Bromoil once a mainstay of Pictorialism was for many years relegated to the dustbin of photography. With the renaissance of alternative processes, bromoil prints and transfers are being produced again. Both oil printing and bromoil are based on the same physical process. Gelatin that has been sensitized with a dichromate will harden when exposed to ultraviolet light. This process dates back to the origin of photography. While Fox-Talbot was experimenting in England with silver salts, in France Poitevin developed the process which lead to carbon printing, gum printing, oil printing and eventually bromoil. He found that a greasy ink was repelled from a gelatin that was swollen with water while hardened gelatin accepted the ink.
The basic process is to take a sheet of paper, coat it with several layers of gelatin and the sensitize the gelatin with a dichromate. This paper is now UV light sensitive. A negative is placed in contact with the sensitized paper and exposed to a UV light source. The light source can be as simple as the sun but exposure under UV lights or a plateburner will provide for more consistent exposures. No development is needed; the exposed paper is washed to remove the unexposed dichromate. The gelatin that was exposed through the thin areas of the negative (the shadows) is hardened and will not absorb much water. The areas of gelatin under the more dense parts of the negative (the highlights) have received less UV exposure and less of the gelatin is hardened. In these areas water is readily accepted by the gelatin. You can readily feel the difference between shadow and highlight by running a finger over the surface of the print. Lithography or etching ink made with an oil base can now be applied to the print. Rollers or brushes can be used to apply the ink. The ink adheres to the gelatin surface in proportion to the degree of hardening present. The choice of the paper plays a major part in the final image. The texture of the paper is readily noted in the oil print.
Oil printing is making a resurgence in part because of digital photography. Making an enlarged negative has always been one of the drawbacks to oil printing. Inkjet printers are now able to produce enlarged negatives and this allows artists to combine digital capture and image processing with a hand made printing process.
Oil printing was common in the late 19th and early 20th centuries but fell out of favor with the advent of commercially available silver gelatin paper. In 1907 Wall described the use of silver gelatin paper to create a print similar to the oil print. A silver gelatin print was made which was then processed in special bleach. This bleach removed the silver salts and replaced them with a dichromate. The dichromate hardened the gelatin in proportion to the amount of density that the silver had created. This process allowed the use of a small camera negative. No longer was the size of the oil print limited to the size of the negative. A photographic enlarger could be used to make the silver gelatin print which could be processed to make an oil print. This new process combined the then common silver bromide gelatin print with the oil printing technique and was called “Brom-oil”.
Initially most all silver gelatin papers could be used to make bromoil prints. The silver print is made; then the print is bleached and re-fixed with hypo. The swollen / hardened print (now called a matrix) is inked with a brush or roller with lithography ink. The gelatin of a bromoil matrix cannot swell as much as an oil print and an ink with less oil is used.
Bromoil depends on have silver gelatin paper. Until the 1950s the major photography companies made paper specifically for bromoil. This paper was not “supercoated”. Supercoating was done to most silver gelatin papers so that the emulsion was less prone to scratching while being processed. With the rise in “straight” photography, there was less and less demand for bromoil supplies. With fewer supplies available most photographers abandoned bromoil. In fact, even supercoated papers can be used to create bromoil and all my bromoils are made on supercoated paper. The problem now is will there be any silver gelatin paper available at all in light of the overwhelming dominance of digital photography.
The inked bromoil matrix is an end in itself to some workers. These prints are ink on a gelatin coated piece of paper. The ink however can be transferred to another piece of artist paper by using a press. The result is a photographic image made of ink on paper. In addition the transfer process allows the use of a wide variety of artist papers. Bromoil transfers require the gradual build up of density since the ink transfers more easily from the highlights than the shadows. Multiple inking and multiple runs through the press are required to complete a successful transfer. The bromoil transfer is the most archival types of photgraphic image since it is only ink on paper. The image is literally pressed into the paper. For me the bromoil transfer is the ultimate in printmaking.