I'd like to introduce a new developer I've been testing for some time, and will continue to test and use. I call it Obsidian Aqua, for its scalpel-sharpness and water base.
Obsidian Aqua is very closely related to Hypercat II, but takes advantage of some of the opportunities an aqueous solution provides for economy, without sacrificing keeping prperties. The main reason for using propylene glycol in Hypercat II is to extend its keeping properties, but this comes at at some cost. PG is not locally available in many places, and is expensive to ship, and adds considerable expense to the developer. In Obsidian Aqua I've tried to maximize keeping properties while minimizing expense, including shipping costs, by utilizing locally available ingredients where possible, including the use of distilled water as the solvent. Like Hypercat II, OA uses catechol as its sole developing agent, but OA is preserved by metabisulfite in the stock solution, instead of ascorbic acid, and retains carbonate as the accelerator. OA can be made up in sodium or potassium metabisulfites and carbonates, depending on availability.
To maximize the keeping properties, the stock solution is highly concentrated. This allows for a higher ratio of catechol to metabisulfite, and a lower ratio of metabisulfite to water compared to other catechol staining developers, which simultaneously improves stain formation and keeping properties. A working solution of catechol/carbonate developer with appropriate carbonate content requires practically no preservative. The preservative is primarily required for the stock solution.
To make a working solution, the OA stock solution is dissolved into a solution of 6.66% carbonate, and how this is managed will depend on the carbonate used, and the preferences of the photographer. A 66.6% solution of potassium carbonate can be made by dissolving 666g of potassium carbonate to make 1 liter of stock solution, or 6.66g of either carbonate can be dissolved in a liter of water to make a working solution, or any number of other possibilities. The important thing is that the working developer contains 6.66g of carbonate/ liter.
Obsidian Aqua
Distilled water 700ml
Metabisulfite (sodium or potassium) 20g
Catechol 250g
Distilled water to 1 liter
Dilute 1:500 with 6.66% carbonate solution (sodium or potassium, depending on which metabisulfite is used in the OA stock solution). 1 liter of Obsidian Aqua makes 500 liters of working solution.
Develop TMY-2 12:00 @ 70F with *geometric agitation sequence.
Obsidian Aqua produces negatives of unsurpassed sharpness, excellent gradation, very fine grain, and full film speed. OA can be used with rotary processing, but with some loss of film speed. I hope this developer will be more convenient for my friends overseas, who often need to order supplies from outside their own countries. I highly recommend
Artcraft Chemicals for catechol. Artcraft offers 250g of catechol, which wouldn't require any weighing of the chemical to make up the stock solution; just mix the entire amount to make 1 liter. The metabisulfite is not critical, and could be measured with measuring spoons if no scale is available. 1 level teaspoon of metabisulfite weighs approximately 6.5g, so 3 tsp/ liter is close enough.
Obsidian Aqua stock solution should keep very well. Though I have no stock solution older than 6 months, I expect it to last at least a year in a partially full glass bottle. Time will tell.
I hope this formula is useful for anyone desiring the sharpest possible negatives with the best overall Image Quality, at the least possible expense, wherever one might live.
* The notion of a geometric agitation sequence was recently suggested to me, and I've been using it with good results. My method is as follows:
I use a count up timer, and begin by agitation continuously for 1 minute. Then I reset the timer and agitate for 10 seconds, according to the following progression (in minutes): 2, 4, 8, 16, 32, etc.
A geometric agitation sequence seems appropriate for this kind of very dilute developer, and my results bear this out.
Originally Posted by Jay DeFehr
I'd like to introduce a new developer I've been testing for some time, and will continue to test and use. I call it Obsidian Aqua, for its scalpel-sharpness and water base.
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