Uneveness blacks in reversal process

Discussion in 'Color: Film, Paper, and Chemistry' started by 59gilbert, Nov 17, 2013.

  1. 59gilbert

    59gilbert Member

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    I recently tried B&W reversal processing. I found the same problem I had with E6. The unexposed area (black) appear slightly uneven, and sometimes with slight flow marks. I supposed this was formed during one of the fast acting processes, as it takes time for the chemical to get evenly in contact with the film. Am I correct? And, which process would that be? Reverse, or bleach? The bleach I used for B&W is dichromate.

    Thanks!
     
  2. Alessandro Serrao

    Alessandro Serrao Member

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    Can you describe more in detail your process please?
     
  3. Rudeofus

    Rudeofus Subscriber

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    My suggestion is, that you break down your process to see which step introduces the unevenness. If you do only the FD step and then fix right away, you have a (more or less) proper negative that you can enlarge, any unevenness from the FD step should show up right there. Bleach is a process that runs to completion and should not cause these problems. If you get proper negatives but your positives still show unevenness, in all likelihood you have issues in the second dev step.

    One thing that worked wonders when I had unevenness was a stop bath after each dev step, or at least make the "pouring out" as fast as possible.
     
  4. stefan4u

    stefan4u Member

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    The anti halation layer (mostly colloidal silver) in bw reversal films will require the dichromate/permanganate bleach step, or the result will be more like black in black…

    The answer may be included in the question, “flow marks” sounds like a problem with the agitation. Probably too intense agitation in order to compensate the “no agitation time” during filling or pouring out the drum.

    Regards stefan