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  1. #1
    McFortner's Avatar
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    Sodium Thiosulfate fixer

    I found a formula for using Sodium Thiosulfate as a fixer:

    2000ml distilled water
    100g sodium thiosulfate

    Pour the distilled water into a pot and heat it on a hot plate to 125°F. Transfer it to a large graduate. Gently sprinkle the sodium thiosulfate into the water. Stir with a mixing rod until all the crystals have dissolved. Pour the solution into a dark brown glass or plastic bottle. Lable this bottle "Sodium Thiosulfate/VDB fixer". This fixer will last for a year or so.
    It's from Photo-Imaging: A Complete Visual Guide to Alternative Techniques and Processes (the book is on it's way from Amazon.com as we speak). What I was wondering is if I have to dilute this to use with 35mm film negatives, or can I use it straight. Also, how long do I use it to properly fix the negatives? I'll be using caffenol as a developer and the sodium thiosulfate should be arriving tomorrow in the mail, so any help would be greatly appreciated. I'm basically trying to keep costs down so I can afford to develop b/w at home plus experiment some once I get better at it!

    Thanks,
    Michael

  2. #2
    Anscojohn's Avatar
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    Seems weak to me, a non-chemist. Usually a ca. 20-24% solution is about right. And I doubt you need distilled water.
    John, Mount Vernon, Virginia USA

  3. #3
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    That formula look like weak plain hypo. I suspect this may last a session of fixing but not any more than that. Plain Hypo calls fro 480G S.Thio. If you add sodium bisulfite 45g to Plain Hypo you get Acid Hypo and will keep and can be reused. Better economy then the formula you posted.

    To determine how long to fix, snip a bit of the film leader and place in the hypo and time how long it takes to clear. Double that and that is how long you should fix, or longer.

    HAve fun developing and good luck
    D-76 is a standard developer, although not one I use.
    Ansel Adams - The Negative

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    The suggested labeling of "Sodium Thiosulfate/VDB fixer" suggests that this is not intended for film or paper, but instead for Van Dyke Brown (VDB). That would be consistent with the title of the book that you mention.

    A better approach for film and paper formulas would be Anchell's Darkroom Cookbook. Also, there have been any number of posts and articles here and elsewhere with formulas for hardening, non-hardening, odorless, and one-shot fixers---a little Google searching should pay off quickly.

    As an aside, fixer is not likely to be one of your major expenses, and is one of the less rewarding things to experiment with. If you want a good, low-cost, long-lived fixer, TF4 from Photographer's Formulary should fill the bill, or one of the generic fixers from Freestyle.

    Good luck!

  5. #5

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    VDB images are fragile. Concentrated fixers destroy them. But they are similar to conventional silver images in that you need to remove the non-image-forming silver salts. In order to preserve the image, VDB uses about a five percent hypo solution to fix and darken the tone. Conventional silver film needs a more concentrated solution to remove the non-image silver salts. Traditionally, a 24 percent hypo solution (plus preservatives, pH adjusting ingredients, and possibly wash agents and hardeners) as a fixer. Faster fixers are based on 8 to 12 percent ammonium thiosulfate solutions.

  6. #6

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    Others have posted good information. Here are a few links to fixer formulas:



    Some of these links include further information on fixers generally, so you can learn a good deal by checking out these links, even if you don't plan to make those specific fixers.

    A plain fixer, such as the one you posted, Michael, won't last long in solution -- or so I've read. I'm therefore skeptical of the 1-year shelf-life claim. Or maybe I'm just disremembering. Most fixers include additional ingredients to extend their lives in solution, change their pH, add hardeners, or whatever.

    The first three links I've presented are to fixers based on sodium thiosulfate, and the last three are to fixers based on ammonium thiosulfate. Sodium thiosulfate fixers generally work more slowly than ammonium thiosulfate fixers and they're usually more expensive, in my experience. For instance, according to my calculations, TF-2 costs $0.09/roll, whereas TF-3 costs $0.03/roll. A sodium thiosulfate fixer might be more cost-competitive if you can find a cheap local source for the stuff, though. My cost estimates are based on shipping it (and ammonium thiosulfate, for that matter). Mixing your own won't really save much, either. Kodak Flexicolor fixer, which is a rapid fixer intended for C-41 film but that works fine with B&W film, costs about $0.05/roll. TF-4 costs $0.12/roll, if my calculations are correct -- a little pricey by rapid fixer standards, but it works very quickly.

    So overall, I'd say you might want to reconsider and just buy Flexicolor Fixer or some other rapid fixer. Of course, if you've already got a load of sodium thiosulfate on the way, you might as well use it. Mix it up in small quantities as plain fixer or add the other ingredients to help preserve it and you should be able to fix plenty of film and/or paper with it.

  7. #7

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    Quote Originally Posted by McFortner View Post
    What I was wondering is if I have to dilute this to use with
    35mm film negatives, ... Also, how long do I use it to properly
    fix the negatives? ... the sodium thiosulfate should be arriving
    tomorrow in the mail, so any help would be greatly
    appreciated. Thanks, Michael
    Not to worry. Which sodium thiosulfate have you coming?
    The penta hydrate has water attached while the anhydrous
    is H2O free.

    Assuming the penta, your fixer according to the formula
    given is already dilute. Actually I use a film fixer of
    EXACTLY the same formula. The fixer is used one-
    shot, one 120 roll, 500ml, then down the drain.

    If you've a scale good for 1 ounce and have the penta
    thiosulfate coming, add that amount to the solution volume
    needed for fixing 1 35mm roll. Allow 10 minutes with some
    off and on agitation then check for clear. That's a starting
    point, not all details; the anhydrous, paper, etc. Dan

  8. #8
    McFortner's Avatar
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    Quote Originally Posted by dancqu View Post
    Not to worry. Which sodium thiosulfate have you coming?
    The penta hydrate has water attached while the anhydrous
    is H2O free.
    Yes, I have the penta coming. So I can use it straight for a one time use then, or add more chemicals for more versatility and usefulness. That's interesting. I guess I have a lot of choices here to pick from!

    Michael

  9. #9
    BetterSense's Avatar
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    If my envelope is correct, one should use about 30% less if one has the anhydrous version. Anyone back that up with experience?

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    Sodium Thiosulfate Conversion

    Better Sense,

    Here are the conversion factors for Sodium Thiosulfate:

    Note that the crystalline (pentahydrate) form is heavier, i.e., you need more of it to equal the same amount of chemical contained in the anyhdrous version (water adds weight but does not increase the actual amount of chemical):


    You want to use crystalline instead of anhydrous (i.e., the formula calls for anhydrous but you have only the crystalline): multiply the amount required by 1.57.

    You want to use anhydrous in place of crystalline (the formula calls for crystalline, but you have anhydrous): multiply by 0.64.

    Hope this helps,

    Doremus Scudder
    www.DoremusScudder.com

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