What is the purpose of stop bath? (Regards to Film)

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What is the purpose of stop bath, and what will happen to your film if you don't use it during the development of Film?

-- Keith V. Polischuk (Kpolischuk@yahoo.com), April 18, 2001

Answers

The purpose of a stop bath is to quickly inactivate the developer by changing the PH. This allows more precice development times. Also, this will cause your fixer to last longer.

If you do not use a stop bath, nothing will happen. Many photographers do not use it and some developers (Pyro for example) work better without it.

-- Ed Farmer (photography2k@hotmail.com), April 18, 2001.


Keith:

An acid fixer will stop the chemical reactions of the developing agents the same way an acid stop bath does. As a matter of fact, in an old darkroom instruction book that I have, acid fixers are referred to as "stop-fixers". If some sort of stop bath isn't used, however, problems can arise. Excessive developer carry-over can cause stains, and changes in the pH level of the fixer can reduce the fixer's effectiveness.

If an acid stop bath isn't used, it is still wise to use a water rinse between developer and fixer. It would also be wise to moniter the pH of the fixer as well as periodically check film clearing times. For large-volume work, it might be necessary to replenish the fixer periodically.

-- Ken Burns (kenburns@twave.net), April 18, 2001.


An acid stop bath can cause pinholes in the film if used following a developer high in carbonate (such as Paterson developers and other high acutance formulas). The safest thing is to use a water rinse before the fixer. I fill the tank three times and agitate for about 10 seconds each.

-- Brian Hinther (BrianH@sd314.k12.id.us), April 19, 2001.

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