![]() With prints, I process no more then 75 prints in 1 gallon of fixer. With films I develop no more than 7 rolls of film in one quart of fixer. Finally, the stop bath extends the life of the fixer. That level of precision lets me isolate other problems. not 2 minutes and 10 seconds or 20 seconds. If I develop something for 2 minutes, I want 2 minutes. Getting to the question, I use a stop bath because it halts the developer. I only use FB paper so I don't know the impact on platic resin coated papers. Reticulation is caused more by the difference in the temperatures then any other source. Stop Bath is discarded after every film or print developing session. I am very careful to make sure that the stop bath and fixer are all +- 3 degrees from the developer. I dilute stop bath for films 1:31 with 2% acetic acid. I don't use indicator stop bath because I don't trust it. ![]() This may be a scientific truth, but I have been using 2% acetic stop bath for 20 years and I have not reticulated a film or damaged an emulsion. The cost is so low that I make a new one for every session. In the one case where I do use a stop, I use about 10g citric acid (supermarket grade) in one liter of water. If you are really worried about damaging the fixer I will suggest doing without the stop altogether, and replace the fixer as soon as it is visibly brown. Adding alkali to an acid fix will neutralise the pH, but not the thiosulfate! I also use alkaline fix (again: For everything except lith printing), so there is no reason to change the pH from alkaline to acid before the fixer.įurthermore: pH has very little influence on the activity of the fixer. Paper is developed to conclusion (which it should be in all cases except lith prints), so any developer action in the "stop" - or even the fix - is irrelevant. In that one case it is important to stop development immediately at the right point, and nothing does that as well as an acid stop.įor everything else I use plain water. The only time I use an acid stop is when lith printing. But more importantly, stopping the development action abruptly makes it easier to tone the finished print - if you use a plain water stop, toned prints may have a mottled appearance since the duration of development will affect the visual appearance of the toned finished product. Paper is much more foregiving that film and can put up with the "abuse". A plain water stop cause the development action to "coast" to a stop - that's fine when developing film, and may actually be advantageous. That way I know when it's nearing the end of its useful life.Īnother reason for an acid stop is that it brings the development action to a rapid conclusions. Fixer life is very important when printing because it's so easy to lose track of how many sheets of paper have gone through the bath.įor this reason, the stop that I use in printing is also an indicator stop that changes color when it approaches a neutral pH. Using an acid stop minimizes this effect and makes the fix last longer. Then, when you move the print to the fix, the collision between base and acid results in the fix being neutralized. If you use a plain water stop, it will quickly become a weak base. ![]() There are several reasons for this.įirst, one of the main reasons for a stop is to provide a means of adjusting the pH of the film between developer and fix. I also tend to use water as a stop in dveloping film, but an indicating acid stop when printing.
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