Sulfuric (milky) Fixer

Discussion in 'B&W: Film, Paper, Chemistry' started by haryanto, Jun 12, 2009.

  1. haryanto

    haryanto Member

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    I always get milky fixer when try to add potasium alum to sodium thiosulfate in F6a Ansel Fixer
    the formula is:
    Sodium thlosulphate (hypo) 240.0 grams
    Sodium sulphite (anhydrous) 15.grams
    Acetic acid 48 ml
    Sodium Metaborate 15 grams
    Potassium alum 15.grams
    Water to make 1000 C.c.
    is that any harm to prints?
    How to get rid the milky

    I know there's opinions about not to use hardener but I still want to use it

    thanks a bunch
     
  2. Photo Engineer

    Photo Engineer Subscriber

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    The formula looks fine. The milkiness is not good though. The suspended particles can cause problems with film images and the surface gloss of prints among other problems such as decreased fixing or hardening power.

    The order you give is good, but how much water do you start with? You should start with about 750 ml at about 100 F, then add the first 2 ingredients. When dissolved, add the acid and then the alum. The metaborate should be added slowly while checking pH. The pH should be at about 4.5, no lower, and no higher than 5.5. It should end at about 3.5 - 4.5.

    Is the acetic acid glacial or 28%? This is important.

    PE
     
  3. haryanto

    haryanto Member

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    water 750 ml at first
    yes Acetic acid 28%

    Thanks PE
     
  4. Photo Engineer

    Photo Engineer Subscriber

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    Make sure that the first 2 ingredients are dissolved before adding acid. The early addition of acid can cause sulfurization of the hypo if the pH falls too fast.

    If the pH is too high, then Aluminum Hydroxide will precipitate.

    Hope things work out for you.

    PE
     
  5. haryanto

    haryanto Member

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    the ingredient always dissolved before adding the next, but I'll try to watch the PH

    thanks PE

    Haryanto
     
  6. dancqu

    dancqu Member

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    Milky, likely sulfur. Sulfur dissolves in a solution
    of sulfite to form thiosulfate. I've not run any tests.
    Adding additional sulfite may be a harmless way of
    clearing the fix.

    The ph of any of the ingredients listed can vary;
    eg, the alum may vary from 3 to 3.5. I'd likely
    make up the 750 ml with all the more alkaline
    ingredients, dilute the acid in most of the
    needed remaining water then slowly
    with stirring mix the two.

    Is that the method you've used? Dan
     
  7. haryanto

    haryanto Member

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    Yes Dan, the PH is the accurate way to find the problem, PH more than 4.5 when add Pot Alum will make it milky, I've found my Glacial Acetic acid seems not 99.5% so when I make it up to 28% it's not 28%
    I cant measure the percentage of my Acetic acid,
    I had to add Acetic Acid till to 200ml to reach my fixer PH 4
     
  8. dancqu

    dancqu Member

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    First a correction. In effect sulfur will dissolve in
    a sulfite solution. Actually the sulfite is oxidized
    by the sulfur into the thiosulfate.

    So which is it to be ph 4 or ph 4.5? How do you
    measure ph?

    If you've an accurate scale and can measure an
    exact amount of the acid the determination of
    the acid's specific gravity will be easy. From
    that the acids strength can be found. Goes
    for dilutions as well. Dan
     
  9. haryanto

    haryanto Member

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    PH 4 is after all ingredients except the P alum dissolved
    I measured PH with PH indicator paper merck, not quite accurate but I notice that in PH 5 I got milky when add the P alum
    do you mean that to dissolves the sulfur I had to add sulfite more? or should I just adjust my acetic acid?

    thanks a lot Dan

    Haryanto
     
  10. dancqu

    dancqu Member

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    Remember, the Alum's ph may be as low as 3. If you are
    at ph 4 then add alum you'll be below ph 4. Adding more
    sulfite may clear that milky fix you've mixed. Test
    a portion. Add and stir in a little at a time. Dan
     
  11. haryanto

    haryanto Member

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    Ok Dan, I'll try
    thanks again

    haryanto
     
    Last edited by a moderator: Jun 14, 2009
  12. mcd

    mcd Member

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    I know that you expressed a desire to use the hardener, but you really don't need it for prints. I used to use half the amount of hardner, and then abandoned it completely. You should try it without it, I think that you will like it.