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  1. #11

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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.

  2. #12

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    Quote Originally Posted by john_s
    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.

    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

  3. #13

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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?
    "Fundamentally I think we need to rediscover a non-ironic world"
    Robert Adams

  4. #14

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    Quote Originally Posted by Jim Chinn
    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?
    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

  5. #15
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    Quote Originally Posted by sanking
    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.
    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

  6. #16

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    Quote Originally Posted by john_s
    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.
    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.
    Tom Hoskinson
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  7. #17
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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.
    Gadget Gainer

  8. #18
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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.
    Gadget Gainer

  9. #19

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    Thanks for the response Sandy.
    "Fundamentally I think we need to rediscover a non-ironic world"
    Robert Adams

  10. #20
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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

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