An interesting recipe, yet to be tried now proven to work very effectively, although longevity – both as stock and in dish – is yet to be confirmed.
I’m home now, and the amidol developer is good as new! I think it’s safe to say it works well enough to be useful, even though I can’t say exactly how long it will last in concentrate. I know the working solution lasts several days, so that’s a victory in itself. My unorthodox method for preserving the amidol concentrate is to use a suspension of amidol in a solution of ascorbic acid and benzotriazole in glycol. I dissolve the ascorbic acid and bzt in the glycol, and then when the solution is still warm, but not hot, I add the amidol. Some of the amidol dissolves, but much remains in suspension. My thinking is that it doesn’t matter much whether the amidol is dissolved or suspended, so long as it’s protected from oxidation, which it is in the glycol solution. When the concentrated suspension is added to the 3% sodium sulfite B solution, everything dissolves almost instantly, and the pH is 7. The ascorbic acid preserves the working solution admirably. I’ve been using the same working solution for several days now, making a test print from the same negative to begin each session. Here’s the formula:
DeFehr Amidol Suspension Print Developer for Chloride Papers
Concentrated Suspension – Solution A
Propylene glycol 50ml
Ascorbic acid 10g
Glycol to 100ml
Dilute 1:50 with 3% sodium sulfite solution (Solution B) to make a working developer solution. The working solution keeps for several days if it’s stored in a closed bottle between sessions.
Gives neutral tones on Azo and Fomalux 111. Compatible with water bath technique for contrast control.
I think the suspension should last a very long time on the shelf, but since I’ve only just begun using my first batch, I can’t say for certain how long it will last. In any case, it’s very economical and convenient, and gives beautiful, solid blacks, and platinum-like highlights, with a long scale of greys in between.
I mixed this recently and would add the following observations:
- the TEA (triethylamine, triethanolamine) needs to be added to the initial 50ml of propylene glycol in order for all the constituents to dissolve effectively.
- a magnetic stirrer with heating plate is really needed in order to dissolve all the constituents; temperature should not be allowed to rise too high as the mixture fumes (some ammonia is given off). I heated it to about 40 deg. C.
- the final mix of Solution A is dark brown. All the amidol appeared to dissolve and the consistency of the final 100ml solution is syrupy, a bit like HC110 developer concentrate.
- a syringe is best to measure the small amounts of ‘A’ required; amidol stains everything it touches, so wash everything thoroughly immediately after use.
- a 3% solution of sodium sulfite is prepared by dissolving 30g in 1000ml of water.
- my final dish mix was 20ml of Solution A and 1000ml of Solution B. This was a faint yellowish colour in the dish.
- development times with Agfa MCC, Adox Nuance and Fomatone fibre papers was around 3-4 miutes at 20 deg.C. to obtain maximum black.