I wanted to post the Caffenol recipe I used before I started adding ascorbate. Here it is:
8 oz. Water
2 tsp (level) Arm & Hammer Washing Soda
4 tsp (slightly rounded) Folger's Coffee Crystals
Mix soda until completely dissolved and solution is clear. Add coffee, mix until all grittiness is gone and solution is uniform, let stand 5-10 minutes until microbubbles clear. Use within 30 minutes. Gives imagewise stain and general (fog) stain.
This works equally well with any "crystals" type instant coffee (after initial tests, the next time I bought coffee for this (I don't drink instant unless it's an emergency) I bought the cheapest they had at the supermarket that looked like Folger's Crystals. I gave 30 minutes at 20C for both the Tri-X that was fresh in 2003, and for Fomapan 100 (9x12 sheets).
Later, I learned about adding ascorbate:
8 oz. Water
2 1/2 tsp (level) Arm & Hammer Washing Soda
1 g Ascorbic acid or erythorbic acid (supplement or technical, 97%)
4 tsp (slightly rounded) Folger's Coffee Crystals
Mix as for Caffenol. Expect slight film speed increase (1/3 to 2/3 stop) and little or no stain.
The increase in alkali is to offset the acidity of the ascorbic acid; it's unnecessary if you use sodium ascorbate. I gave this only 12 minutes, but got more fog than with the original, and less imagewise stain.
Where I found coffee really shines is on microfilm stocks; I created Caffenol L(ow)C(ontrast)+C in 2005.
Caffenol LC+C (speed enhancing low contrast microfilm developer)
8 oz Water
4 tsp (level) Arm & Hammer Washing Soda
.26 g (4 grain) Ascorbic acid or erythorbic acid (supplement or technical, 97%)
2 tsp (slightly rounded) Folger's Coffee Crystals
Use with microfilms to give increased speed with pictorial contrast. No detectable stain.
If you're not equipped to measure sub-gram amounts of ascorbic acid, you can mix 1/4 tsp in a quart of water and use 8 ounces of that to mix the developer. I gave this 15 minutes at 20C, agitating only every 3rd minute; I got EI 50-64 with Copex Rapid and EI 20 with original Adox CMS 20, but with good dynamic range and pictorial tonality (but still with the extreme fine grain and sharpness characteristic of those stocks). MUCH cheaper than H&W Control, though about 1/3 stop lower film speed.