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Thread: Obsidian Aqua, catechol staining developer

  1. #221

    Join Date
    Mar 2012
    Location
    France
    Posts
    11

    Re: Obsidian Aqua, catechol staining developer

    Hello
    In a jobo the problem will be oxidation... You will probably have to use higher concentration, slow rotation rate, shorter dev time and more sulfite... Or the base + fog may be too high.
    To my mind, there are better alternatives for jobo. But just try !

  2. #222
    Jon Wilson's Avatar
    Join Date
    Jan 2004
    Location
    Idaho
    Posts
    628

    Re: Obsidian Aqua, catechol staining developer

    Quote Originally Posted by mikoyan View Post
    Hello
    In a jobo the problem will be oxidation... You will probably have to use higher concentration, slow rotation rate, shorter dev time and more sulfite... Or the base + fog may be too high.
    To my mind, there are better alternatives for jobo. But just try !
    Good point. In an effort to process more film while working on my learning curve, I have brought AO home with 35mm & 120mm tanks. Plan to develop some bulk ISO 400 film. Will start between 5-7 min and see what I get.

  3. #223

    Join Date
    Sep 2014
    Posts
    6

    Re: Obsidian Aqua, catechol staining developer

    Ferric ammonium EDTA

  4. #224

    Re: Obsidian Aqua, catechol staining developer

    Just mixed up a batch of OA, for solution B the formula specifies 200g sodium carbonate (anhy) I have washing soda crystals. According to the darkroom cookbook in the conversions section if the formula specifies sod. carbonate (anhy) And you have sod. carbonate crystal you should multiply the specified amount by 2.7. This gave me 200g sod carbonate (anhy) x 2.7 = 540g of sod carbonate (crystal). So I gradually mixed 540g of the crysttal in room temperature water, it has taken an eternity to get the sod. carbonate into solution. I have been stirring for ages, I then transferred the solution into 2 one liter bottles and did a gentle "Indian Club" workout. My shoulders have loosened up great but my B solution still looks cloudy :-( Is the 462g ever going to fully go into a clear solution or have I got the amount wrong? What should the ph of bath B be? With a simple litmus paper test mine is reading ph11 or more (my papers only read to ph11).
    Last edited by GoodOldNorm; 9-Oct-2017 at 06:21. Reason: spelling correction

  5. #225

    Re: Obsidian Aqua, catechol staining developer

    Quote Originally Posted by GoodOldNorm View Post
    Just mixed up a batch of OA, for solution B the formula specifies 200g sodium carbonate (anhy) I have washing soda crystals. According to the darkroom cookbook in the conversions section if the formula specifies sod. carbonate (anhy) And you have sod. carbonate crystal you should multiply the specified amount by 2.7. This gave me 200g sod carbonate (anhy) x 2.7 = 540g of sod carbonate (crystal). So I gradually mixed 540g of the crysttal in room temperature water, it has taken an eternity to get the sod. carbonate into solution. I have been stirring for ages, I then transferred the solution into 2 one liter bottles and did a gentle "Indian Club" workout. My shoulders have loosened up great but my B solution still looks cloudy :-( Is the 462g ever going to fully go into a clear solution or have I got the amount wrong? What should the ph of bath B be? With a simple litmus paper test mine is reading ph11 or more (my papers only read to ph11).
    Problem solved I had mixed the sod. carbonate with my lime scale contaminated tap water, this caused the milky precipitate. I have now mixed part (b) with laboratory grade sodium carbonate (anhy) with deionised water; it took less than 5 mins of stirring. At least I had a good work out and I did learn not to mix the stock solutions formulas with my hard tap water.

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