Pmk stain on rebate

Discussion in 'B&W: Film, Paper, Chemistry' started by ann, Jul 14, 2003.

  1. ann

    ann Subscriber

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    I have been playing with PMK for a month or so. The first few rolls were HP5+ , 35mm that had been in the fridge for awhile and out of date. The rebate stained as well as the exposued sections. I wasn't aware that that would happen and when checking around was told that it was due to the out of date film. No problem, negatives printed fine. Another up todate roll developed without staining the rebate.
    Tonight I developed several rolls of Hp5+ , 120 with out of date of 2005. Rebate staining again. The negatives appear fine and will probably print fine.
    Just wondering about the rebate stain. Is this a normal condition.? i am not going to lose any sleep over this, just wondering what is going on.
     
  2. Donald Miller

    Donald Miller Member

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    PMK developer is advertised and widely recognized as developing general stain. If you will look at any of the Bergger-PMK ads in the magazines it is readily apparent. I personally don't think that general stain is a wonderful attribute since it decreases negative contrast. I much prefer other pyro formulations such as ABC or Pyrocat HD. The reason that I prefer those formulations is that they do not develop general stain in the same way that PMK does. The stain that the ABC and Pyrocat HD formulations develop is proportional to the negative density. The effect of the proportional stain is to increase negative contrast with greater mid and high value separation.
     
  3. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member

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    The alleged advantage (I'm not entirely convinced of this, but I haven't done a definitive test) of the general stain with PMK is grain masking, since pyro is by nature a grainy developer. Read Gordon Hutchings' _The Book of Pyro_ for all the details.

    If you want to decrease the effect, don't do the pyro or sodium metaborate afterbath following the fixer and reduce your wash time to 10 minutes instead of 20-30 minutes recommended to increase the stain.
     
  4. sanking

    sanking Restricted Access

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    My opinion is that the grain masking you get with proportional stain is a very good thing because it is a stain clustered around the silver particles. General stain is garbage because it does absolutely nothing to enhance print values, and may in fact detract from them by limiting the contrast range of the negative. Often you can just print through general or base stain, but when using high speed films like Ilford HP4+ in very flat lightiing situations the stain may actually prevent you from getting enough contrast. This is because there is a finite CI to which a film can be developed and the log value of general or base will subtract from that value one to one.

    However, it is perfectly natural to get a fogged rebate with outdated films or with films that have been prematurly fogged by heat, even when usisng staining developers that produce only proportional stain. The stain reacts proprtionally to the built-in fog just as if the high b+f level had been created by light.

    There is really nothing you can do to eliminate staining of the rebate with outdated film but you surely should follow David Goldfarb's advice and avoid the alkali afterbath. I personally think the alkali afterbath is very bad practice even with fresh films but at least with films that have a low b+f to begin with the afterbath does not do a great deal of hard. And that is about the best thing I will say about the afterbath.

    Sandy King
     
  5. ann

    ann Subscriber

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    thanks to all. The contrast of the negatives is fine, just thought it was interesting that some on some of the film the rebate becomes stained on others it did not (same film type).
    I am using Gordon's instruction as found in his book on Pyro.

    Research as shown many folks forgo the bath after fixing. I might give that a try and compare the negatives when printed.