Bromoil Process Guide, Meaning , Facts, Information and Description
The Bromoil Process is an early photographic process. It was very popular with the Picturalists during the first half of the twentieth century. The soft, paint-like qualities of the prints are very typical for this genre.It was based on the oilprint, which had the drawback of being a contact-print process. This made it necessary to use negatives with the same dimensions of the positives.
In 1909, E.J. Wall described theoretically how it should be possible to use a smaller negative in an enlarger to produce a silverbromide positive, which should then be bleached and hardened, to be inked afterwards like the oilprocess. Welborne Piper later executed this theory in practice, and so the bromoil process was born.
To explain the bromoil process, it is helpful to look at the oilprint first:
The prints are made on paper with a thick gelatin-layer that has been sensitized with dichromate salts. Exposure using a negative for contact-print leads to hardening of the dichromated gelatin, in direct relation of the amount of light received. After exposure, the print gets soaked in water. The non-hardened parts absorb relatively more water than the hardened parts, so after sponge-drying the print, while still moist, one can apply an ink on oil-base. Lithographic ink is used. The non-mixing character of oil and water results in a colouring of the exposed parts of the print, creating a positive image.
Bromoil prints are a direct variety of this process: One starts with a normally developed print on a silverbromide paper which is then chemically bleached and hardened. The gelatin which originallly had the darkest tones, is hardened the most, the highlights remain absorbant to water.
This print can then be inked like the oilprint.
Long-term effects on stability:
A non-adequate rinsing of the chromesalts can lead to discolourations of the prints under influence of light in the longer term. The irregular thickness of the gelatin-layer can, in unfavourable conditions, lead to stresses in the pictorial layer, which can be damaged this way.
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