Stop bath

Stop bath is an acidic solution used for processing black-and-white photographic films, plates, and paper.

[1] Stop bath is commonly a 2% dilution of acetic acid in water, though a 2.5% solution of potassium or sodium metabisulfite works just as well.

Neutralizing the alkalinity of basic developers also helps to preserve the strength of the fixer, making it last longer.

[citation needed] Stop bath accounts for the vinegar-like odor of the darkroom.

In its concentrated form it can cause chemical burns, but is harmless when diluted to a working solution.

A black and white photographic print in a tray while being processed after exposure to light under a photographic enlarger. Typically three trays are used containing either developer, stop bath, or fixer, in that order. The print must then be rinsed in water to removed the fixer.