About 30 years ago, I experimented with carbon prints from enlarged positives. Last winter, I did a few more tests, with fair results. Then, I decided to focus on enlarged negatives, so put printing from positives on hold. So I'm sharing this to help others.
We all know regular carbon prints that use very dark pigments in dichromted gelatin on a tissue that are transferred to a piece of sized white paper. Since I do everything backwards , I tried printing using a white pigment in dichromated gelatin on a tissue transferred to a piece of black sized paper. It worked well after adjusting formulas and thicknesses a bit. Pretty straightforward. Since this was obvious, I assumed this had been done before.
I used zinc oxide powder, which is archival and inexpensive as well as having anti-fungal properties with gelatin. Cadmium oxide is preferred for oil paints since zinc oxide is incompatible with them, but it would likely also work but be more expensive. Need to use isopropanol to break surface tension when mixing with gelatin, just like carbon powders. I used a black gesso type of acrylic for the black sizing on the paper, which was a watercolor type.
There are several advantages to this style printing.
1. Light transmission through the tissue is much better, greatly reducing exposure times and making visual exposure determination via the printout image much easier. This also makes halation at the tissue a problem if a white plastic like Yupo is used. I used a clear polyester sheet for the tissue, and black construction paper for anti-halation. Black Yupo would be good if it exists.
Gelatin separates from mylar really easy.
2. Prints directly from an enlarged positive, much easier to make than a negative. I haven't nailed the optimal density range needed for the positive yet, but it is higher than standard carbon prints I believe. Contrast control is also different and works the same with changing dichromate concentration. Pigment concentration has less effect on contrast then with dark carbon printing. Plain old ortho litho film works fairly well under the enlarger and processed D23 at 1:7 for 2-4 minutes with constant agitation. X-ray film would likely be a better choice.
3. Better depth and presence is possible, I believe, although I have not perfected this yet. This favors thicker gelatin. Unlike all other prints, other than Ambrotypes, light illuminating the prints is single pass only. The background is black or dark, so light does reflect back through the emulsion as it does with all other processes to my knowledge. The whites are raised up physically with thicker gelatin on the print surface, with the blacks deeper behind, which is more natural.
I'm building cameras and taking pictures this summer, so may not get back to darkroom work until winter. I also need a densitometer to proceed.
Are there other printers out there that have experimented with this? I would think so, but haven't heard of any, but I've been out of the loop most of my life. Actually, I kinda like working alone.
Bookmarks