Caffenol is the general term for film developers based on coffee. It is an acid wihin the caffine that actually processes the film. To make it work washing soda is added and to enhance the result iodized salt and asorbic acid, vitamin C.
The most ommon formula is generally known as Caffenol-C although actual quantities can vary between sources. I used a variant from a book 'Experimental Photography - a handbook of techniques' published by Thames and Hudson ISBN 8-0-500-54437-2.
The formula is:
54g Washing Soda (Sodium Carbonate Decahydrate)
16g Ascorbic acid (Vitamin C) - crystals are stated but I crushed some more readily aailable tablets.
This is dissolved in 300ml of water.
40g instant granular coffee (super market own brand)
Iodized salt (or 1g of potassium bromide)
This is dissolved in 700ml of water.
They should be mixed to make the developer when needed.
The above makes 1000ml. My tank took 300ml so I mixed 90ml and 210ml to make a working solution.
Processing is around 15 minutes at around 20 celcius. Precision does not seem to be important. I inveed a few times around once a minute.
Normal fixer is used. After developing the film should be rinsed with water to get rid of most of the developer residue. This usually means a few pours of water into the tank rather than the traditional single stop bath.
The slide show shows the processing materials and example pictures using Kentmere100 film taken on a Fuji DL-500 camera.