Quote Originally Posted by Akki14 View Post
Coffee developers tend to be staining (unless you add vitamin c) and pull developers and they take forever (30minutes at least) to develop film. It's a neat trick but I'm not sure I'd like to use it all the time. Basic recipe is just instant coffee, washing soda (calcium carbonate), and water and the starting amounts are on digitaltruth's technical data section.
Washing soda is sodium carbonate with a bunch of water of crystallization. Calcium carbonate is limestone which would probably work as filler to take up airspace in a developer bottle, or to pave your driveway. Just a slip of the periodic table, I expect.