Ammonium Thiosulfate or Sodium Thiosulfate

Discussion in 'B&W: Film, Paper, Chemistry' started by hka, Oct 14, 2007.

  1. hka

    hka Member

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    Is it possible to use Ammonium Thiosulfate instaed of Sodium Thiosulfate as Hypo in Farmer's reducer??
    What about the conversion rate??
    At the moment I have Ammonium Thiosulfate 58-60% liquid on the shelf.
    I do need 120 grams of Sodium Thiosulfate and water to make 500 ml.
    How much Ammonium Thiosulfate (in ml) do I have to add to make also a stock solution of 500 ml?
     
  2. Michel Hardy-Vallée

    Michel Hardy-Vallée Membership Council Council

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    In theory, I would say yes, given that ammonium thiosulfate is a reducer in an acidic solution, much more so than sodium thiosulfate. That's why one should not over-fix with rapid fixer, otherwise you lose densities.

    As for the practical side, er, sorry, no idea! I just read books but I don't apply their knowledge :wink:
     
  3. Ian Grant

    Ian Grant Subscriber

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    Try a 10% solution Harry and test it on some scrap prints. 50g/litre.

    Maybe start with a solution slightly more dilute than when using Sodium Thiosulphate.

    Ian
     
  4. Photo Engineer

    Photo Engineer Subscriber

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    Ammonium thiosulfate mixed with ferricyanide is so powerful, it becomes a rapid, one-shot blix. You could totally remove your image without wanting to. I suggest careful trials.

    PE
     
  5. dancqu

    dancqu Member

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    I'd be careful with that. Potassium ferricyanide itself
    is and oxidizer. It oxidizes elemental silver into silver
    ferrOcyanide. What it will do to ammonia I couldn't
    say. You could do as some others and fix after
    the "bleach". The fix is the "bleach". Dan
     
  6. Photo Engineer

    Photo Engineer Subscriber

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    Dan;

    It is safe to mix ammonia with ferricyanide, but ferricyanide is an oxidant and thiosulfate is a reducer. These mutually react and the solution decomposes. In addition, they both react with silver metal and dissolve it utterly.

    It is a coin toss as to which takes place first. Usually, the silver goes then the rest of the reactants mutually destruct.

    PE
     
  7. georgegrosu

    georgegrosu Member

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    Harry,
    for fixer I use normal a Kodak formulas for ECN 2. (http://www.kodak.com/US/en/motion/support/processing/h24.shtml module 7 - Process ECN-2 Specifications - FORMULAS AND ANALYTICAL SPECIFICATIONS - Fixer). I use this solution for b/w or color films. Is a fast fixer. When you use Sodium Thiosulfate pentahydrate, the concentration is 200 – 250 g/1000 ml of solution for fixer.
    With Ammonium Thiosulfate (solution 58 %) you can use 185 ml/1000 ml fixer.
    Is good if you use sodium sulfite in the fixer because this component stops the reaction:
    Na2S2O3 = Na2SO3 + S (colloidal) for Ammonium Thiosulfate the reaction is similar, but is much complicate for write.
    Normal, I use two fixer: first – used and second fixer – fresh.

    George
     
    Last edited by a moderator: Oct 15, 2007
  8. georgegrosu

    georgegrosu Member

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    Sorry,
    I have same problems with the Kodak link.

    George
     
    Last edited by a moderator: Oct 15, 2007
  9. dpurdy

    dpurdy Member

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    Isn't the regular Kodak rapid fix Ammonium thiosulfate? I have been using that with Potas ferricyanide to bleach prints for a million years. Or at least 20.
     
  10. hka

    hka Member

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    Thanks. I will give it a try.
     
  11. georgegrosu

    georgegrosu Member

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    When I want to bleach (total) prints I use the bleach formula from ECN 2 process (potassium ferricyanide .. 40 g and sodium bromide ….. 25 g all for 1000 ml solution. After a good wash go in the fixer. In this case, you can have a good control of process (solution with constant proprieties) that a singe solution (have a little life of work). If you want only reducer a little of general density of the print I think this option is good if you use a dilution 1:5 for bleach solution.
    For b/w negatives, I use only potassium ferricyanide (1.5 – 2.5 g/ 1000 ml) and after a good washing the film go in the fixer. The speed of silver dissolving, in this case, is little without sodium bromide.
    I thing that the reducer with a single solution have same unknown finish.

    George
     
  12. hka

    hka Member

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    Today I did some experiments with my homebrew Reducer with Ammonium Thiosulfate. As Ian said start with 10% stock solution. With this in mind I made some testprints. Started with a very diluted version with 2,5 ml Solution A and 12,5 ml Solution B at 1 liter water, souping the print for 30 seconds was quite right. This gave me an 0,05 density reducing in the highlights just enough to give it that sparkle I needed.