Question for chemistry wizards....

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

  1. jimgalli

    jimgalli Subscriber

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    I'm out of TF-4 and Kodak Rapid......but I have about 5 pounds of crystaline sodium thiosulfate. I've been mixing about 100g with 600ml of H2O and using it as a one shot then eliminating. Am I compromising my film. Just hypo and water.
     
  2. ann

    ann Subscriber

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    no, however , i believe an acid stop bath is recommended with plain hypo.

    I don't rmember the exact measurements, but am sure ole or someone else will pop up with more specifics.
     
  3. Tom Hoskinson

    Tom Hoskinson Member

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    Jim, for fixing films (and paper), take a look at Ole's Fixer Recipe. I use a water rinse with this fixer - no stop bath.

    http://www.apug.org/forums/article.php?a=38

    This gives you a good fixer that uses your sodium thiosufate plus some ammonium ion for fixing efficiency. You can use it as a one-shot.

    You can also substitute 50 grams of ammonium sulfate for the 40 grams of ammonium chloride (if you don't have the ammonium chloride). If you don't have either chemical, Artcraft will fix you up (bad pun).

    If you are fixing Azo paper, sodium thiosulfate and water works fine. I use an acetic acid stop bath with it.
     
  4. Nick Zentena

    Nick Zentena Member

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    At 100 grams to 600ml the only down side is the amount of hypo you're using. You've got plenty.

    TF-2 is only 250grams to 1litre of water. But it's not one shot.

    I think Adam's plain hypo was about 250 grams to the litre to.
     
  5. srs5694

    srs5694 Member

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    I just took a look at that, but I'd like clarification/confirmation: The formula specifies 20cl of sodium metaborate 10% solution. Is that correct -- cl (centiliters), rather than ml (mililiters)?
     
  6. Tom Hoskinson

    Tom Hoskinson Member

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    It's Ole's recipe - I'll PM him and ask him to verify it.

    A centiliter is defined as a unit of volume equal to one hundredth of a liter or ten milliliters.
     
  7. dancqu

    dancqu Member

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    [QUOTES=Nick Zentena]
    "At 100 grams to 600ml the only down side is the
    amount of hypo you're using. You've got plenty."

    That's true, "plenty". I've many times used 22.5 grams
    penta for Pan F+. That 22.5 grams will clear an entirely
    unexposed roll.

    If testing for a minimum is not to be done then I suggest
    30 grams for slower speed films and 40 should do for any
    others. Any T or D film may need the higher amount.

    For one-shot use there is no point in adding preservatives
    or ph modifiers. The ph of sodium thiosulfate runs just
    shy of 7. S. Thio. is a very handy, quick fix to mix;
    fresh fix each use. Allow time for it to warm. Dan
     
  8. jimgalli

    jimgalli Subscriber

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    Thanks everyone.
     
  9. Ole

    Ole Moderator Staff Member Moderator

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    Yes, that's correct. But it is also fairly uncritical - anything between 5 and 30 cl gives about the same result. I found out that I used about 20cl, so that's what I wrote down. Sometmes I drop it altogether, for pH closer to neutral. I like having it in when using pyrocatechin developers as metaborate seems to have an added "stop-effect" on pyrocat.