10 minutes at 20°C/68.0°F
Reinhold's recipe (caffenol.blogspot.com), slightly modified. Less soda, making it less active, but gives slightly finer grain. This is called the "reduced soda" version of Caffenol.
40g/l Instant coffee
40g/l Sodium carbonate
16g/l Ascorbic acid
1min inversions initially, 3 every minute thereafter. Stopped with water (2 times to remove the coffee), fix, wash as normal.