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Thread: Obsidian Aqua, catechol staining developer

  1. #31

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    Re: Obsidian Aqua, catechol staining developer

    Hi Dan,

    I'm experimenting with the geometric agitation scheme, but I'm not sure I can recommend it as having any practical advantage over more typical schemes. I'm not sure whether you mean FP4+, or HP5+.

    For FP4+, try OA 1:500, 9:00, 70F, with a geo sequence of 30 seconds initial agitation followed by 10 seconds at 2:00, 4:00, 8:00, or a more standard sequence of 2:00, 4:00, 6:00.

    For HP5+, try OA 1:500, 15:00, 70F, with a geo sequence of 30 seconds initial agitation followed by 10 seconds at 3:00, 6:00, 12:00, or a more standard sequence of 3:00, 6:00, 9:00, 12:00.

    These are WAGs based on my experience with other films, and not on testing these films, so don't commit important films to these recommendations. Optimum development produces a negative with a density range suitable for the printing process, so one must know the exposure scale of the printing process, and the brightness range of the scene to determine best exposure and appropriate development. My WAGs should give you a printable image upon which to base further adjustments to exposure, development, and agitation. Be aware these low frequency agitation schemes will produce pronounced edge effects that might not be suitable for all images.

    If you're wary of making up a liter of OA (quite a commitment), you can make 100ml:

    Distilled water 70ml
    Metabisulfite (sodium or potassium) 2g
    Catechol 25g
    Distilled water to 100ml


    This will make 50 liters of 1:500 working solution, which should be enough to give you a good feel for its characteristics and working properties.

    Good luck, and feel free to contact me with any questions or comments, here, or directly at:

    jdefehr@gmail.com

  2. #32

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    Re: Obsidian Aqua, catechol staining developer

    Jay: thank you for suffering a fool; I meant to write FP4+.

    I appreciate the starting development times; and I do plan to just expose a few sheets on something mundane near my home for testing, I also was thinking of making up a small batch to play with.

  3. #33
    IanG's Avatar
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    Re: Obsidian Aqua, catechol staining developer

    Is this not just a very minor variation on pre-WWII Pyrocatechin developers ?

    Ian

  4. #34

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    Re: Obsidian Aqua, catechol staining developer

    Dan,

    If that makes you a fool, I'm a founding member of that club! Good luck!

    Ian,

    There are many, many developers based on catechol; some use carbonates while others use hydroxides, some are staining developers, some are not, some are 2-bath developers, and all are variations on the same theme; that theme being catechol as the sole developing agent. Catechol staining developers that include a secondary, or multiple developing agents is a new theme of dubious value.

    Whether my variation is major or minor (or very minor) depends on your criteria. Differences among developers that share common ingredients might appear to be minor, but the effects of varying proportions and concentrations can be dramatic. Catechol + hydroxide + KBr can be used to make a very effective lith print developer, or an equally effective compensating film developer by just such variations.

    Pre-WWII films were much different than the films we use today, especially the newest technology films, like TMY-2 and Acros, etc. One might be able to take a pre-WWII catechol/carbonate film developer and adjust dilution alone to give acceptable results with modern films, but that seems a pointless limitation. These kinds of developers are so simple, it just makes more sense (to me) to start with a set of design goals and try to achieve them in the most direct way possible. This is what I've done with Obsidian Aqua, and it should come as no surprise to anyone that OA bears a family resemblance to other developers of its kind.

    Some differences:

    OA is the most concentrated developer of its kind. This strategy achieves two design objectives: improved keeping properties, and improved image stain. Increasing the concentration of the stock allowed me to increase the ratio of developing agent to preservative in the working solution for improved staining, while simultaneously decreasing the ratio of preservative to total solution volume in the stock, for improved keeping.

    OA uses a lower concentration of carbonate than other developers of its kind. Modern films don't require the high carbonate developers pre-WWII films did, so OA works at a pH 10X or more, lower than pre-WWII developers, and requires no restrainer.

    OA working solution is more dilute than other developers of its kind. Pre-WWII developers typically used 2 or more grams of catechol per liter of working solution, while OA uses 0.5g per liter. A more dilute solution is more prone to local exhaustion during development, and the edge and compensating effects that result from local exhaustion. This in turn increases the appearance of sharpness in the negative and the print.

    Taken together, the above combine to form a very different developer. One couldn't make a pre-WWII developer perform like OA without adjusting it to become OA.

  5. #35
    Lachlan 717
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    Re: Obsidian Aqua, catechol staining developer

    Quote Originally Posted by Jay DeFehr View Post
    OA uses a lower concentration of carbonate than other developers of its kind. Modern films don't require the high carbonate developers pre-WWII films did, so OA works at a pH 10X or more, lower than pre-WWII developers, and requires no restrainer.
    Thanks for this thread, Jay.

    How do you think OA will go with the more traditional/old style films, such as Adox/Efke?
    Lachlan.

    You miss 100% of the shots you never take. -- Wayne Gretzky

  6. #36

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    Re: Obsidian Aqua, catechol staining developer

    Hi Lachlan,

    Even our "old style" films are very modern compared to pre-WWII stuff, and OA will work very well with them. Ilford PF+ is a fairly "old-style" film, and one of my favorites with OA. Foma films look great, too. I'll try some of the Efke/Adox stuff when I get home, but I'm very confident it will look great. These films benefit from a tanning/hardening developer like OA, and can be extremely sharp. OA is cheap-- give it a go!

  7. #37
    Lachlan 717
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    Re: Obsidian Aqua, catechol staining developer

    Quote Originally Posted by Jay DeFehr View Post
    Hi Lachlan,

    Even our "old style" films are very modern compared to pre-WWII stuff, and OA will work very well with them. Ilford PF+ is a fairly "old-style" film, and one of my favorites with OA. Foma films look great, too. I'll try some of the Efke/Adox stuff when I get home, but I'm very confident it will look great. These films benefit from a tanning/hardening developer like OA, and can be extremely sharp. OA is cheap-- give it a go!
    Thank again, Jay.

    This seems to be a set of chemicals easily (although not initially cheaply) available in Australia (the Catechol if $65 for 100g!!). However, with the dilutions you recommend, this will amotise into a very cheap brew quite quickly.

    So much easier to do this that wait for PF to send through some of their Pyro kits...
    Lachlan.

    You miss 100% of the shots you never take. -- Wayne Gretzky

  8. #38

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    Re: Obsidian Aqua, catechol staining developer

    Quote Originally Posted by Lachlan 717 View Post
    Thank again, Jay.

    This seems to be a set of chemicals easily (although not initially cheaply) available in Australia (the Catechol if $65 for 100g!!). However, with the dilutions you recommend, this will amotise into a very cheap brew quite quickly.

    So much easier to do this that wait for PF to send through some of their Pyro kits...
    Lachlan,

    I had no idea catechol is so expensive in Australia. It seems it would be cheaper to order it in from Artcraft at US$26.00/ 250g + shipping. This is a major motivation for this formula. Metabisulfite, carbonate and water are available almost everywhere, and a little catechol goes a long way, so shipping catechol alone shouldn't be prohibitive. I hope you can find a better deal on your catechol. Good luck, and let me know if I can be of any help.

  9. #39
    Cor's Avatar
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    Re: Obsidian Aqua, catechol staining developer

    Jay,

    Could you give a starting point for Ilford PanF, expose box speed I guess, but process for how long at what temperature?

    Thanks,

    Cor

  10. #40

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    Re: Obsidian Aqua, catechol staining developer

    Very interesting...
    Thanks for sharing Jay

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