Fixer and hardener in reversal process

Discussion in 'B&W: Film, Paper, Chemistry' started by Alessandro Serrao, May 2, 2009.

  1. Alessandro Serrao

    Alessandro Serrao Member

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    I was preparing from scratch the kodak f5 fixer omitting the acetic acid and the potassium alum since I have them both in the Tetenal hardener:

    sodium hypo 240g
    sodium sulfite 15g
    boric acid 7,5g
    water to make 1lt

    then I allowed the solution to warm up and added the tetenal hardener (potassium alum and acetic acid).
    Immediately a sludge of alluminium sulfate formed.
    How come?
    Is the f5 fixer built to avoid just this?

    Second question: If I use the tetenal hardener as a stop bath, will I loose the mordanting effect of potassium alum due to the following bleach bath?
     
  2. thmm

    thmm Member

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    If it is a white sludge, it is probably sulfur! The thiosulfate (hypo) ion reacts in sufficiently acidic environment to produce sulfur, which forms small particles and makes the solution appear milky, and sulfur dioxide. The acidity of alum in solution is in fact enough to make this happen.

    Therefore, a fixer that is to include hardener needs to be buffered sufficiently to prevent the pH from dropping too low, which is achieved by the combination of sodium sulfite and boric acid here. This means that there are two ways to prevent the fixer from degrading: either add a smaller amount of the hardener, or increase the amount of sodium sulfite and boric acid while keeping the proportion of 2:1 between the two chemicals. Since you mix your own, a bit of experimentation may be in order to find a working recipe.
     
  3. Photo Engineer

    Photo Engineer Subscriber

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    F5 is a hardening fixer. and is built for just such addition, but you must be careful about acid addition or it will sulfurize if the acid is too concentrated, or the aluminum will precipitate as a hydroxide if the acidification is too slow. So, there are two ways this can go depending on acid concentration or pH.

    Why not use the "real" F5 formula with acetic acid and alum? It is correct and does the job with no need for questions.

    PE
     
  4. Alessandro Serrao

    Alessandro Serrao Member

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    Because I have still a bottle almost full of Tetenal hardener and don't have potassium alum.

    I'll try the hardener as a stop bath instead.
     
  5. Photo Engineer

    Photo Engineer Subscriber

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    It will probably be too acidic, IDK for sure. Sounds like the Tetenal hardener is more concentrated than the Kodak variety. IDK. Best of luck.

    PE
     
  6. filmanswerman

    filmanswerman Member

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    Caution: Remember to wear an excellent filter mask when mixing dry chemicals.

    You are totally correct in your post. Hardener is easy to screw up if one does not add it correctly and in a diluted method with slow additions.

    Aside from this, I have been trying to educate everyone that mixes developer or fixer to be aware of the need to utilize proper precautions.

    1. Wear a proper mask! Not the dime store variety but something akin to what you would utilize if you were painting a car or spraying poison. Hydroquinone is known to metabolize in the liver and this generally causes mutations and DNA damage. It is for that specific reason why it is suggested that hydroquinone is responsible for a wide variety of cancers in humans. Hydroquinone has been linked to certain cancers of the blood such as leukemia and also damage of the kidney. Studies have shown that when used, hydroquinone is absorbed and the released out of the kidneys very slowly.
    2. Studies and debates continue about just how dangerous ‘inhaling’ dry compound hydroquinone is. We know it causes cancer in animal tests.
    3. Defenders point out that while it causes cancer in animals it has never been demonstrated to perform identically in humans. {My opinion is that humans are animals. The inhaling of hydroquinone powder was cited as a benchmark in several key tobacco lawsuits.}
    4. So be safe a protect yourself:
    a. Wear a mask and a good one.
    b. Wear gloves.
    c. If you spill hydroquinone, or potassium sulfite {a proven asthma inducer} have the area cleaned professionally.
    d. Never wear the same clothes home to your family.
    e. Wear proper gloves, apron, eye protectors, mask, and shoe covers.
    5. If you can’t comply with safe utilization of mixing powders, then utilize pre-made liquids that are assumed infinitely safer! Just how much money are you saving if you don’t have the proper safety equipment?
    6. This was not intended as a complete list. A emergency eye bath and a shower in very close proximity is also a very good idea!
    7. Full disclosure: Can you tell I am not a big fan of chemical powder mixing for underprepared casual photography buffs? I have mixed powders for years and I have a very healthy respect for caution and pre-cautions. This is not a cake mix!
     
  7. Alessandro Serrao

    Alessandro Serrao Member

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    Tomorrow I will mix some dichromate for the first time.
    Guess what...