I am about to use the following Adostop Eco concentrate. I have two questions:

  • It's stated there for film it requires 30sec. What time does it refer to? Agitation?
  • Can we reuse the stop bath after we make the 1+19 solution? If yes, how can we know when to discard?

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1 Answer 1


The 30 seconds is "wet time". In other words, you pour in the stop bath (or dunk the film in), this stop bath solution for 30 seconds (time in this solution is not critical). This Adox stop is an indicator stop. In other words, this solution contains an indicator dye that changes the solution to blue (indigo) when exhausted.

The rest of the story -- Development takes place in an alkaline environment. A stop bath solution is mildly acid. Once film is plunged into the stop bath, development is arrested. The working solution can tolerate numerous rolls of film. After a time, the acidity of the working solution will become contaminated by developer fluid riding piggy-back on the film being processed. The dye indicator of this stop bath formula is akin to the litmus paper test strips used to measure the pH of solutions. When sufficient developer carryover has naturized the working stop bath, it changes its color from pink to blue (indigo). This is your signal that the stop bath is exhausted.

  • \$\begingroup\$ thanks a lot. So you can reuse this stop bath right. \$\endgroup\$
    – neversaint
    Jul 6, 2019 at 14:49
  • 2
    \$\begingroup\$ @neversaint yep. Mix up a batch. Use it. Pour the batch back into its container. Use again, and again, until it turns blue-ish. \$\endgroup\$
    – OnBreak.
    Jul 6, 2019 at 15:02

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