Foma Fomacitro Stop Bath is a liquid concentrate, citric-acid based, odorless stop bath with indicator. It is designed for processing all black and white photographic films and papers.
Dilute with water (1:19) for a working strength solution. Stopping time is 10 - 20 sec for film and RC papers, and 30 sec for fiber-based papers.
A color change of the working solution from yellow-orange to blue-green lets you know that the bath is exhausted and should be exchanged for a fresh one.