Other basic (as opposed to acidic) chemicals can be used in place of sodium carbonate, however sodium carbonate is the most common.
There are many formulas for caffenol. All are based on preparations which contain caffeic acid (i.e. coffee or tea) and a pH modifier, most often sodium carbonate. The chemistry of caffenol developers is based on the action of the reducing agent caffeic acid (which is chemically unrelated to caffeine).
The Technical Photographic Chemistry Class at RIT in 1995 led by Dr. Scott Williams developed a method of developing photographic film using standard household items. They tested mixtures of tea and coffee combined with agents to balance the pH and successfully made printable images for exposed film. At the time they did not call it "Caffenol", but the methods they developed later became commonly called Caffenol.
- Williams, Scott. "A Use for that Last Cup of Coffee: Film and Paper Development". Rochester Institute of Technology.
- Film Photography Project:Coffee Break – Develop Film at Home with Caffenol, Film Photography Project.[dead link]
- Formulas, Digitaltruth Photo.[dead link]