Yes, we all know that one weekend’s workshop for learning the basics of both bromoil and gumoil printing is far too short, but nevertheless, the students were enthusiastic and started some great gumoil work to be continued later on their own.
Gumoil printing is an alternative photographic printing process, developed by Karl P. Koenig in 1990’s. Although it is not as historical as many other alternative techniques, it is clearly related to both gum printing (which uses gum arabic as binder to pigment) and bromoil (which forms the image with oily printing inks).
Every gumoil print is a unique piece. The process begins with coating paper with liquid gum arabic which is sensitized to light, continues with exposing the paper to UV-light in contact with a positive film, and ends with inking with oil color pigments after developing the image in water. After the inking stage the excess color is wiped off, and if multicolor image is desired, the print is treated shortly in bleaching bath. This will remove some of the hardened gum arabic and allow adding the next color.
Sequential bleaches and inkings can then be done until the print is finished, the whole process may take take several days or weeks. Adding more colors will produce more tones and sense of depth.
Digital positive films for exposing gumoil can be printed quite easily with an inkjet printer – the UV-blocking color doesn’t need to be extremely accurate, and one can experiment with different output options.
Just before the end of the semester a group of students of Professional specialization (SAMK / Fine Art KankaanpĂ¤Ă¤) tried their hands at bromoil and gumoil printing in a weekend workshop. Here is a brief story of the bromoil part – we will report on our gumoil efforts in a few days.
In the classic bromoil technique, made up in early twentieth century, an ordinary b&w photograph’s silver image is bleached and replaced by lithographic printing ink. The bleaching solution will also harden, or “tan”, the gelatin of the photograph in proportion to the amount of silver. When soaked in water, gelatin will swell, forming a relief that will accept the oily printing ink in shadows and midtones, but will reject it in highlights. The original photographic image will reappear by inking the print with brushes and/or rollers.
Bromoil printing is very much handwork, and every print is unique. The final print appearance will depend on brushes or rollers that were used, intense and shades of the inks, the printmaker’s individual technique, etc. There are three basic stages in the process:
The Silver Print
Many “old-fashioned” fiber papers are said to work well in bromoil technique, but with our limited experience we had certain difficulties with others but Bergger Brom-240, which is manufactured particularly for bromoil printing.
You can print the silver print as usual with an enlarger, or using a digital negative as we did in this workshop. We processed the image files using the same methods as before for basic silver gelatin printing (see earlier post on colorized negatives), with the Photoshop correction curves and UV-blocking colors.
The common rule is to print this silver print in notably lower contrast than normally, so that there is good tone separation both in shadows and highlights – the contrast will be increased when inking the print later. Most common paper developers will do nicely (when diluted more than normally), but all fixers (especially those with hardeners) cannot be used.
As a rule, the print should be exposed more than when making normal prints, doubling the exposure is a good starting point. The dilution of the developer and the length of developing time will modify darkness and contrast. After developer, stop bath, fixer, and washing the print is dried and can be stored, or the next step (bleach) can take place right after the final wash.
If the print is dried after the previous prosessing, it is a common practice to “superdry” it before bleaching – it can be heat dried with a hairdryer for one minute. The print is then soaked in water for three minutes or so, and immersed in the bleach solution (in dimmed lighting) for about 8 minutes (or until the image has disappeared as completely as possible), with constant agitation.
After bleaching this matrix is washed for 5 minutes, fixed once again, washed and dried.
The dried matrix is soaked in water (at room temperature) for about 5 minutes. The excess water is then wiped off with paper towels. A small amount of lithographers ink is spread on a glass plate to form a thin layer. The ink is stippled with a brush and dabbed on the glass to make another patch of ink, which is then used to charge the brush for inking the print.
The print can be put on a clean plate of glass, and it is first inked all over with a brush. It will then look dark and muddy, but the tone range can be evened out and made more contrasty by rolling with a wet foam roller. Also this first inking can be done (more quickly) by spreading the ink onto the print with a rubber roller.
After the preliminary inking the print may need to be moistened again, and the excessive water wiped away. Inking is then continued until the print looks finished. The print should then be left to dry completely over a few days.