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  1. #11

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    Quote Originally Posted by jdef
    Tom,

    I know that catechol developers work in carbonate solutions (Pyrocat HD), or TEA solutions (Cat-P-TEA) given enough time or concentration, but in my testing I get more activity from less concentration using sodium hydroxide as the alkali, which to me, is better. A dilute solution of Sodium hydroxide is stable enough to do its job in a one-shot working solution, so in this application its stability is not a factor. Incidentally, the biggest surprise I've found in this developer is the extremely fine grain. The conventional wisdom that high acutance, sulfite-free developers sacrifice grain for sharpness, but that doesn't hold true with this developer. I can't find grain to focus on with HP5+.

    Jay
    The hydroxides have been widely used with pyrocatechin based developers and it should come as no surprise that they give greater activity with pyrocatechin than the carbonates. In the Pyrocat-HD formula, to get to the same pH, and energy, you must substitute carbonate for hydroxide at about a 10:1 ratio. You could also substitute tribasic sodium phosphate at about the same ratio, or slightly less. However, there is a lot more to a good developer than its level of activity or energy.

    When I developed the Pyrocat-HD formula I experimented with numerous activators, including the hydroxides, the carbonates, and TSP. Based on several criteria I concluded that the carbonates, in spite of the fact that they are not as efficient as the hydroxides, are a better and more rational choice for this developer. With carbonate the stock solutions are more stable, the working solutions are better buffered, and there is less chance of pin holes on the negatives, especially when using acid stop baths. Also, the grain is definitely finer in the Pyrocat-HD formula with carbonate.

    So, while there is no doubt in my mind but that the hydroxides work very well with pyrocatechin based formulas such as Pyrocat-HD, and they are definitely more efficient in some respects, I simply don't think they are the best choice.

    Sandy

  2. #12

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    Quote Originally Posted by Mehmet Kismet
    For more contrasty highlights, that I prefer in my works, the brown color stain of the hidroquinon is better then the green-yellow stain of pyrogallol.
    Mehmet - "better" is a personal choice here - as the yellow stain of the pyrogallol may be better for someone elses contrasty subjects...

    Thanks for the formula, I'll give it a try.

    Kirk - www.keyesphoto.com

  3. #13

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    Quote Originally Posted by Kirk Keyes
    Mehmet - "better" is a personal choice here - as the yellow stain of the pyrogallol may be better for someone elses contrasty subjects...

    Thanks for the formula, I'll give it a try.

    Kirk - www.keyesphoto.com
    Hi Kirk,

    You are absolutely right. That is only my preference. When I precised that I prefer that developer for the contrasty highlights in my work, I ment the contrasty highlights on my prints, not on the subjects.
    I agree with you that the pyro color flattens somehow the highlights on the multigrade papers, so if the subject itself is contrasty, the pyro could be a better choice.

    Best
    Mehmet Kismet

  4. #14

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    Quote Originally Posted by Mehmet Kismet
    Hi Kirk,

    You are absolutely right. That is only my preference. When I precised that I prefer that developer for the contrasty highlights in my work, I ment the contrasty highlights on my prints, not on the subjects.
    I agree with you that the pyro color flattens somehow the highlights on the multigrade papers, so if the subject itself is contrasty, the pyro could be a better choice.

    Best
    Mehmet Kismet
    Quite right! I maintain separate stock solutions of Pyrogallol, Pyrocatechol, Hydroquinone and Phenidone dissolved in Propylene Glycol which allows me to "tune" the developer if the situation requires it.
    Tom Hoskinson
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    Everything is analog - even digital :D

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