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Film Stop Bath
How much glacial acetic per liter??
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1 ml / 100 is 1%, and 2 ml / 100 is 2% (approximately).
This should do for starters. stops range from 1 - 2%.
PE
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 Originally Posted by Photo Engineer
1 ml / 100 is 1%, and 2 ml / 100 is 2% (approximately).
This should do for starters. stops range from 1 - 2%.
PE
Thank you, PE. What dilution would you recommend for one shot use?
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Lensmagic,
That's already a working solution that he gave you. No need to dilute further.
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That dilute, it's actually weaker than the vinegar in your kitchen. I'm not sure there's a benefit to further diluting it, you could use it one shot as is. If you're buying glacial, you'll certainly have plenty.
Honestly, though, I'm not sure I'd bother --get some pH test strips, or indicator, and test it periodically if you're worried. It works by neutralizing the developer, so as it's expended, the pH will approach neutral. (pH of 7) At 2%, I'd expect it to start around a pH of 3...and I'd probably neutralize it with a little baking soda and toss it by the time it got to 5 or so.
If you really wanted to conserve, you could replenish it periodically as it got close to neutral, but water is cheap....
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Film stop bath is a fairly non-critical processing step. In addition to simply washing the no-longer-needed developer away, its function is to neutralize the alkaline developer quickly and brings development to a complete stop. As msa said, the latter is achieved as long as the pH is below '7'. The former can be accomplished with a alternative water bath.
Some practitioners are concerned about the formation of unwanted gas bubbles in the emulsion, which possible with film developers containing sodium carbonate. This is less likely with a weaker stop bath (1%) and can be prevented with a preceding water rinse (in addition to or as a replacement for the stop bath).
Using stop bath one-shot, monitoring its pH or using a water stop bath instead are all possible scenarios, and you'll find supporters for all of them, but process consistency is more important than the difference between these options.
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There are still some things I don't know exactly, maybe some of you can clarify these issues:
In rare cases film manufacturers recommend a very weak stop bath or to use water instead. I can recall such a recommendation for Efke films, but that might be outdated.
I remember that for some types of fixing bath an acetic stop bath is mandatory, for the "odorless" alkaline fixers I don't know what is the best solution.
I use citric acid to avoid the penetrating odor of vinegar in my tiny darkroom. How much would you use per liter, and how long would you use it, e.g. for how many films or how much paper?
In some cases the stop bath developed a lot of foam, and when opening a film developing tank there was a smell like acid. It happened a few times, I used XTol and citric acid, probably too much acid. There are some commercial stop baths that contain extra ingredients to stop this kind of smell, what could that be?
The future belongs to the few of us still willing to get our hands smell like fixing bath.
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Nothing is easy.
Originally Posted by cmo
... In rare cases film manufacturers recommend a very weak stop bath or to use water instead. I can recall such a recommendation for Efke films, but that might be outdated. ...
As far as I know, it's more a recommendation for developers that contain significant amounts of sodium carbonate, because in combination with an acid stop bath, this can create air bubbles and 'pinholes' in the emulsion.
Originally Posted by cmo
... I remember that for some types of fixing bath an acetic stop bath is mandatory, for the "odorless" alkaline fixers I don't know what is the best solution. ...
It's not mandatory for acid fixers. It's sometimes recommended with alkaline fixers. The concern there is that a plain water bath will not stop development quickly enough. Again, consistency is the key.
Originally Posted by cmo
... I use citric acid to avoid the penetrating odor of vinegar in my tiny darkroom. How much would you use per liter, and how long would you use it, e.g. for how many films or how much paper? ...
No matter which of theses acids you use, you need a 2% solution. Feel free to reduce it to 1% if you experience pinholes in your film emulsion.
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Citric acid contains three carboxylic groups while acetic acid has one. Citric acid has a greater molecular weight than acetic acid. When all this is considered you would need a 1.5% solution of citric acid as a stop bath for films and papers. Dissolve 300 g of citric acid in enough water to make 1 liter of solution. Dilute 1+19 for use.
It's best not to try to reuse citric acid stop baths because they tend to grow mold very quickly on storage. The concentrate given above will keep since its high osmotic pressure kills many micro-organisms,.
A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.
~Antoine de Saint-Exupery
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The larger the format, the more critical is the use of a stop bath or very strong agitation in a running water rinse bath after development. This is to avoid any chance of nonuniformity.
The pinhole problem due to carbonate developers and soft films has been a non-issue with most films on the market since the 50s. In fact, George Eaton's book of that era is the last mention of pinholes, and even that was restricted to deep tank processing in which hydrostatic pressure prevented the release of CO2 as it formed. It formed at one time, as the film came up out of the deep tank. So, this is not likely with products from Kodak, Ilford and Fuji. It may be an issue with other products.
PE
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