Caffenol-C derivatives all require three main ingredients. Vitamin C in addition to the basic original Caffenol ingredients of instant coffee and a pH regulating substance, normally sodium carbonate. The addition of vitamin C makes for faster development times, and it also goes a long way in hindering the coffee staining the negatives. It might introduce haze on some films, but that can be counteracted by using very small amounts of citric acid or potassium bromide. I chose to start with Caffenol-C-H for my TMAX100 and 400 films.
For every litre of ready developer you need the following ingredients:
- 54g of Sodium Carbonate (Washing soda, anhydrous)
- 16g of Ascorbic acid (vitamin C)
- 40g of Instant coffee (the darker and less palatable the better, preferably Robusto coffee as it contains more of the active agent caffeine acid)
- 1-2g of Potassium Bromide*
*TMAX films evidently are not susceptible to haze, so I cut back on the bromide to under 1g/l
Development times vary, depending on the film type and speed, and of course on your own preferences. 15 minutes at 20C/68F is recommended as a starting point. I´d seen examples of decidedly shorter development times that turned out quite nicely, so I thought I´d start off with 11-12 minutes. Thinner negatives would still be scannable, or so I thought.
My first film of TMAX100 I exposed a few scenes bracketed one stop above and below the nominal EI of 100. I dissolved each ingredient separately and bottled them for later use. I took into account the final mixing ratios so I could mix the three main ingredients in equal amounts totaling 490ml, topping off with 10ml of 1g/10ml concentration Potassium Bromide solution. (Hopefully the pre-mixed ingredients will not go bad before I have time to make use of them)
Film loaded in a Paterson 4 tank, 11 minutes development, normal agitation scheme (1min initially, 10s every minute thereafter), water stop bath (1min), TMAX fixer (5min), washing and photo-flow (20min).
How did they turn out? Well, I should have listened to Reinhold. The negatives where thin, a bit too thin. However there were quite a few negatives which were no more difficult to scan and post-process than TMAX developed negatives, just different.
Here are a few examples (test images, not chosen for their photographical merit, click to enlarge):
|EI 100, levels adjusted, exposure ramped up 0.7,|
|EI 100, levels adjusted, exposure ramped up 0.7, |
|EI 100, levels adjusted, no other post-processing|
With a little bit of help from my Scandinavian Apug friends I decided to up the development of the next film by 2/3s of a stop. More on the results from that film later.
Not counting the obvious underdevelopment, a fault of my own doing, I think the negatives came out pretty well. As promised, Caffenol does well in drawing out shadow detail, yet retaining the highlight information. The contrast is somewhat subdued, probably not helped by using venerable single coated optics, and can be seen as a disadvantage in the darkroom, but an advantage in my book as it gives my scanner a better time of scanning the negatives.