Sodium Thiosulphate (Hypo) - Lifetime

Discussion in 'B&W: Film, Paper, Chemistry' started by Shangheye, Jun 16, 2008.

  1. Shangheye

    Shangheye Member

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    Does anyone know what the lifetime is of a 10% solution of Hypo? I have done some fixing of a couple of salt prints and then poured the solution back in the bottle (like I do with Rapid fixer) for re-use later. IS that OK...or should I be treating it as one-shot fixer? How can I test its suitability for re-use (eg some form of clearing test like for rapid fixer).

    Rgds

    Kal
     
  2. Tom A

    Tom A Member

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    If it is a pure Hypo-solution (no sodium sulfite), then its lifetime is max 24 hour.
    So use it and throw it away.

    Tom
     
  3. Shangheye

    Shangheye Member

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    It's pure, so thanks for the pointer. Rgds, Kal
     
  4. ntenny

    ntenny Member

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    Does hypo dissolve well in propylene glycol, I wonder? The CRC says it's soluble in ammonia and insoluble in alcohol, but has no position on glycol. If it was amenable to a preservative solution the same way that phenidone is, that'd be convenient. (I assume ammonia wouldn't be a useful solvent for this purpose.)

    -NT
     
  5. dancqu

    dancqu Member

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    I regularly use straight S. Thio. at 1% to 2%
    strength for fixing prints. Strength depends on
    paper; fixer requirements vary. One-shot. Dan
     
  6. Paul Verizzo

    Paul Verizzo Member

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    How long do you fix with that ratio? Twenty grams is about 1/10th of the usual minimum. And then there is the matter of how many prints will it fix.

    Inquiring minds want to know.
     
  7. dancqu

    dancqu Member

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    I fix for 31/2 to 4 minutes. A single fix at such a high
    dilution is all that is needed for greatest LE. The usual
    strength of a sodium thiosulfate anhydrous fixer is
    150 to 160 grams per liter; 15 to 16 percent. So,
    1% for Slavich, 10 grams per liter. Good for 3
    8x10s, each in 1/3 liter. Dan
     
  8. Schlapp

    Schlapp Member

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    Would welcome some thoughts as to why my Vandykes bleach out a bit when fixing in straight Hypo/sodium thiosulfate. I was under the impression that Vandykes should get darker! And yes, they do seem to be fixed :smile: