Once the desired degree of development has been
reached, the process must be stopped quickly to avoid
overdevelopment. This can be achieved through a
simple water rinse, but an acid stop bath is more
effective in neutralizing the alkaline activators and
stopping development almost instantaneously.
A dilute solution of acetic or citric acid makes
for a powerful stop bath. However, with developers
containing sodium carbonate, the acid concentration
must be kept sufficiently low to avoid the formation of
carbon-dioxide gas bubbles in the emulsion, because
this may lead to ‘pinholes’ in the emulsion.
in short, after conducting a proper film test, an acid stop bath is an efective way of using the test data and stopping development when we need to. thi avoids after developmentand confusing resultswith overdeveloped highlightsand unrealistic speed points. the question is not why/ it is why not?pinholes and air bubbles as a reaction with sodiun carbonate can also be avoided by using a half-strength stop bath for films.