Response to stop bath?: water vs. stuff-you-pay-for

Most developing agents require an alkaline environment to be able to operate (amidol is the one exception that proves the above rule). A stop bath like acetic acid changes the pH in the print to acidic very quickly and basically arrests development very rapidly. In addition, by neutralizing the developer, it is supposed to extend the life of the fixer (since the fixer does not have to neutralize the developer). Having said that, a water rinse works very well too - its just not a sudden stop the way an acidic stop bath is. Water dilutes the developer a lot pretty quickly but since the pH is probably neutral or mildly alkaline, there probably is some additional activity which will continue to take place. There are reasons you might prefer one or the other. Typically, a lot more folks seem to use a plain water stop in film development. With paper development, most people seem to prefer the acid stop. However, there are some folks who use a water stop even for paper (as long as you are consistent, you won't go too wrong since the marginal additional activity in the water stop bath can be adjusted by pulling the print from the dev just a smidgin earlier). Note that the most important criterion is how quickly you need to stop development. In lith printing, for example, you are developing by inspection and need to arrest development very rapidly (since we are talking about infectious development there). So, there's no way around an acid stop bath there. Good luck, DJ.

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