Caffenol: we developed four rolls in instant coffee, so you don’t have to (but you should)

It sounds like a prank: mix instant coffee, washing soda and vitamin C in tap water, pour it into your developing tank, and twelve minutes later you have negatives. But caffenol is real chemistry — the caffeic acid in cheap coffee is a developing agent, the soda provides the alkalinity, and the vitamin C supercharges it.

After the recipe came up (again) at a crit night, four of us each sacrificed a roll to settle it.

The house recipe (Caffenol C-M, per litre)

• 54g washing soda (sodium carbonate — the laundry aisle kind, not bicarb)
• 16g vitamin C powder
• 40g of the cheapest, nastiest instant coffee you can find (the posh stuff genuinely works worse)

Mix in that order, wait five minutes for the froth to settle, and use at 20°C. We gave HP5 twelve minutes with normal agitation; a fifth test roll got 70 minutes of stand development for comparison. Stop, fix and wash exactly as normal — your fixer neither knows nor cares what developed the film.

The results

Genuinely good. Full-bodied negatives, slightly more shadow speed than we expected, grain a touch softer than Rodinal, and a faint warm base stain that prints straight through. The stand-developed roll showed lovely edge effects around the drystone walls in Llanthony. Blind-tested against a D-76 roll at the following crit, nobody could reliably pick the coffee.

The catches

Your darkroom will smell like a greasy spoon for a day. The mixed developer is one-shot and keeps for hours, not weeks. And measure properly — this is the one hipster process where precision actually matters.

Total cost per roll: about 40p. Bring a roll to the next workshop and we'll develop it in the world's worst cafetière together.