pyrocat hd question for Sandy King, Bud at Formulary?

Discussion in 'B&W: Film, Paper, Chemistry' started by climbabout, May 9, 2008.

  1. climbabout

    climbabout Member

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    Related to the recent pyrocat thread, I did not want to hijack it so I started this thread. I've been using Pyrocat HD from the formulary - the A and B solution mixed in water and I'm going to get my next batch from them in Glycol. I generally use a 1.5A/1.0B/175 h2o mixture, so I have quite a bit of the B left over when I run out of A. Can I use the A in Glycol and mix it with the leftover B that's in water? or should I dump the B that I have?
    Tim
     
  2. Fred Aspen

    Fred Aspen Member

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    I think I would dump B. I read that the water based solutions have a much shorter life than the glycol based solutions.

    Fred
     
  3. Formulary/Bud Wilson

    Formulary/Bud Wilson Advertiser Advertiser

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    Tim;
    Please reread my response to Fred in his thread about the Pyrocat MC.

    I cannot give a blanket statement that yes or no this is or isn't OK.

    I can't recomend that you mix a new solution with an older solution. The prudent thing is to use the proper A solution with the proper B solution.
    One of the advantages of Sandy King's formulations are the abiltiy to change dilution ratios, but this creates the disadvantage of having one of the solutions left over from an unbalanced ratio. Kind of a good news bad news thing.
    Just give it some thought, and weigh the pro and con. Is it worth saving a few cents worth of B solution and put a few dollars worth of film into it?

    I think we might call that stepping over dollars and picking up dimes.

    Bud Wilson
    Photographers Formulary
    Celebrating our 30th year
     
  4. climbabout

    climbabout Member

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    THANKS

    Bud - thanks for the reply - that's why I asked - when the A is gone, I'll replace both bottles with Glycol.
    Tim
     
  5. sanking

    sanking Member

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    Tim,

    I would have to say that it depends a lot on the age of the Stock B solution. Stock B is a straight 75% potassium carboinate solution that I mix in water, even when mixing Stock A in glycol. The reason is that the strong carbonate solution is very long lived. How long I really don't know, but at least a couple of years. It is really only the Stock A solution that benfits in terms of shelf life from mixing in glycol. In fact, I never even considered if the carbonate would go into glycol since it is already so stable in water.

    Maybe Pat Gainer will notice this thread and comment. He is really the brain behind the mixture of both Pyrocat-HD and -MC in glycol.

    Sandyd King
     
    Last edited by a moderator: May 9, 2008
  6. Tom Hoskinson

    Tom Hoskinson Member

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    Sodium and Potassium carbonates are not soluble in glycol. Both are readily soluble in water.

    I mix my own Pyrocat MC and HD from scratch:

    I use Propylene Glycol as the "A" solution solvent (keeps for years: 3+ and counting).

    I use DI Water as the "B" solution solvent (keeps for 2+ years).


    However, in principle, you could use TEA (Triethanolamine) as an organic source of the alkali.

    This would require testing.
     
  7. tony lockerbie

    tony lockerbie Subscriber

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    Sorry, but I'm going to hi-jack this thread a little! I mix my part A in water, what is the life span of this in a partly filled brown glass bottle?
    So far I have had it mixed for around 4 months and pretty much develop everything in Pyrocat HD these days.
    Tony
     
  8. juan

    juan Subscriber

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    I kept Pyrocat HD mixed in water for about 9-months before using it up. I'd say 9-12 months is about the outer limit.

    As for B - I computed how much dry sodium carbonate to mix with the working strength developer so I don't actually mix a B solution at all.
    juan
     
  9. Eric Rose

    Eric Rose Subscriber

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    I had some that was over 2 years old that worked just fine. YMMV.
     
  10. sanking

    sanking Member

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    For practical work with partially full Stock A I agree with Juan. 9-12 months is a good limit for Pyrocat mixed in water. When I worked with Pyrocat mixed in water I would always add marbles to minimize oxidation. This allowed the original control solution that I mixed to be effective up to about 1.5 years, and would probably have been good for longer but I used it all up.



    Sandy King
     
    Last edited by a moderator: May 9, 2008
  11. sanking

    sanking Member

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    Tom,

    Thanks for this information. I was fairly sure that the carbonates were not soluble in glycol but appreciate your exact knowledge.

    I had not considered the possibility of mixing the carbonate B solution in TEA. Might be a bit overkill, but the though is interesting.

    Sandy
     
  12. Tom Hoskinson

    Tom Hoskinson Member

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    Just suggesting trying TEA plus water instead of Carbonate.
     
  13. sanking

    sanking Member

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    Tom,

    I am pretty sure that TEA + water will not work in place of carboante + water with any of the Pyrocats. Pyrocat needs a working pH of about 10.9 or higher. TEA gives only about pH 9.2 or so , much too low for active development with the Pyrocats.. This pH works fine with pyrogallol based reducers, but not with pyrocathecin/catechol reducers which need a much higher working pH.

    Sandy
     
  14. gainer

    gainer Subscriber

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    Tea is strong enough to use with PMK in place of the Kodalk solution. I have tested that. Diethanolamine might be strong enough to use with thr Pyrocats, but you'd have to experiment with the ratio. I don't see much need to use the organic base for the B solution. The water solution works and will last a long time.