Stop bath

Stop bath

Stop bath is the second of three chemical baths usually used in processing traditional black-and-white photographic films, plates, and paper. The sequence is: developer, stop bath, fixer. The purpose of the stop bath is to halt the development of the film, plate, or paper by either washing off the developing chemical or neutralizing it. With the former, a simple water rinse can be used between developer and fixer, but the development process continues (though possibly at a very low level) for an indefinite and uncontrolled period of time during the rinsing.

Where an immediate stop of development is desired, a stop bath will usually consist of some concentration of acetic acid, commonly around 1 to 2%. By neutralizing the alkalinity of the developer, stop bath halt the development process almost instantly and thus provides more precise control of the development time. It also cuts overall processing time, because the required immersion time in the stop bath—typically fifteen to thirty seconds—is much shorter than the time required for an adequate plain-water rinse. As well, by neutralizing the alkalinity of basic developers, it can help to preserve the strength of the fixer, making it last longer.

Stop bath accounts for the characteristic vinegar-like odor of the traditional darkroom, and in its concentrated form can cause chemical burns. For "indicator stop bath" -- a stop bath that changes colours to indicate when the stop bath is exhausted and no longer effective -- the pH indicator bromothymol violet is used to determine when the solution has become too alkaline to use. Low-odour stop baths use citric acid or sodium bisulfite in place of acetic acid.

ources and notes

* [ Black & White Film Developing]
* [ Odourless stop bath]

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Look at other dictionaries:

  • stop bath — stop′ bath n. pht an acid bath or rinse for stopping the action of a developer before fixing a photographic negative or print • Etymology: 1915–20 …   From formal English to slang

  • stop bath — n. Photog. a weak solution of acetic acid used to stop development of photographic prints or film before fixing …   English World dictionary

  • stop bath — noun an acid bath used to stop the action of a developer • Syn: ↑short stop, ↑short stop bath • Hypernyms: ↑developer * * * noun : an acid rinse bath between a photograph developer and the fixing bath used to check development of a negative or… …   Useful english dictionary

  • stop bath — /ˈstɒp baθ/ (say stop bahth) noun (in photography) a bath of weakly acidic solution into which films, etc., being developed are immersed to stop the action of the developer …   Australian-English dictionary

  • stop bath — Photog. an acid bath or rinse for stopping the action of a developer before fixing a negative or print. Also called shortstop, shortstop bath. [1915 20] * * * …   Universalium

  • stop bath — noun Date: 1898 an acid bath used to check photographic development of a negative or print …   New Collegiate Dictionary

  • short-stop bath — noun an acid bath used to stop the action of a developer • Syn: ↑stop bath, ↑short stop • Hypernyms: ↑developer * * * noun see short stop …   Useful english dictionary

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