Chemistry: Stop Bath
Using a chemical stop bath is frowned upon in some photographic circles. The argument is that the acidic stop bath may burn pin holes in the emulsion. Well. Pardon me. The alternative to a chemical stop bath is to use water, diluting the developer. This does not stop the action, but rather slows it. Using a rinse seems risky at best. You are betting your film against water quality, the solubility of the developer, and your ability to get enough water in and out of a tank. A chemical bath neutralizes the developer pretty much immediately, and properly mixed, should present no danger to your film (or paper).
What Stop Bath Does
As mentioned above, stop bath, a weak acid, chemically neutralizes developer, which is alkaline, or a base.
What Stop Bath(s) Is (Are)
Most commonly stop bath is acetic acid, which is commonly referred to as vinegar. It is not, however, suitable for use in salads.
Stop bath may contain an indicator, or a chemical which changes color as it is exposed to developer. Indicator stop will go from a bright yellow when mixed to a working solution from concentrate, to clear, then purple-blue when exhausted.
