So...wait...I"m not even a darkroom junkie, and I've heard of something you two HAVEN'T? Whoa. Don't remember what I heard about it or when, or where...but I do know I'd heard that. Could have sworn it was right here in this very forum.
I did this experiment with coffee about two years ago, the negative came out very light, but with some extra work scanning & in PS they looked good (different), unfortunately I recent deleted them for my PBASE site for the space.