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  1. #1

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    A very low contrast, low pH, full speed POTA variant

    I thought this would be fun to post based on continuing experiments with low contrast developers. This was only a first attempt in this particular direction so I'm wondering how far it can go with modifications, substitutions etc. It is essentially a modification of Horwitz's D-512 which was based on research by Levy into the superadditivity of Phenidone and Pyrogallol.

    It is only preliminary and should be considered a "first cut", but perhaps worth playing with. The formula is:

    20g sodium sulfite
    1g Pyrogallol
    1g Dimezone-S
    --------------
    1L

    A H&D curve for 35mm TMX is attached. Development time was 10:00 at 68F, without any fancy routines. Basic inversion agitation for 30 seconds initially, followed by 10 seconds each minute. There appeared to be some orange-ish imagewise stain at high exposure densities so I measured using white light, blue and green. Preliminary observations:

    -Marked toe contrast and full film speed (equivalent to normal development in XTOL)
    -Equivalent contrast of ~N-3 or more in ZS terms
    -Uniform development
    -Normal fog level (same as XTOL)
    Attached Thumbnails Attached Thumbnails TMX.jpg  
    Last edited by Michael R 1974; 01-20-2014 at 09:26 AM. Click to view previous post history. Reason: tyop

  2. #2
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    Interesting work, Michael. Thanks for sharing this.

  3. #3
    MDR
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    Thank you

  4. #4
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    Very interesting variation, but I wonder why it has to use Pyrogallol as secondary developer, and not one of the less toxic options. The composition of this developer also suggests that one must mix it from scratch every time one wants to use it, there is no convenient concentrate like Pyrocat.
    Trying to be the best of whatever I am, even if what I am is no good.

  5. #5

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    Agree it is a one-shot scratch mix but I'd call it a "special purpose" developer rather than a general purpose developer like Pyrocat etc.

    Also agree it would be worth trying other variations with a more friendly substance than Pyro. Perhaps an amount of HQ or even sodium ascorbate. Substitutions/alterations would have to be determined empirically, and image structure characteristics need to be evaluated, but what I find particularly interesting is the high emulsion speed and extreme low contrast this preliminary formula gives at a relatively low working pH.

    In Anchell/Troop some similar things were suggested as ways of "stabilizing' the original POTA formula, but the suggestions were primarily aimed at document films and contain relatively small amounts of the secondary/regenerating agent.

    Lots of things one could experiment with here. Less sulfite, maybe add a small amount of alkali, further dilution, etc.

    Since I don't have a pH meter, any idea approximately what the pH of this working solution would be?
    Last edited by Michael R 1974; 01-20-2014 at 02:15 PM. Click to view previous post history.

  6. #6
    Rudeofus's Avatar
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    Quote Originally Posted by Michael R 1974 View Post
    Also agree it would be worth trying other variations with a more friendly substance than Pyro. Perhaps an amount of HQ or even sodium ascorbate.
    The great thing about Ascorbate would be that Pat Gainer already did most of the work for us and provided us with a nice curve plot what we should expect from low amounts of Ascorbic Acid. Conclusion: we will most likely get a straight curve, and an emulsion speed comparable to regular PC developers, i.e. full speed.

    Quote Originally Posted by Michael R 1974 View Post
    In Anchell/Troop some similar things were suggested as ways of "stabilizing' the original POTA formula, but the suggestions were primarily aimed at document films and contain relatively small amounts of the secondary/regenerating agent.
    My reading of TFDC is that they recommended highly diluting common developers while keeping them quite alkaline. I tried that once (in a very unprofessional test) with Delta 3200, and the results were unsatisfactory. Delta 3200 in POTA and Delagi 8, on the other side, can give you very nice results.

    Quote Originally Posted by Michael R 1974 View Post
    Since I don't have a pH meter, any idea approximately what the pH of this working solution would be?
    I did measure pH of POTA some time back: 8.42. POTA contains more Sodium Sulfite and no Pyrogallol, but I would suggest that your soup was somewhere in that pH range.

    Reformulate it to use a different second dev, and I'll measure pH for you
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  7. #7

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    With moderate to large amounts of sulfite the action of pyrogallol is very similar to that of Metol. In addition it is super-additive with phenidones.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  8. #8
    Rudeofus's Avatar
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    Quote Originally Posted by Gerald C Koch View Post
    With moderate to large amounts of sulfite the action of pyrogallol is very similar to that of Metol.
    Is 20-30 g/l a "moderate to large amount" ?
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  9. #9

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    Good question.

    But if Pyrogallol in the presense of moderate/large amounts of sulfite functions similarly to Metol, does that mean it is no longer superadditive with Phenidones when there is a lot of sulfite? (because Metol is not superadditive with Phenidones as far as I know).

    A lower amount of sulfite (say 5-10g/L) might be something to try here. My first experiment will be to replace the Pyro with HQ and see what happens from a sensitometric perspective. The idea is to retain both high emulsion speed and extreme low contrast.

    To respond to Rudeofus's earlier comment regarding FDC recommendations, I have to say in general I have not found the "dilute for higher speed" maxim to work very well with general purpose developers. "Dilute and increase alkalinity for higher speed" seems to work sometimes (depending on the film), but not very well either. That's why in my quest for high speed/low gamma development (without golfball grain) I decided to go in the opposite direction recommended in FDC. Research by Levy and Shepp/Kammerer seems to point in this opposite direction. Who knows - maybe we can even find a tanning/staining Pyro formulation which works at a low pH.

  10. #10
    Shawn Dougherty's Avatar
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    Quote Originally Posted by Michael R 1974 View Post
    A lower amount of sulfite (say 5-10g/L) might be something to try here. My first experiment will be to replace the Pyro with HQ and see what happens from a sensitometric perspective. The idea is to retain both high emulsion speed and extreme low contrast.
    I would be very interested in a (non-staining) developer, like what you mention above, which gives decent film speed and is mixed up as needed for extremely high contrast scenes... especially a developer that allowed use of "normal" agitation procedures or more specifically rolling in tubes. I'm following this with interest.

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