Certain reusable solutions are potent enough to not be exhausted after a single use. Depending on the activity of the processing agents and chemistry dilution, it is simply a matter of extending processing times to compensate for the weakened chemistry.
Df96 Monobath and Blix Reuse:
With self-completing chemistry, like Df96, Bleach & Fix, etc., you can err on the long side rather than too short. You can simply start with much longer process times or recombine each liter of used chemistry and extend the process by at least 5% for each roll previously processed. If a film does not appear fully cleared, process for longer in Df96. It will not affect development.
Cs41 Color Developer Reuse:
Whenever reusing color developer, combine all used and unused color developer to make 1000ml of weakened developer solution then add 2% to the recommended development time for each 135/120 roll, 8x10 sheet and every four sheets of 4x5 previously processed.
From the user’s viewpoint it may seem that chemistry manufacturers are somewhat arbitrary about the number of films which can be processed before the chemistry must be discarded. This stems from the manufacturer not knowing - only guessing - four essential things: how many films will be processed in freshly mixed chemistry; in what manner and how long will the chemistry be stored before processing again; what contaminants have entered the system from either the water supply or from unintentional chemical intermixing; and how far can the results deviate from ideal before the user deems them unacceptable.
If you take full responsibility for quality of results, it is possible to process more film over a much longer time span. This procedure is somewhat risky unless you process some film every day or so to monitor chemistry performance. Otherwise, partially used working solutions left untouched for a week or more might have changed so significantly that you would suffer a dramatic decline in results. If you choose to operate under these conditions, our best advice would be to process a small piece of test film, and on the basis of these results, decide whether or not to commit valuable pictures to the chemistry. At the end of the day, there is only one rule in this exercise: process film until you no longer like the results.
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