Three Pyrocat HD/PMK Questions

Discussion in 'B&W: Film, Paper, Chemistry' started by jtsatterlee, Nov 9, 2004.

  1. jtsatterlee

    jtsatterlee Member

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    1. Does Pyrocat HD require the the 'long' washing times, similar to PMK (30+ minutes)? Or is the standard 10/15 acceptable?

    2. What is the shelf life of open containers of Sol A and Sol B?

    3. Any preference/recommendations between Pyrocat HD or PMK for HP5+ 35mm that will may be enlarged to 11x14, perhaps larger? (yes, I know that is stretching 35mm a bit)
     
  2. Eric Rose

    Eric Rose Subscriber

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    1. I use 15 to 20 minutes, but that is the same times I use with HC110 too.
    2. I have used sol's A&B that were at least 1 year old with no problems.
    3. I have found PC-HD to give me very nice 11x14's from 35mm. I've never used PMK.
     
  3. philldresser

    philldresser Subscriber

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    jtsatterlee

    1. I have found Wash times of 10-12 mins and a HCA bath for a few mins is sufficient on FP4
    2. A solution lasted me 10 months - B will last indefinitely I believe
    3. Same as Eric 11x14 from FP4 in 35mm are no problem with Pyrocat

    Phill
     
  4. bmac

    bmac Member

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    How are you guys sure a 10-20 min wash is enough? I wash at least 45 mins in an archival washer (sheet film).
     
  5. philldresser

    philldresser Subscriber

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    Brian

    I'm not sure that i,m sure but I am following the dev instructions from Sandy King where he states :

    Presoak film for two minutes. Use a plain water stop bath for one minute. Use an alkaline fixer (rapid fix without hardener) for 5 minutes. Wash in running water 10-15 minutes.

    Admittedly I sometimes wash for longer (normally while I am developing the next film/sheet) but I add the HCA wash as well and then rinse for a further 5min.

    Phill
     
  6. Tom Hoskinson

    Tom Hoskinson Member

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    With film a 15 - 20 minute wash after fixing in a non-hardening fixer should be adequate. Except for the initial rinse off, film washing is primarily a diffusion process, so washing in multiple water changes is a very effective and water efficient washing method.

    If you are not certain that you have gotten the fixer out of the film, perform a residual fixer test after washing.
     
  7. sanking

    sanking Member

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    Films need much less wash time than papers because all of the chemicals that need to wash out are right on the surface in a thin layer of gelatin. However, wash time is less important than the total number of changes. Ilford, for example, recommends a system that is based on twenty changes of water, without any running water at all. However, with a good flow of water entering at the bottom of a tray and leaving at the top you should easily get more than 20 changes in a 10-15 wash.

    As for shelf life, Solution B lasts indefinitely. Solution A, in a container that is at least half full, should be good for up to a year. If you need longer shelf life consider mixing Solution A using one of the glycols or glycerin, as Pat Gainer has suggested. I have mixed the Pyrocat-HD Stock A solution in both propylene glycol and glycerin and the results were identical to mixing in water. Stock A mixed in either glycerine or glycol will have a shelf life of years and years. If you are interested in this mix as follows.

    1. Heat the glycol or glycerin to 250º F. A liter of either solution heats to this temperature in about one minute in my microwave.

    2. Add the chemicals to the solution at 250º F in this order: First, pyrocatechin, then sodium metabisulfite, and then bromide.

    3. Allow the solution to cool to about 150º F and then add the phenidone. The phenidone will break down if added to the solution when it is over 200ºF.

    Sodium metabisulfite is used in the Stock A solution when mixed with water to acidify the solution and it functions as a preservative. It also reduces staining slightly because when mixed to form a working solution plain sodium sulfite is formed. You obviously don't need it in glycol or glycerine as a preservative and some people, Tom Hoskinsoin being one of them I believe, have simply omitted the sodium metabisulfite with the glycol solution and report good results with apparently no additional staining. I have never gotten around to testing staining with and without the soduim metabisulfite in the solution mixed with glycol so I am still adding it when just as I do with water. It may not be necessary, as Tom reports, but then again so little is needed and my current supply of sodium metabisulfite should last for at least two more decades, so what the hell!!

    Another variation is to add the bromide to the Stock B solution rather than put it in the Stock A. This will make no practical difference so long as the ratio of Stock A to Stock B in the working solution is 1:1. This may be a better solution since bromide is hard to get into solution in glycol, even at 250º F.

    Be very careful when mixing solutions over 250º F. A spill on the skin at this temperature can do great damage, as you might well imagine.

    Sandy
     
    Last edited by a moderator: Nov 11, 2004
  8. jtsatterlee

    jtsatterlee Member

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    thanks to all for the information
     
  9. fhovie

    fhovie Subscriber

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    I have used both PMK and Pyrocat and I would recommend only Pyrocat for 35mm if you wish to use a staining developer for this format. I have not been happy with staining developers in 35mm - if you plan to enlarge past 5x7. I would prefer a "fine grain" solivent developer for 35mm for enlarging.
     
  10. DeanC

    DeanC Member

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    I just tried mixing up my first batch of Stock A in propylene glycol and ran into a slight problem. It seems that neither the sodium metabisulfite nor the bromide would dissolve completely for me. I heated the glycol to 250F on a stirring hotplate and added the chemicals in the catechol, sodium metabisulfite, bromide order. The catechol seemed to go into solution readily but the metabisulfite left clouds of undesolved reagent floating in the solution and I still have a couple of lumps of bromide in the bottom. I used 750ml of glycol, 50g of catechol, 10g of sodium metabisulfite, 2g of potassium bromide and 2g of phenidone and topped things off to 1000ml at the end.

    I'm going to try again tomorrow, I think, perhaps leaving out both the sodium metabisulfite and the potassium bromide. If I do that, will I still need to heat the glycol to 250F to dissolve the catechol?

    This may be a silly question, but... Will moving the bromide to the Stock B solution impact its storage life in any way?

    Thanks,
    Dean
     
  11. john_s

    john_s Subscriber

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    If the metabisulphite is left out of glycol solution A does it eventually affect the pH of the diluted developer? If so, could it be put in solution B along with the bromide?

    I ask this simply because of convenience. I use 2 pipettes with rubber bulbs to make up working solution in the bathroom after the kids have gone to bed, and it's quite quick. I'd rather not be adding a powder as well.
     
  12. sanking

    sanking Member

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    First, even though it takes a lot of heat and stirring to get the bromide and metabisulfite into solution, both will eventually go into solution with enough heat and stirring. If 250ºF does not work, heat the solution to 300º F and stir a few more minutes. And repeat if necessary. As for mixing order, add the bromide and metabisulfite first and stir/reheat/stir until both appear to be about 98% in solution. Then leave the solution along for a few minutes and allow it to cool down to about 170º F, then add the pyrocatechin and phenidione. I have mixed three or four different batches of Pyrocat-HD Stock Solution A in glycol this way and have always been able to get the bromide and metabisulfite into solution and if it works for me it must work for others as well.

    I don't really know how adding the bromide and metabisulfite to the C solution will affect the shelf life ot Solution B. Perhaps someone with a good idea of how these chemicals could be expected to interact with each other might comment.

    For silver printing using the 1:1:100 dilution it really makes no differnce if the bromide and metabsilfute is in Solution A or Solution B. However, for alternative printing where very long development times are sometimes needed to get enough CI some Pyrocat-HD users have found, and my own testing confirms this to be so, that less general stain is produced with asymmetric mixtures such as 3:2:100, 4:3:100 and 5:3:100 than with symmetric dilutions.

    Sandy
     
  13. Jim Chinn

    Jim Chinn Member

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    Sandy,

    Doesn't Pyrocatechin have a very low vapor point, something around room temperature? I seem to remeber a warning somewhere about being carefull about inhaling catechol before it goes into the solution. Once in solution the vapro risk is gone. The second time I mixed some I was at a friends darkroom and I believe i inhaled some as my vision became blurry and began to dim a few minutes after I was done mixing. The symptoms went away after going into the fresh air. This was consistent with the MSDS for Pyrocatechin.

    Anyways at home I now wear a repirator with proper filtration. However with an already low vapor point in adding it to a hot solution would you vaporize enough Pyrocatechin in the steam or heat above the solution in the brief second before it enters the liquid to affect the "potency" of the developer? Is it to small of an amount to make any difference?
     
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  15. sanking

    sanking Member

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    I don't know what a vapor point is. The MSDS data for pyrocatechin/catechol indicates that it has a vapour pressure of 1 mm Hg at 75 C and a vapour density of 3.8, whatever that means. The only personal protection recommended in the MSDS data is use of safety glasses and suitable ventilation. I have never experienced any physical problems when mixing pyrocatechin and I don't use a respirtor. I just make sure that the area is well ventilated and don't allow my face to come any closer than about 18" or so to the powder.

    As far as the possible impact on the potency of the developer that might result from vaporizing the developer I have seen none. I have tested film developed in Pyrocat-HD mixed in water, propylene glycol, and glycerine and there was absolutely no differnce in developer activity.

    Sandy
     
  16. DeanC

    DeanC Member

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    Thanks Sandy, I'll give it another try today.

    Also, just in case someone hasn't said it here lately, thank you for being the incredible resource for the analog photo community that you are. Hurry up and publish a book on this stuff so we can all go out and buy a copy, would ya? ;-)

    Dean
     
  17. Tom Hoskinson

    Tom Hoskinson Member

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    The metabisulfite and Potassium Bromide can both be added to the working developer during mixing if/as needed. My personal way of mixing is to put only the developing reagents in the propylene glycol. This lowers the mixing temperature of the "A" bath and keeps it non-ionic.

    I'm sure that the KBr can be added to the "B" solution with no problem. I don't think I'd do that with the metabisulfite (though it probably wouldn't hurt).

    I always have a bottle of 10% KBr handy, so it is easy to add to the working developer if I wish. Same with the metabisulfite.
     
  18. gainer

    gainer Subscriber

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    I think the purpose of the metabisulfite in the original Pyrocat is to provide an acidic preservative that converts to the sulfite on mixing with B. The acidity aids in the preservation but has no function in the working solution except to promote the synergism between phenidone and catechol. If that is the case, you could add sulfite to the glycol solution or to the working solution. There will be some loss of activity if you leave it out altogether, but there might be a slight increase in the stain image.

    These are things that I think Sandy has checked out.
     
  19. gainer

    gainer Subscriber

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    And winding up with my foot in my mouth is what I get for not going to the beginning of the thread.
     
  20. Jim Chinn

    Jim Chinn Member

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    Thanks for the response Sandy.
     
  21. DeanC

    DeanC Member

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    Okay, the second batch is in the process of cooling down enough to take the catechol and phenidone now. It looks like all of the metabisulfite and bromide went into solution but the liquid is cloudy/milky now instead of clear (but it doesn't appear to settle out when I stop stirring so I think everything is disolved.) Should I be concerned about the cloudyness or should I just finish mixing and give it a try on a negative once it's cooled?

    Thanks again,
    Dean
     
  22. sanking

    sanking Member

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    Just give it a try after mixing in the pyrocatechin and phenidone. Slight clouding at this point is not unusual.

    Sandy
     
  23. john_s

    john_s Subscriber

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    This figure for vapor pressure quoted by Sandy (at 167degF) is low. Also, if a substance can stand that degree of heating without chemical change and without evaporating, which pyrocatechol apparently can, then vapor at room temperature will be miniscule. However, fine particles of powdered chemical can still become airborne easily, hence the usual warnings about breathing it in or spreading it around.
     
  24. sanking

    sanking Member

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    Thanks, and I am working on a book. Takes time, though. Let's just hope that by the time we finish the book there will still be film!!

    Sandy
     
  25. DeanC

    DeanC Member

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    Just finished trying both it and the first batch from last night that had the solubility problem. Looks like all the metabisulfite went into solution overnight...

    Just eyeballing the two negatives (4x5 step wedges contact printed onto 4x5 FP4+) they both look identical and appropriately developed (2:2:100, 70F, 11min rotary.) I'll throw them in the densitometer when I get home from work tomorrow night to be sure, but I think I've got 2 good liters of Stock A. That should be enough to last me while, eh?

    Thanks for all your help,
    Dean
     
  26. john_s

    john_s Subscriber

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    Would plenty of time be a substitute for heating?