Lifetime of Pyrocat-HD working solution

Discussion in 'B&W: Film, Paper, Chemistry' started by DeanC, Jun 6, 2004.

  1. DeanC

    DeanC Member

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    Does anyone (this probably means Sandy ;-)) know how long Pyrocat-HD lasts after mixing?

    I do all my film developing in Jobo expert drums and I'm wondering if it'll last long enough for me to mix up a big batch, develop, stop, fix, rinse one set of negatives, rince and dry the drum and then repeat on another set. If it will, how many sets can I reasonably get through? With the small quantities of sols. A & B involved (even at 2:2:100) it seems it would be easier to accurately mix up a batch that is a litre or two in size than to mix a few that are each 200-500ml.

    Thanks,
    Dean
     
  2. Donald Miller

    Donald Miller Member

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    I develop my film in BTZS type tubes with minimal agitation. That means that I have a large volume of developer in an 8X10 tube. My experience indicates that I can develop 3 negatives with the same developer reused. This often amounts to over two hours of combined development time when I am developing a SBR 5 or SBR 6 negative. 10 oz of working solution Pyrocat at 1-1-100 will accomodate an 8X10 negative. The 1-1-150 (minimal agitation) and 2-2-100 Azo or Pt dilution should certainly have the same capacities. Hope that this answers your question.
     
  3. philldresser

    philldresser Subscriber

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    I have mixed a batch (500ml of 1:1:100) and had to leave it standing in a closed bottle for 2.5 hours with no depreciation in quality. The liquid did discolour slightly (tan) but still worked fine.

    Phill
     
  4. philldresser

    philldresser Subscriber

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    Just for interest sake my Pyrocat-HD stock solutions have given up the ghost but lasted 8 1/2 months in sealed medicine bottles. These bottles were opened at least once per week for removal of liquid. Worked fine last week but completely dead this week with only approx 10ml left.

    Phill
     
  5. roy

    roy Subscriber

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  6. sanking

    sanking Member

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  7. philldresser

    philldresser Subscriber

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    Roy

    I ran half an erroneously exposed sheet of 5x4 in a btzs tube. Came back very clear indeed. Mixed up a new batch and ran the test again and it was very black indeed. Not very scientific I'm afraid

    Phill
     
  8. philldresser

    philldresser Subscriber

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    Sandy

    My solution A was a light brown and produced no density at all on a fully exposed sheet of 5x4 (1:1:100@20c 8.5min). A fresh batch worked fine. Could it be that I put 2x solution B or A in the mix ? I am usually quite methodical with chems but I did mix up a batch in my fixer last week. Fortunatly I saw the error.

    Phill

    PS I was quite impressed with the 8.5 months
     
  9. sanking

    sanking Member

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    Phil,

    If you put double B or A in a working solution I doubt you would be the first person to do that. I am dumb enought to have killed more than one good negative that way.

    But I suspect that may have happened in your case if you got absolutely no devloper action from the mix. A light brown mix suggests that oxidation is taking place and would probably give weaker results, or perhaps more staining, than a clear solution, but I don't think it would be totally dead.

    Sandy
     
  10. gainer

    gainer Subscriber

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    As Sandy said, if you can't use it before it spoils, mix it in propylene glycol instead of water. All you need is the phenidone and the catechol. The bisulphite is for preservation. Glycol does that. If you think you need sulphite for some other reason, add a little to the working solution or to the B solution. Don't use very much, or you will lose the stain. Phenidone and catechol with sulphite and alkali is not much different from an ordinary PQ developer. The working solution should have no more than about 1 gram for every gram of catechol. That much will assure the superaditivity of the catechol with the Phenidone.

    I find I can get good stain and tanning as well as good film speed without any sulphite.
     
  11. sanking

    sanking Member

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    Thanks to the results of Pat Gainer's research I have been mixing my Pyrocat-HD Stock A solution in propylene glycol for several months, with excellent results. Here is what I do for mixing one liter of Stock A.

    1. Measure out the necessary amount of pyrocatechin, phenidone, bromide and potassium metabisulfite that goes into the Stock A solution. For one liter of Stock Solution A that is 10g of potassium metabisulfite, 50g of pyrocatechin, 2g of phenidone and 2g of potassium bromide.

    2. Heat about 950ml of propylene glycol in a Pyrex container to 250-275 degrees F.

    3. Add the pyrocatechin and stir until it is completely dissovlved.

    4. Add the potassium metabisulfite and stir until completely dissolved.

    5. Add the potassium bromide and stir until completely dissolved.

    6. Check the temperature of the solution and make sure it is below about 150 degrees F. If it is not continue to stir the solution, checking the temperature from time to time until it falls to around 150 F.

    7. When the solution is at 150 degrees F or slightly lower add the phenidone and stir until completely dissolved.

    8. Top off to make a total of 1000 ml of Stock A.

    Be very careful when working with solutions at 250 degrees F and higher. Even a drop of a solution that hot anywhere on your body is capable of inflicting severe damage.

    I have tested solutions prepared this way against a comparison Stock A Solution mixed with water and the results were virtually identical with the film tested.

    So far I have not tested the A solution in propylene glycol leaving out the bromide and potassium metabisulfite, as Pat suggests, but plan to do so soon.

    Sandy
     
  12. Tom Hoskinson

    Tom Hoskinson Member

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    ...So far I have not tested the A solution in propylene glycol leaving out the bromide and potassium metabisulfite, as Pat suggests, but plan to do so soon.

    Sandy[/QUOTE]

    I currently mix the A solution in propylene glycol using only the phenidone and pyrocatechol. For mixing, I use a hotplate/magnetic stirrer combination with a calibrated digital thermometer immersed in the solution. The phenidone and pyrocatechol both dissolve completely between 140 F and 160 F. The potassium metabisulfite and KBr can be added to the B solution. I have tested this version of Pyrocat-HD against the original formulation and have seen no differences.