulation. After inking-up, any brush hairs and especially any little particles of ink that are not broken up must be removed, as the latter are especially troublesome in the transfer.
The process succeeds best when the bromoil print has as high a relief as possible. Such a relief facilitates and requires the use of inks of soft consistency; soft inks adhere to the gelatine film far less firmly than harder ones and, therefore, transfer very much more easily to the transfer paper. A simple experiment makes this fact very clear: if the tip of the finger is placed on a part of the bromoil print worked-up with hard ink, some of the ink sticks to the finger, but at the most there is formed on the print an impression of the tip of the finger, as the place touched still retains the greater part of its ink. If, however, the tip of the finger is placed on a part of the print worked up with soft ink, the latter will be almost entirely removed. This may serve to show why bromoil prints which have been entirely or chiefly worked up with hard ink cannot be entirely transferred to the transfer paper. The shadows especially, when covered with hard ink, are likely to appear much reticulated in consequence of the imperfect transfer of the ink.
To obtain with certainty a faultless bromoil transfer, soft ink should therefore be used; the softening of the ink must naturally not exceed a certain limit, because otherwise the high lights will take the ink and a clean pull cannot be obtained. In order to be able to use a soft ink successfully, the relief of the bromoil print must as a rule be kept rather high; hence usually water baths of suitably high temperature should be used. It may, however, happen, especially with contrasty prints, that the gelatine in the high lights becomes too soft, and if it is not already damaged when taken from the warm water, it pulls off in inking-up or in the transfer. In order to avoid this, it is best to use the ammonia bath described on [page 45].