Double Fixer Debate

Discussion in 'B&W: Film, Paper, Chemistry' started by Lobalobo, Feb 16, 2009.

  1. Lobalobo

    Lobalobo Subscriber

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    In a separate thread, I got excellent advice on how to tell whether the six-month old fixer concentrate I had was still good. In the course of that thread, I was advised to use double fixer bath on prints, and I have since discovered advice to do the same on film. But looking into this further, I note that some think that double fixer baths make sense in theory but add little in practice (or maybe even hurt). Rather than invite a repetition of this debate, although I welcome learning more, I wonder whether even proponents of a double fixer bath would recommend that it be used in a very, very-low-volume process such as mine. For film, I never use the same fixer on more than six 4x5 negatives, each sheet separately in the fixer, or a single role of 12 6x6 images. For prints, 16 ounces of working solution for no more than 12 5x7 RC sheets each processed in the fixer one at a time. So neither exhaustion or failure to get the solution on the surface is an issue for me. Is a double fixer bath still recommended? Thanks.
     
  2. Anscojohn

    Anscojohn Subscriber

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    I use a double fixer bath (sometimes three) but only on fiber-based prints. Everything I learned about everything, though, appears to be challenged nowadays.
    So, what the heck. My fifty year plus negs still look ok, though. My Dad's 75 year old negs still look o.k. One fixer bath, only.
    My FB prints from the early 1960s have held up well, even the ones before I began the two bath process recommended by Eastman. Dad's from the 1940s look just fine. I guess I'll stick to what I have been doing, thank ya verah much.

    I expect with RC prints it doesn't make any difference. No one has seen what the RC substrate will look like 50 or 75 years from now, anyhow. I, myself, can't be bothered with RC paper except for work prints and other uses that do not matter to me.
     
  3. edtbjon

    edtbjon Member

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    In my mind the idea is to get the material completly fixed. I can understand why some people use the regime with double fixer baths for FB prints using old-style (non-rapid) fixer. Some FB materials are more sensitive to the quality of fixer etc.
    But with RC paper and film there should be no need for this. Rather the quicker the better, as the paper base/film base doesn't come into play.
    Last Lobalobo, in my opinion, you are waisting your fixer much too early. It still have a lot of life left in it, as it has hardly been used at all. There is maybe 75% left in it. (You don't mention which type of fixer you are using, nor if you dilute it more than e.g. 1:4 for film.)

    //Björn
     
  4. GeorgesGiralt

    GeorgesGiralt Member

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    Hi !
    IMHO, the rationale here is not correct fixing.
    In fact, the recent studies (in the 70's and after) about fixing where done to speed up WASHING and doing so reduce water consumption.
    Studies have shown that film is really easy to wash because film base does not get water and fixer residues in it, so you only have to wash the gelatin layer which is very small in volume and does not contain a lot of water. The same approach goes for RC paper because the fiber base is protected by a plastic sheet.
    The problem is to wash fiber base paper. This problem is complicated by the fact that the fibers in the paper hold fixer by products tightly. So the idea had been devised to reduce the time the paper soaks into the fixer to reduce the amount of by product to wash out of the paper base. Ilford had made a lot of studies on that mater and devised a fixing and washing sequence where a fiber paper is fixed for 30 sec to 1 min in strong fixing bath (rapid fixer, used at film concentration) and a washing where the paper is not soaked for long but the water is changed instead (this is because an equilibrium point is rapidly reached and the fixer by product can't get out of the paper once the water has got some, so it does not matter how long you'll soak the prints, they simply won't wash...)
    A German guy had make a study washing film and measuring the amount of fixer by products found on the wash water after a few washes, and he shown that after 5 change of water, there is no fixer left. (provided you drain correctly the tank between washes)...
    So, I'm not a chemist, nor a researcher in a photographic lab. So I stick with what Kodak or Ilford or Agfa scientist have found. And this is :
    Use rapid fixer at film concentration, be very conservative regarding fixer exhaustion (follow manufacturer guidelines) and wash by using two wash bathes : put the paper in a tray full of water, during that time, fill another tray, transfer each print from the first tray to the second one, squeezing as much water as you can, when done dump and refill first tray and repeat the process. You'll soon have properly washed print at a fraction of the water you used previously. (this method was told to me by a French B&W reputed printer which had it tested by scientist for residual fixer by products in the paper base in order to sell archival prints at the least cost possible because, in France, water is metered and not cheap)....
    Hope this helps clarify things a little.
     
  5. Ian Grant

    Ian Grant Subscriber

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    Lobalobo, you should read Ilford's data sheets to get an idea of fixer capacity, for film it's quite high 24 rolls of 35mm/120 per litre, that's roughly 96 sheets of 5x4 film.

    The Ilford figure is 80 sheets 10x8 of RC paper per litre for Hypam or their Rapid fixer, which is roughly 180 5x7's, or 86 5x7's per 16 oz (US) working solution, so you're under using your fixer.

    Two bath fixation isn't really necessary for films & RC papers, however it's the best system with Fibre based papers as it gives good capacity as well as ensuring good archival permanence.

    Ian
     
  6. dancqu

    dancqu Member

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    The issues are the mediums' tolerance for silver and the
    fixer's chemical capacity for silver. The greater the volume
    of fixer the greater amount of film or paper may be cleared.
    So, a greater amount of non-image silver may be removed
    from the emulsions as the volume of fixer is increased.
    And that is with any given amount of chemistry.

    The most efficient use of a fixer occurs at point where the
    chemistry's capacity for complete dissolution of the retained
    silver salts equals the medium's volumetric limit. That is where
    the chemistry's limit equals the volumetric limit. There are two
    limits. Many think only of fixer capacity being dependent upon
    the strength of the fixer. Fixer capacity also has limits of
    dissolved silver per unit volume.

    On a volumetric basis, film and IIRC to a lessor extent RC
    papers can make good use of the chemistry in a fairly strong
    fixer. FB though has a low volumetric tolerance for dissolved
    silver. For best use of the chemistry, fixer volume must be
    high; that is the fixer's strength should be low.

    Film or FB, I use only very dilute fixers. Used one-shot they
    are nearly exhausted after one roll or sheet or sheets at-
    same-time processed. Dan
     
  7. OP
    OP
    Lobalobo

    Lobalobo Subscriber

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    Thanks to all. All of my wet darkroom processing is for contact prints of 4x5 Efke 25 negatives taken with a f/150 pinhole camera. The negatives are processed in D76, then placed into a mask that centers the image on 5x7 paper, then put in cheap plastic thin-black-aluminum 5x7 frames. I like the results from this low-tech, simple process. It had not occurred to me that the look would be much different on fiber paper, but I suppose I should try it. (But then again, I'd need a filter, which would be difficult as my current form of exposure is a white, frosted 7.5w bulb in a desk lamp aimed at a white wall--the light bounces around the small bathroom, including off a mirror, but at 20 seconds, I get good results; I worried about clouding, based on a post I read, but couldn't figure out how that would be an issue--am I missing something?)

    As to why I throw out the chemicals so soon, it is not because I think they are exhausted; it's because I never process more than six negatives or 12 prints at a time and then the darkroom is put away for a week at least. (I will start to develop medium format film taken on my Brownie Hawkeye--sticking with the low-tech theme--but there too, I'll develop no more than one, or maybe two, rolls per week.) Thanks again.
     
    Last edited by a moderator: Feb 16, 2009
  8. Bob Carnie

    Bob Carnie Subscriber

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    I like using a two bath method for fixing my fibre prints and I use a rotation method .

    Basically the first fix takes all the crossover of acid stop, the second fix is always fresh mixed fix which takes two thirds of my fixing time total.
    After the printing session the first fix is put into the silver recovery system, and if I have not over used the second fix , it is bottled and used as the first fix my next printing session.
    On really heavy days both fixes go into the recovery unit and next session is all fresh.

    I have always thought the crossover from the stop can ultimately hurt the fix therefore a first fix is a buffer , then the fresh fix does the real work. Using a single fix may exhaust faster with all the acid coming from the stop , but maybe some of the chemical guru's could answer that one.
     
  9. Ian Grant

    Ian Grant Subscriber

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    In reality the first fixer bath should do virtually all of the work, the 2nd bath's job is to make sure that there are no insoluble silver/thiosulphate complexes left in the paper.

    Ian
     
  10. DWThomas

    DWThomas Subscriber

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    Golly, I didn't realize there was a debate!

    But anyway, I do very small quantities, mostly fiber base. When I print a few test prints, maybe 5x5 inches or so, I use a single bath. I save that and use it for the first bath of two when I do an even smaller quantity of larger prints. After that, it's all likely to get tossed, as it may be months before the next session.

    I used to just use a single bath back in the 19-ought-sixties and those appear to be hanging in there OK.

    DaveT
     
  11. edtbjon

    edtbjon Member

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    The mixed fixer (and the stopbath) doesn't go off in any noticable way in at least a year or so. That could even be 5 years or so.
    Simply do the clearing time test to see if the fixer is OK. (Discard the fixer when the clearing time is double that of a fresh mix.)

    //Björn
     
  12. dancqu

    dancqu Member

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    That is important. The first bath should be the one to
    load up on the non image silver. The second bath is to
    be as little loaded as possible. Makes for very clean
    prints and a clean first fix when it's turn comes. In
    order to keep silver levels low and allow for
    sooner turn over I think no less than the
    1:9 dilution appropriate.

    Using Ilford's guide lines for capacity a liter of their
    rapid fix at paper strength, 1:9, is good for 20 8x10s;
    at film strength, 1:4, 40 8x10s. At 1:19 a liter of
    working strength will do 10 8x10s.

    That last dilution is the equal point I referred to in my
    just previous post this thread. The fixer at that dilution
    has just enough chemistry and just enough volume to
    fully fix 10 8x10s and those 10 to Ilford's standard
    for optimal longevity. Ilford's standard for fixer
    retained silver at that point is 0.5 grams/liter.

    Grant Haist's 0.2 grams/liter allows for only
    4, 8x10s. Commercial limits are higher; Ilford's,
    2 grams/liter; 1:4 dilution, 40, 8x10s/liter. Their
    guide lines; 200 8x10s/liter of concentrate. Ilford
    uses pint averaging when determining capacity.

    I, with my very dilute one shot fix, use worst case.
    An unexposed sheet is tested for minimum needed
    chemistry. The Ilford version of the HT-2 test is
    used. NO stain is good enough. Dan

    A good use of chemistry is the two bath fix. As the
    first bath nears capacity it is mandatory to reduce
    the prints retained load of silver laden fixer. The
    second fixer does that and assures complete
    fixation. Dan
     
  13. PVia

    PVia Member

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    Why not a running water stop, and a one-bath alkaline fixer ala TF4?
     
  14. drazak

    drazak Member

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    I feel that a double fixer bath is definitely the way to go if you're doing FB prints, if not, just have one fixer bath. I think that a lot of you have heard some advanced chemistry that you didn't understand, probably due to it not being explained very well. In fixer there are ions of thiosulfate, S2O3^2- that form what's called a complex with the unreduced silver halides in the paper or film. The unreduced silver halides in the paper are not soluble, however their complexes with S2O3^2- are very very soluble, just like S2O3^2- is itself. The complexes formed may be damaging the paper many years later as they start to oxidize and turn colour, a second fixing bath of the same type will provide conditions where the silver complexes carried over may dissolve, there are many factors regarding the dissolving of certain complexes in solutions containing a component, and needless to say it is fairly complex. The second fixer bath will take care of all of the silver complexes carried over in/on the paper, much better than running water. The resulting carryover should only be sodium or ammonium thiosulfate which is readily soluble in a water wash. many of the washing methods, with big archival washers and running water do not allow sufficient time for the carried over S2O3^2- ions to reach equillibrium between what is in the paper and what is in solution, however as the water washes the carryover and water moves over the paper, the ions diffuse through the water as they are dissolved. A water change method of washing FB paper fixed in a two bath method may indeed be viable if there were very few silver complexes still left on the paper, those are what you have to worry about and as I understand, most of the fixer residue testing agents do not test for or find the silver complexes. I hope my answer has not contained too much chemistry for you!

    Ben

    P.S. I don't mean to downplay the dangers of leaving S2O3^2- ions in the carryover residue on your paper, however I feel that the dangers of silver complexes are going to much outweigh those of S2O3^2- ions.

    P.P.S. I realized that I was bouncing back and forth between S2O3^2- and thiosulfate, it's the ion that forms a complex with silver to fix your paper, there's a ton of it in fixer, those of you that mix your own chemicals would know, you put over a pound of it in a litre of water.
     
  15. dancqu

    dancqu Member

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    TF-4 or what ever, Kodak, Ilford, and ..., the two
    bath fix is the better option for reasons I and
    others have given. Figure about double the
    print capacity with a two bath fix.

    I fix using one-bath but use a very dilute fixer
    one-shot. The fixer's dissolved silver amount
    is Very low. Dan