Some ingredients and equipment for the Caffenol-C coffee developer.
The formulas I found on the net for Caffenol-C were a bit difficult to reproduce accurately. (There are too many measurements by level or rounded or heaped teaspoon or cup or ounce.) So based on one such formula I devised this as a starting point for my experiments.
Water(1) 300 ml
Washing soda(2) 12g
Ascorbic acid(3) 1.1g
Coffee granules(4) 8.5g
Of course, as you can see, I am able to weigh these ingredients to 0.1g. I guess you may have to use some other system if you don't have scales like mine!
- Dissolve soda in water. Leave to clear(5).
- Add coffee and ascorbic acid, dissolve and stand for 10 minutes. Use undiluted as soon as possible, but at least within 30 minutes.
For Agfa APX400 @400ASA, which normally requires longer development times than most similar films, I chose 15min development time at 20C.(6)
Wash rapidly in 4 changes of water at 20C (total time just less than 1 minute) before using stop bath and fixer.(7) These 4 changes of water seem necessary to remove the coffee stain and allow you to save the fixer and other chemicals for future re-use.
Then fix as usual.
(1) I used water at 20 degrees C. Warmer water may have been a good idea to help things dissolve. Eg use 2/3 of the water here at 30-40 degrees and then top up with cold water to 320ml or thereabouts (the final volume I ended up with).
(2) Washing soda used was "Dri-pak (dp) soda crystals", www.soda-crystals.co.uk, bought at hardware store. Main ingredient Na2CO3.10H20. Label says it is guaranteed >30%. (I presume that calculation reflects the water of crystalisation, but I wonder if there may be some residual NaCl in there too.)
(3) Linus vitamin C power, ordered from local chemist.
(4) "Nescafe original", freshly opened. Chosen not so much because it is my favourite (it isn't) but because it is ubiquitous and easy to obtain, and therefore (hopefully) with reproducable results. Most others should do just as well.
(5) It never really cleared at any stage. I made sure I let it stand for 10 mins and then used the stuff anyway.
(6) I sort of swished the chemicals round slightly once a minute by tilting the tank, rather than my usual inversion or stirring or rotating vigorously. (I have read that too much agitation is a bad thing, though don't know why.) This wasn't a well-controlled experiment, and I am not sure the negatives were exposed correctly (they could even have been as much as a stop out either way), but the end result was as good as I might hope on the first attempt.
(7) Next time I plan to wash 4 times in citric acid instead, and discard this citric acid afterwards. Citric acid crystals are easily available at nearby Asian grocery shops and are cheap - much cheaper than Ilford stop bath!