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  1. #1

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    Alkaline fixer/wash times for FB paper

    I did a quick search and didn't really find anything so hopefully this thread isn't totally repetitive. An APUG member asked me a question about fixers recently and it reminded me of a subject I've wanted to discuss.

    Topic note: This concerns non-hardening, Ammonium Thiosulfate rapid fixers.

    We're told all things being equal, an alkaline fixer will wash out of paper significantly faster than an acidic one and that a hypo clearing agent isn't needed. Does anyone have hard data on this? I'm asking because based on what I think I understand from Haist I'm not convinced. However the chemistry is quite complex so I could easily be wrong.

    When a Potassium Alum hardener is included in a necessarily acidic fixer, it is true that a lower pH fixer is harder to wash out. I wonder if the notion alkaline fixers wash faster is an oversimplified extension of this (ie wash rates keep increasing as pH is elevated).

    1. The emulsion
    Given a non hardening Ammonium Thiosulfate fixer, my understanding is the most efficient washing will occur if the fixer pH is increased to the isoelectric point of the gelatin (~4.9), with no real benefits above that point. Am I wrong?

    2. The paper base
    My understanding is the rate of washing the thiosulfate and silver thiosulfate complexes out of the paper fibers, baryta etc. is essentially unrelated to the pH of the fixer. Am I wrong? This would also appear to contradict the hypo clearing non-requirement with alkaline fixers.

    If I'm reasonably correct about (1) and (2) above, faster paper washing would not be an advantage when using an alkaline fixer. The remaining benefits are no image bleaching with overfixing and possibly higher (?) capacity.

    Thoughts?

  2. #2

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    I've been thinking about this very issue lately as well.

    I'm hoping some of the fixer experts (PE, et al.) chime in here. I have doubts about the higher capacity claims as well. And, while we're at it, we might as well drag the Ilford archival sequence into the discussion. Lots of fodder here for an interesting thread. I'm looking forward to it.

    FWIW, I don't have an issue with washing longer, which I usually do, and I do residual hypo and silver tests (HT-2 and ST-1) to make sure my work-flow is not grossly out of whack, but I haven't taken the process to the limits in years, and certainly not with an alkaline fix like TF-4 or TF-5.

    Best,

    Doremus

  3. #3

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    Quote Originally Posted by Michael R 1974 View Post
    I did a quick search and didn't really find anything so hopefully this thread isn't totally repetitive. An APUG member asked me a question about fixers recently and it reminded me of a subject I've wanted to discuss.

    ...

    Thoughts?

    Hi, I guess the lack of responses so far (Doremus aside) implies that there is not a wealth of information out there on this sort of thing. I don't have personal knowledge on this, nor any good tech papers, nor am I a chemist. My main experience has been with color neg/print paper, in very high-volume operations.

    Keeping in mind my limitations, my understanding is that with B&W materials the gelatin is the easiest part to wash. After this, there is some tendency for thiosulfate (and related) ions to adsorb to silver grains; I'm not sure how difficult or necessary it is to completely remove this. I take it that various wash aids might tend to bump off and replace this thiosulfate with their own ions. This is my own personal interpretation, not supported with hard literature references.

    Regarding the paper base (not RC paper), Mason, in Photographic Processing Chemistry (1966) says, "...the removal of further thiosulphate from the base is a lengthy process by washing alone. The reason for this retention is that the thiosulphate ions have to pass through the cell walls of the paper fibres, which are often protected by sizing materials, etc." There is no mention of pH in this respect, except mentioning that "washing is slowed down appreciably if an aluminium hardening fixing bath has been used." (we know that such a hardening fixer has a fairly low pH.)

    Mason mentions wash aids, saying, "The phenomenon was first fully investigated in 1956 by Crabtree, Henn, and King who showed that the introduction of a short soak in certain salt solutions between fixation and washing greatly increased the rate of the subsequent removal of thiosulphate and silver complexes." But again, pH is not mentioned.

    I don't know if there IS any modern research on this, other than occasional articles by photographers who have done their own tests for residual thiosulphate.

    To throw one further complication in there, about 10 years ago there where some internet articles to the general effect that it may be desirable to maintain some low level of residual thiosulfate - that is, to limit the washing. A couple of technical papers were referenced, of which I read one. It was regarding micro-film, where (per my fuzzy recollection) small "redox" spots tended to form on certain films, but not others. And that a tiny amount of residual thiosulfate and iodide existed in the unaffected films, but not in the others. (Don't put too much stock in my exact account of this.) I didn't investigate any further, as my day job didn't involve B&W by this time, only color, but you can probably find further info via a web search. My point is that it may be possible to over-wash.

    Perhaps someone will have some better information on the relation of fixer pH to washing. (I mean with some sort of solid basis other than "it's well-known," or that sort of thing.)
    Last edited by Mr Bill; 05-09-2013 at 06:06 AM. Click to view previous post history.

  4. #4

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    I am hoping that some savvy chemists can answer these questions. Please!!!! How do you determine your fixer capacity. is there a way to determine? with some sort of "measuring system" when it is time to make new fix? Or does every one, like me, keep a tally sheet of "so many" 810's per liter, once you reach the suggested "limit", you then pitch it, and make new? I find this to be at best a guessing game, not archival, and at worst, wasteful. You are either using your fix "beyond" sound practice, or you not using it enough and throwing GOOD chemistry down the sink!!! I hate to guestimate!!!

  5. #5

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    Michael, maybe you'll find some answers to your questions in this thread: http://www.apug.org/forums/forum37/1...ll-fixers.html

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    Hi Doremus, Mr. Bill, thanks for the feedback so far. I have a few additional thoughts:

    1. When discussing ion exchange clearing baths as an aid to washing (HCA), Haist briefly mentions research pointing to the addition of clearing agents such as Sodium Sulfite, Sulfate and other compounds directly to the fixer, which could potentially eliminate the need for a separate HCA bath to improve washing/washing rates. At the time the book was written I guess there wasn't much on this yet, and it still concerned acidic fixers. Perhaps this is the "secret" behind purported faster washing with fixers like TF-4 or TF-5 rather than alkalinity per se (TF-5 is just slightly acidic). Perhaps people then incorrectly assume any alkaline fixer will wash out faster because TF-4 does.

    2. Haist mentions research and experiments that showed treatment of the print in an alkaline solution after fixation can help washing. However I find the section unclear. It seems to relate mostly to the emulsion and again deals with bringing the gelatin up to the isoelectric point. But it is not clear why it might help to raise the pH beyond the isoelectric point, nor are actual pH values discussed. Swelling is mentioned in reference to both the emulsion and the paper base, but it seems swelling can actually slow down the rate of washing the emulsion due to a longer diffusion path. It is not entirely clear to me what the conclusion is regarding the rate of washing the paper base. Swell seems to help, but swell vs what? Vs the state of the paper when it comes out of the acid fixer? Or vs a neutral state?

    3. Anchell makes the statement alkaline fixers wash faster than acidic ones. He doesn't really explain why other than to use laundry soap as an analogy, saying alkaline soap washed out of clothing fibers faster than an acidic detergent would. In Anchell/Troop the authors also cite faster washing as a benefit of alkaline fixers, although this is in relation to film, not paper (The Film Developing Cookbook).

  7. #7

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    Quote Originally Posted by gzinsel View Post
    I am hoping that some savvy chemists can answer these questions. Please!!!! How do you determine your fixer capacity. is there a way to determine? with some sort of "measuring system" when it is time to make new fix? Or does every one, like me, keep a tally sheet of "so many" 810's per liter, once you reach the suggested "limit", you then pitch it, and make new? I find this to be at best a guessing game, not archival, and at worst, wasteful. You are either using your fix "beyond" sound practice, or you not using it enough and throwing GOOD chemistry down the sink!!! I hate to guestimate!!!
    Gzinsel, the general consensus is that you can use fixer until the silver content reaches some predetermined level. There are several sets of published recommendations for this; for commercial work a higher level is allowed, for maximum permanence a lower level.

    The problem is that it's difficult to know how much silver you've built up. This is why the general recommendation for counting the sheets. For a little better accuracy, you can purchase "silver-estimating papers." These are little test strips which you dip in the fixer, then compare the shade of the test paper to a reference; it gives you an approximate idea.

    If you're not already using a 2-stage fixer, you should look into this. It lets you get a lot more use out of your fixer, with a bigger safety margin to boot.

  8. #8

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    Quote Originally Posted by Michael R 1974 View Post
    Hi Doremus, Mr. Bill, thanks for the feedback so far. I have a few additional thoughts:

    1. When discussing ion exchange clearing baths as an aid to washing (HCA), Haist briefly mentions research pointing to the addition of clearing agents such as Sodium Sulfite, Sulfate and other compounds directly to the fixer, which could potentially eliminate the need for a separate HCA bath to improve washing/washing rates. At the time the book was written I guess there wasn't much on this yet, and it still concerned acidic fixers. Perhaps this is the "secret" behind purported faster washing with fixers like TF-4 or TF-5 rather than alkalinity per se (TF-5 is just slightly acidic). Perhaps people then incorrectly assume any alkaline fixer will wash out faster because TF-4 does.
    Don't forget that C-41 process uses a near-neutral (~pH 6.5) fixer, and it was introduced long before Haist's book. So I'm pretty sure the Kodak folks were well familiar with non-acidic fixers.

    Just about every common fixer (thiosulfate) contains a pretty fair amount of sulfite already, so I'm not sure how much would be needed to improve washing. I suspect it wouldn't be economical.

    I don't know anything about the fast-washing fixers, so no idea why.

    2. Haist mentions research and experiments that showed treatment of the print in an alkaline solution after fixation can help washing. However I find the section unclear. It seems to relate mostly to the emulsion and again deals with bringing the gelatin up to the isoelectric point. But it is not clear why it might help to raise the pH beyond the isoelectric point, nor are actual pH values discussed. Swelling is mentioned in reference to both the emulsion and the paper base, but it seems swelling can actually slow down the rate of washing the emulsion due to a longer diffusion path. It is not entirely clear to me what the conclusion is regarding the rate of washing the paper base. Swell seems to help, but swell vs what? Vs the state of the paper when it comes out of the acid fixer? Or vs a neutral state?
    If Haist says research showed that, I'm sure it's legitimate. Too bad he didn't (or couldn't?) say more about it.

    I think that iso-electric points vary with the exact gelatin, so maybe it's wrong to give a certain pH value. Just guessing. If the main issue is the amount of emulsion swell, the solution makeup is probably more important than pH. Lloyd West of Kodak published a paper, "Water Quality Criteria" in 1965. He showed graphs of emulsion swell in various solutions, and by far the greatest amount of swell was in distilled water, more so than in a color developer.

    With modern materials, I'm not sure that they swell very much; I don't think so. There used to be special hi-temp fixers, etc, with a high salt content to limit swelling. But since modern color processes run at fairly high temp, you would guess that these are heavily pre-hardened. I'd guess that B&W emulsions are also, but again, this is guessing on my part.

    3. Anchell makes the statement alkaline fixers wash faster than acidic ones. He doesn't really explain why other than to use laundry soap as an analogy, saying alkaline soap washed out of clothing fibers faster than an acidic detergent would. In Anchell/Troop the authors also cite faster washing as a benefit of alkaline fixers, although this is in relation to film, not paper (The Film Developing Cookbook).
    Yep, that argument doesn't carry much weight with me. Back when I was a kid, I would have ate that up, but having spent a good part of my adult working life working with various process systems and the like, I've heard a large amount of B-S. So in the real world, I always ask people, "how do you know that?", then "Are you sure?" To really confirm what they know, the "beer test" is used, ie., would you bet beer on that? For some reason, even though they would be glad to buy you a beer, nobody wants to risk losing one in a bet.

  9. #9

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    I think I'll just stick with good old Ilford Rapid Fixer.

  10. #10

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    My question would be: where is the point of diminishing returns on washing, and why would anyone want to leave the print with a softened gelatin when it was all done and dried? I've not been convinced that plain ordinary Kodak Fixer is still not the best way to go, and following Kodak's washing procedure. So far, prints I made 40 years ago are exactly as they were then. At that rate, it would have to be 200 years before they went sour.
    I chimed in because I am making a switch of all procedures toward 8x10 and FB printing. Thank you.

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