Ilford ILFOSTOP is a low odor, citric acid stop bath which stops further development of paper or film. It also prolongs the life of the fixer bath, maintaining the activity of your fixer solution, by neutralising the developer.
Ilford recommends that all black & white darkroom papers and films are rinsed in ILFOSTOP after development, especially when dish/tray processing paper or deep tank processing film.
This bottle of ILFOSTOP contains 500 ml of concentrate which makes 10 liters of working strength solution.
The Brownie Camera Guy says:
Ilford makes the highest quality analog photographic products available!