Carbon Journal, Day 13
Day 13: "High Relief" Tissue
Turning a complete 180 from yesterday's journal, today we're going to be discussing a carbon glop recipe that yields high relief. In photography, relief is a characteristic unique to only a handful of processes, namely carbon transfer, photogravure, and woodburytypes. Here, the image is conveyed through a series of pits and valleys. Shadows are raised above the surface, while mid-tones are less raised, with highlights closest to the bare substrate. In many carbon transfer prints from the late 19th and early 20th century, relief is hardly noticeable, as carbon prints were typically double transfers; performing one transfer to an intermediate support, then transferring an additional time to a final support. In contemporary carbon printing, the vast amount of open information on the internet allows printers to refine their processes to exaggerate this unique characteristic.
Referring to previous carbon journals, we've already learned that image relief can be controlled by a number of variables. Amount of gelatin in glop, pigment loading, tissue thickness, and sensitizer concentration will all be important factors in getting dramatic image relief. Fortunately for this carbon printer, there are already hundreds of hours of testing and results in-hand, taking out a lot f the guess work that beginning prints can/will struggle with. Printing high relief, for me, will always have three constants: 10% gelatin concentration, pour thickness (120ml per 9x11" sheet), and pigment material (Graham's Lamp Black). These all boil down to personal preference, but eliminating unnecessary variables is key to repeatable success in carbon printing.
Pigment loading is one of two variables that I've been monkeying around with lately, and one that makes a world of difference in print relief. A standard pigment load of 1.5% (pigment to final glop concentration) will produce a nice, thin relief, with snappy contrast and smooth, silvery mid-tones. Decreasing this pigment load, as far down as 0.6%, will be the goal of this style of glop. Since the 1.5% and 1.0% concentrations have already been tested, my glop recipes will include a 0.6% and 0.8% pigment load.
The other variable that will determine value/tone in the high relief image is the sensitizer amount. Much easier to control on a per tissue basis than pigment loading (which needs to be made when mixing glop), sensitizer amount can be changed at will only an hour or two before exposure. My standard carbon negatives tend to need 10ml of 4% potassium dichromate and 10ml of acentone, applied over two successive coatings to achieve good contrast. When thicker, less pigmented tissue is introduced, I'm going to expect, from other carbon printers' observations, that a good starting point would be a lesser sensitizer strength, and more exposure. Assuming I can produce ~8 tissues over the next few days, my experimental high relief tissues will look something like this:
- 0.6% pigment + 3% sensitizer + 12 units exposure (twice reuglar)
- 0.6% pigment + 4% sensitizer + 12 units exposure
- 0.6% pigment + 5% sensitizer + 12 units exposure
- 0.6% pigment + 6% sensitizer + 12 units exposure
- 0.8% pigment + 3% sensitizer + 12 units exposure
- 0.8% pigment + 4% sensitizer + 12 units exposure
- 0.8% pigment + 5% sensitizer + 12 units exposure
- 0.8% pigment + 6% sensitizer + 12 units exposure
Tedious? Yes. Worth It? Stay tuned for upcoming results, and I'll let you decide. ;)