Everybody that tried this recipe comes to the conclusion that OK, it works, the film is developed in 30 minutes but it is a dirty developer, the film remains foggy and stained and with hudge grain. For playing with it is OK but to have decent developed films, better another choice. There have been several contributes to turn Caffenol a decent developer, mainly from Reinhold who proposed several recipes of Caffenol combined with Vitamine C or, better said, with sodium ascorbate.
Caffenol film developer
Water 8 fl oz Arm & Hammer Washing Soda 2 tsp Folger's Coffee Crystals (not decaf) 4 tsp
Mixing Instructions: Mix soda until completely dissolved and solution is clear. Add coffee, mix until all grittiness is gone and solution is uniform. Let stand 5-10 minutes until microbubbles clear. Use within 30 minutes. Dilution: Use undiluted. Usage: 30 mins. Notes: Gives imagewise stain and general (fog) stain. All teaspoon measures should be level, or slightly rounded for coffee crystals.
Recently, at Flickr, somebody started complaining about caffenol and he (or she) was going to give up using Caffenol for the reasons I said before: stain, fog, grain.
I started then to test several possibilities, under my opinion that a developer must be as simple as possible and with the minimum amount of chemicals. Using stripes of film, I made a solution of coffee and start increasing the amount of alkali, at that time I used Sodium Hydroxide, until I was sure that some development would happen. I exposed then cheap films like Polypan F and Shangai GP3 and the results were more than satisfying. I can say now that coffee is an excellent developer, at least for the films used.
The recipe of Digital Truth given above is a bad recipe. On the other hand the quantities measured in spoons may work differently for different people.
The recipe I use now is like this and I am calling it Caffenol Black or Caffenol Solo:
500 ml of water
20 g of soluble coffee
5 g of Sodium Carbonate*
Water to make 1 liter
First dissolve the coffee in water and then add the alkali. The order is coffee-alkali and not like the recipe of Digital Truth says. It works much better. Sodium Carbonate can be added as solution, if you dissolve 100g in 1000 ml, use 50ml of this solution that may be kept for other Caffenol batches.
The Caffenol should be used just after preparation and it takes some 60 minutes (and not 30 minutes) to develop your film without stain, without fog and with very acceptable grain.
* Important notice: after discusssing this with Reinhold, who had bad results with the recipe above (underdevelopment, no shadow details), the 5g/l are not a must, Important is to achieve the right pH that is about 10,4 to 10,6, according to my cheap pH-meter. Different coffees have different acidic properties and may need more or less alkali. I even have used Sodium Hydroxid, adding it drop by drop until I reach pH 10,4 and it worked.