P-C-Soda and Foma: insight into kinetics

Discussion in 'B&W: Film, Paper, Chemistry' started by eumenius, Jan 18, 2005.

  1. eumenius

    eumenius Member

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    Hello friends,
    my story with P-C-Soda developer continues... while trying to develop another roll of 120 type Foma 100 in a developer mixed from dry ascorbic acid, sodium carbonate stock and phenidone solution, I got heavily underdeveloped negatives, though I developed the film in full accordance with my experimentally obtained times! What the *&^%, thought I. Everyone uses this mix, with no such unstability. My education, however (I was one the enzymologist, working with enzyme kinetics), told me somehow that there could exist a kinetically limited phase of the developer activation - say, ascorbic acid relatively slowly forms some transient-state intermediate that is active photographically. I set up an experiment that way: I mixed my developer and let it stand on the table for 45 minutes in beaker. Then I developed a film with it. Result: a good negative with too much of a density, maybe I should develop it for 8 minutes instead of 10. Also I noticed some streaks from uneven development, even when I put the loaded reel in prefilled tank in an instant. The presoaking of the film is required, perhaps - at least in Fomapan case.

    I will write more about my experiments, so my new information will help people to use Gainer system more effectively on a different films.

    Regards from Moscow,
    Zhenya
     
  2. Jordan

    Jordan Member

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    Zhenya, as a chemist who has studied some enzymology I appreciate your insights :smile: However, I have never seen what you have observed in my experiments with "PC-soda" (I use a PC stock in propylene glycol mixed with sodium carbonate). In my limited experience trying to develop Foma with this developer I found that my negatives were consistently underdeveloped, even when trying what I believed to be very generous developing times. I have had similar experiences with Efke films. My results with Ilford films have been very consistent, though.
     
  3. gainer

    gainer Subscriber

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    I suppose the soda is not suspect? Uneven development might be due to something not being completely dissolved at start of development or a flow pattern due to insufficiently random agitation. The fact that activity increased with standing time, yet streaks appeared, seems to show something like that. You might try putting the developer in a bottle which you can shake like a cocktail shaker before development just to make sure that everything is completely dissolved. Also, don't forget that there is a reaction between the alkali and the ascorbic acid that should be completed before development begins.

    If you were to dissolve the ascorbic acid and phenidone in an organic base like TEA as a stock solution, it might be that some of the problem or all of it might disappear. Jay De Fehr has posted this formula and a lot of discussion about it. You no longer need the soda or any other additive. It's a little like home made HC110 only a heck of a lot different.
     
  4. eumenius

    eumenius Member

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    Thanks, Jordan! :smile: You probably have never observed those effects with your reagent only because the transient activated state of ascorbate-phenidone is probably relative stable in glycol, even though the pH is high. You just dilute it to working concentration, and voila - it's already there, eager to find some silver halide. In water this intermediate required for development is probably very unstable, and takes time to form - 45 min proved okay :smile: So if one mixes everything almost from scratch, the attention should be paid to ripen the mixture before cooking the film :smile:

    I am inclined to get stable and good results with Foma films, so I will not give up and make it working :smile:
     
  5. eumenius

    eumenius Member

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    Yes, those streaks look exactly like flow patterns - but the problem is not related to undissolved compounds, because I use my magnetic stirrer to do the job :smile: It's probably my tank that won't work correctly. I will try to use TEA when I get hold on some, but before it I want to understand how to use soda formula with FOMA films and get even sky :smile:

    Zhenya
     
  6. Maine-iac

    Maine-iac Member

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    Zhenya, I agree with Patrick that it sounds like an agitation problem. Since I use this formula consistently and don't have the problem with streaks or uneven development, I'll just say that my standard procedure is to give fifteen seconds of continuous agitation (inversion of the tank) as soon as I have poured in all the developer. Then I give two inversions followed by a sharp tap on the sink (to dislodge air bubbles) every 30 seconds for the remaining time of development. So far this has worked for me. What kind of tank are you using? Mine is stainless steel with steel reels.

    Larry
     
  7. argentic

    argentic Member

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    With PC in PG + soda I noticed streaking with 120 forte films when I agitated too vigorously. (No, I don't mean the streaks below the holes of 35 mm film but streaks that look like bromide-marks.) I never had this problem with Ilford or Kodak films. The streaks dissappeared when I inversed much more gently. I still cannot explain this, but it worked.