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  1. #21

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    Quote Originally Posted by Rafal Lukawiecki View Post
    Thank you, Gerald. May I ask you to clarify, therefore, if this also means that, in your opinion, sodium sulfite does not fulfil any roles in desorbing the silver-thiosulfate complexes from the emulsion, especially those adsorbed to the silver crystal grains (as opposed to just the paper fibres), nor can it aid in converting the less soluble complexes to the more soluble ones, as Doremus stated earlier? I appreciate your opinion on this, very much.
    In the pasted article from Ryuji Suzuki's web site a few posts above, he does say "Sulfite is superior in that sulfite can desorb not only unreacted thiosulfate but also sparingly soluble and adsorbed argentomonothiosulfate complex."

    I understand that the complexes are less soluble than thiosulphate and are thus harder to wash out. So if Suzuki is right, the sulphite does in fact help to wash out the complex (at least the mono one), if not "convert" it. I don't know where Suzuki got that information. Maybe it's in one of the research papers from Kodak in the golden age of black and white.

    The other thing that I find interesting is that once the sulphite bath is used, washing can proceed in colder water than would be needed for timely washing without the sulphite bath. This has a practical application for many people whose tap water is rather cool and who don't have a mixer.

  2. #22

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    Whether the silver complexes are adsorbed in the emulsion or trapped in the the paper fibers is really immaterial in a practical sense. What is important is the kinetics of the process. The silver complexes in film and RC papers are removed much more quickly with washing than those in FB papers. So what controls the rate of silver removal in FB papers is absorption on the paper base. In any set of kinetic reactions it is the slowest reaction which determines the overall speed.
    Last edited by Gerald C Koch; 03-21-2013 at 09:55 AM. Click to view previous post history.
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  3. #23
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    Here is a question for you gurus.

    Last year I was having problem with my clearing agent and water, I was getting scum (white deposits) on final prints even after proper wash.

    It was suggested here ( thank you) to add Sodium Hexametaphosphate to my Sodium Sulfite.

    the scum problem went away immediately.

    What I notice is when mixing Sodium Hexametaphosphate it hardens like toffee and takes quite awhile to melt away.
    I am using 2 litres of hot water , 10 grams SH and 200 grams Sodium sulfate .

    Then I am adding 8 litres of 70 degree of water to make my working solution.

    Why is the SH Clumping and going to this toffee like state. Am I mixing it too hot?? 120 degrees.

  4. #24

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    Last year I was having problem with my clearing agent and water, I was getting scum (white deposits) on final prints even after proper wash.
    What you were experiencing was calcium sulfite being precipitated from hard water. Your solution was a correct one and any calcium chelating agent could be used. I would suggest dissolving the sodium hexametaphospahe first in a small amount of hot water and then adding it to the rest of the solution.

    I would also suggest acidifying your clearing bath with sodium bisulfite as in the formula given below.

    You could also use the following formula which is very close to Kodak's Hypo Clearing agent.

    Distilled water (50°C) …………………………………………… 750 ml
    Sodium sulfite (anhy) ……………………………………………… 100 g
    Sodium bisulfite …………………………………………………………… 25.0 g
    EDTA, Na4 ……………………………………………………………………………… 2.0 g
    Sodium citrate ………………………………………………………………… 5.0 g
    Distilled water to make ………………………………………… 1.0 l
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

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  5. #25
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    Instead of Sodium Metabisulfite and Hexametaphosphate one can simply add Citric Acid to the milky clearing bath. Not only does it form a nice buffer with Sulfite between pH 6 and 8, the Citric Acid also works as chelating agent for all these ions which tend to form white scum with Sulfite or Carbonate, and it dissolves easily in water.

    Instructions for making such a mix are very simple:
    • Prepare working solution of hypo clearing agent with Sodium Sulfite, Sodium Carbonate (or whatever your recipe says) and tap water.
    • The mix will be milky depending on your water hardness. Now add Citric Acid (anhydrous, monohydrate, it doesn't matter) until the working solution clears. Don't add too much Citric Acid or your bath will smell from SO2. If it does, add Sulfite or Carbonate to raise pH back to where it doesn't smell.
    • Done!
    Trying to be the best of whatever I am, even if what I am is no good.

  6. #26

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    I think what Rafal wants to investigate is whether sodium sulfite will do some of the actual fixing on its own, thus making the wash-aid bath a kind of "mini" second fix. I believe he wants to single-bath fix and count on the wash-aid to take up some of the slack when the single fixing bath becomes exhausted. I.e., I believe he wants to use the fixer past its "for optimum permanence" limit and rely on the wash aid to get the print to "optimum."

    There are some references (Ilford data sheets, etc.) that mention that fixing bath capacity can be "increased" by using a wash aid.

    I would tend to be skeptical of relying on sulfite as part of the actual fixing process. First, the effect, if it exists at all, must be rather weak. Second, there is no way that I know of, nor any literature about, determining the capacity for a fixing bath using sulfite vs. not. Third, since fixer is much better at fixing than sulfite (if the sulfite does anything at all), it is simply easier and more secure to use the fixer to do the job and replace it as needed.

    Single-bath fixing and optimum permanence means discarding the fixer relatively often in order to keep the dissolved silver under the limit for optimum permanence. Two-bath fixing allows much more capacity (approx. 4x) while at the same time ensuring that optimum permanence is achieved. Why substitute a proven procedure for a questionable and experimental one? Just to not have to make room for another tray? Or to save a couple seconds setting up and pouring in the chemicals?

    A wash-aid has been shown to help in the washing process, especially for fiber-base papers, but it has not ever been in the mainstream as a fixer. There must be a reason for this; I'm sure Haist, Mees and many others would have recommended sodium sulfite for this purpose if it had been practical. I tend to conclude, therefore, that it is not.

    Best,

    Doremus


    www.DoremusScudder.com

  7. #27
    Bob Carnie's Avatar
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    You know I never noticed the bath itself to be milky, just at certain times of the year the prints would exhibit a white scum after washing.

    thanks for your concise explanation.

    Quote Originally Posted by Rudeofus View Post
    Instead of Sodium Metabisulfite and Hexametaphosphate one can simply add Citric Acid to the milky clearing bath. Not only does it form a nice buffer with Sulfite between pH 6 and 8, the Citric Acid also works as chelating agent for all these ions which tend to form white scum with Sulfite or Carbonate, and it dissolves easily in water.

    Instructions for making such a mix are very simple:
    • Prepare working solution of hypo clearing agent with Sodium Sulfite, Sodium Carbonate (or whatever your recipe says) and tap water.
    • The mix will be milky depending on your water hardness. Now add Citric Acid (anhydrous, monohydrate, it doesn't matter) until the working solution clears. Don't add too much Citric Acid or your bath will smell from SO2. If it does, add Sulfite or Carbonate to raise pH back to where it doesn't smell.
    • Done!

  8. #28
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    Thank you Gerald. I do mix the sodium Hexametophospahte hot by itself but it immediately clumps together eventually it dissolves

    I will give your formula go and once again appreciate your advice.

  9. #29
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    Quote Originally Posted by Gerald C Koch View Post
    Whether the silver complexes are adsorbed in the emulsion or trapped in the the paper fibers is really immaterial in a practical sense.
    It might be important because the remedy could well be different. The emulsion responds to alkalis with swelling, which improves washing, while AFAIK paper base doesn't care all that much about pH. I would therefore assume that Carbonate based hypo clearing bathes work for film and RC paper while I don't expect them to be very beneficial for washing FB prints.

    When we discuss Silver Thiosulfate complexes we need to understand that there are two possible ways how they stick to fibers: it might be the Thiosulfate which somehow binds to the fiber, but I would rather suspect the Silver ion accepting some reactive group as another ligand.
    Trying to be the best of whatever I am, even if what I am is no good.

  10. #30

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    Quote Originally Posted by Doremus Scudder View Post
    I think what Rafal wants to investigate is whether sodium sulfite will do some of the actual fixing on its own, thus making the wash-aid bath a kind of "mini" second fix. I believe he wants to single-bath fix and count on the wash-aid to take up some of the slack when the single fixing bath becomes exhausted. I.e., I believe he wants to use the fixer past its "for optimum permanence" limit and rely on the wash aid to get the print to "optimum."

    www.DoremusScudder.com
    If this is indeed what Rafal is looking for, not likely to work very well. Haist briefly discusses Sodium Sulfite under "other fixing agents". As we know from film developers, Sodium Sulfite is a silver halide solvent, but it is a weak one. Further, its effectiveness depends on the type of silver halide. It works better on Silver Chloride than Silver Bromide, for example. So my half-educated guess is it wouldn't work very well on current chlorobromide papers, and Haist does not dwell on it for more than half a page. There do appear to be some more interesting potential alternatives to Ammonium Thiosulfate. Haist briefly discusses some compounds that under high pH conditions can fix materials in as little as 15 seconds and render the resulting complexes so soluble only a short water rinse is required for washing. Most of the chemistry he talks about there is beyond my understanding so I can't say much more on that. He probably couldn't say much more either, depending on what kind of fancy stuff Kodak was working on

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