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?
Four of us just did a proper side-by-side for the blog (write-up is on the news page now). Blind-tested against D-76 at crit, nobody could reliably pick the coffee. Use the nastiest instant you can find — the supermarket value stuff outperformed the good jar.