pyrocat (or other catechol dev.) without sodium metabisulfite?

Discussion in 'B&W: Film, Paper, Chemistry' started by phritz phantom, Jan 24, 2009.

  1. phritz phantom

    phritz phantom Member

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    i want to give catechol devs another go. either a catechol/glycin variation or pyrocat hd (again).i have all them chemicals ready, except the sodium metabisulfite. i'll order new chemicals soon, but it usually takes at least a month for them to arrive and i don't want to wait that long right now.

    would it possible to mix pyrocat without the sodium metabisulfite? i've read that the s.m. is only for enhancing the keeping properties of the solutions and has no relevance for the image tone.
    how quick would pyrocat without s.m. go off? and should i substitute it with a little sodium sulfite (not too much, i don't want to kill all of the stain)?
    and would i need a different b solution (which is less alkaline), for example carbonate instead of the hydroxide?
     
  2. sanking

    sanking Member

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    The major purpose of the sodium metabisulfite is to add shelf life. However, when mixed with water the metabisulfite becomes sulfite, which plays a role in developer energy or activity.

    You could add sulfite instead of metabisulfite in about the same amount to the stock solution. There is a conversion ratio that I have on hand somewhere but can not locate it now. However, for this use I think a 1:1 substitution would work ok.

    Sandy King


     
  3. phritz phantom

    phritz phantom Member

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    perfect. thank you.
    the b-solution stays the same too (s. hydroxide), i figure.
     
  4. sanking

    sanking Member

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    Sodium hydroxide will work fine as the B solution but I think potassium metaborate is a slightly better choice.

    Sandy
     
  5. gainer

    gainer Subscriber

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    Don't forget that Pyrocat HD can be mixed in glycol with ascorbic acid in place of metabisulfite. The major function of the sulfite is to make possible the synergism between phenidone and pyrocatechin. There is not enough to have a noticable effect on grain. The ascorbate serves the function of synergism, better in some ways than sulfite.
     
  6. sanking

    sanking Member

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    I started to mention that one could substitute the metabisulfite with ascorbic acid, but 1) forgot the substitution rate, and 2) was not sure how stable the stock solution would be if mixed in water. I gather the OP just wanted a mix that would last a most a few weeks, but not sure if the stock solution mixed with ascorbic (in water) would even last that long.



    Sandy King



     
  7. gainer

    gainer Subscriber

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    I don't know either. The ascorbic acid certainly has antioxidant powers, and lowers the pH as well, but the life and death of developers is a bit of a mystery to me. During storage, especially since it is not to be reused, I would think the antioxidant powers should not be much different from the bisulfite, but I'm not rich enough to guarantee so. My practice is to do a snip test before serious use. I would recommend the propylene glycol solution in any case. (Of course I would.) The glycol is not awfully expensive at The Chemistry Store.
     
  8. sanking

    sanking Member

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    Jeeezzz, I can not believe I wrote that!!

    What I meant to write was, "I think potassium carbonate is a slightly better choice."

    Sandy King



     
  9. gainer

    gainer Subscriber

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    I did find a combination of borax and sodium hydroxide that would serve as B solution for the Pyrocat developers. My motivation was the fact that my hard water makes lots of calcium carbonate when I use sodium or potassium carbonate. I looked up a standard buffer solution in the CRC handbook that would have pH the same or close to the carbonate. Now I don't remember the proportions, but it works well. I must have written it down, but it's just like things in my memory...they're all still in there, but I can't remember where.
     
  10. phritz phantom

    phritz phantom Member

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    i was looking at the formula for diXactol at the same time, so i got the sod. hydroxide and pot.carbonate confused.g
    but good that you mention the error with the metaborate, because after you mentioned it i dug out the bottle of sodium metaborate which came as the b-solution in a pyrocat-hd package i ordered from lotus in austria years ago.
    the instructions said, it should be mixed 1:2:100 (dev:b-sol:water)

    say, if i wanted to use borax (or something else of lower ph) as the b-solution. because it's said that borax gives finer grain. since the ph is lower now, how would i compensate for that? with a longer developing time or with a higher percentage of b-solution in the working solution (like: 1:2:100 or even 1:3:100).
    and would the less active developer effect the light sensitivity of the film too? in other words, would i need a lower asa rating?

    on a related note:
    one thing that always interested me, was, w.eugene smith said in the "darkroom" book, that he uses d-76 with three times (more or less, i can't remember exactly) the normal amount of borax, because this gives him a negative with more shadow detail. is this because of the higher ph-value? and would that effect be even more when one would use carbonate or hydroxide?
     
  11. sanking

    sanking Member

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    There is really no way to compensate for the lower pH of Borax. The threshold pH of pyrocatechin is about 10.5 so the low pH of Borax just doe not work.

    You might, as Pat Gainer has suggested, mix the borax with some sodium hydroxide as this will increase the pH. I don't know exactly how of each is needed but if I were doing this I would just first mix up a borax solution, then add sodium hydroxide until it reached a pH of about 11 - 11.5.

    The working pH of Pyrocat is about 10.9 - 11.2.

    Sandy King