FP4 in Nescafe and Detergent

that IS pretty interesting! I wonder what it is that actually "develops" the emulsion?

The best guess I've heard is caffeic acid and/or its progenitor, chlorogenic acid. Both are present in coffee (caffeic is produced primarily in drying and roasting the beans), and both are catechols, chemical relatives of pyrocatechin. Caffeine has been ruled out; No-Doz tablets will not develop film at all. The resulting negative has an imagewise stain similar in character to that produced by pyrocat, though some emulsions, like Tri-X, also pick up a strong general stain (i.e. fog) probably due to tannins and lignins in the coffee. My experience has been that Tri-X, even though it looks quite foggy after processing with Caffenol, still scans well. It should also be noted that the stain will print more strongly than it scans, and that Caffenol negatives that print well are likely to look a little thin to the eye.

I wonder if regular coffee would also work or does it have to be the instant stuff? Also, if the magic is in the roasting, would dark roast coffee give different results from those of light or medium roast beans? Very interesting.....

Regular coffee probably would work but I hate to think how much you'd have to use. I was putting 6 teaspoons of instant in just 12 oz of water, it would have made for one STRONG cup of coffee.

This has been tested -- regular coffee *does* work, but it needs to be very, very strong. The mix with instant is about 3-4 times normal drinking strength, so with regular coffee it's closer to espresso than any drip brew (of course, the oils in espresso will also cause problems). And of course instant is a lot cheaper than espresso, even if you have your own machine.

I don't know about other variables -- someone in Germany reported that a locally available instant, marked (under very strict German food labeling laws) as 100% arabica, required 50% more coffee to produce the same effect in the same time. Most American instants have a substantial fraction of the cheaper robusta beans, which have lots of caffeine but don't make coffee that tastes as good (they're larger, and very hard to roast evenly -- by the time the core of the bean is roasted, the outside is starting to burn), and it's very reasonable to suspect that the difference in species makes as much difference as a change in roast.

What would be more conclusive would be to obtain or extract reasonably pure caffeic and/or chlorogenic acid (the latter is found in almost all green plant parts, I gather), or at least get good assays of the quantities of those suspected developing agents in various varieties and roasts of coffee beans and various brands of instant.

Give it a go with a large Caffe Latte

Jokes aside; It is great fun using instant coffe for this...