I've been experimenting with caffenol as a developer. Current mix: 54g sodium carbonate, 16g vitamin C, 40g instant coffee per litre. Stand development 70 mins at 20°C with Kodak TMax 400. Getting good results but tonality feels flatter than D-76. Anyone adjusted the recipe?
I use a slightly different ratio — 40g coffee and 8g vitamin C — and find it closer to Rodinal in character with a bit more speed. What film are you pairing it with?