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  1. #11
    Photo Engineer's Avatar
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    Lots of long answers here but I have found that the retained Silver test and the retained hypo test are the best. The Formulary uses Kodak formulas for making them up. The exhausted fixer test is virtually useless especially when using papers. Testing for 2x clearing time in film is quite useful as well.

    I spent years on the subject of fixers and find the subject fascinating.

    Oh, the Formulary sells a full line of film and paper solutions for development, stop, fixing and post wash testing. I have never used a hypo eliminator or any such was aid. They are virtually useless and increase the pollution factor.

    PE

  2. #12
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    Isn't it a trade off? If I don't use a wash aid, won't I have to use much more water to wash out fixer?
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  3. #13
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    It is a trade off between dumped salts from the wash aid and the increased water with a small amount of hypo and silver complexes. However, in the larger view, you have to get rid of the hypo and silver complexes so it boils down to the pollution "demand" imposed by the wash aid.

    And, modern day RC papers take less washing anyhow.

    For those who yelp about FB papers, they are more heavily calenared nowdays and thus the papers are less porous. If you don't believe me, check a modern FB such as Ilford MGIV and comapre it with a 20 or 40 year old sample of say Kodabromide. There is quite a difference.

    PE

  4. #14
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    Quote Originally Posted by Doremus Scudder View Post
    Michael,

    Fixer doesn't have an exhaustion point that's really easy to nail down. I depends more on the amount of residual silver you are willing to live with in your film/paper and the amount of safety margin you want in your fixing regime so that you don't use fixer that is too full of unwanted silver compounds to fix with.

    Ideally, we could easily measure the amount of dissolved silver in a fixing bath accurately down to the small levels that are needed (e.g., 0.2g/l for optimum permanence for fiber-base prints). Unfortunately, this is not practical for the typical darkroom worker. This is why you need an adequate safety factor (read, you don't really want to work at the edge of exhaustion; it's just too risky if you want optimum permanence).

    My solution to get the most of my fixer while still ensuring optimum fixing is to use two-bath fixation whenever possible, even for film.

    For film, do a clip test on your first bath before each batch. I triple the time instead of doubling it; some modern films do take longer to fix due to the silver iodide in the emulsion, and a safety factor for film can't hurt, since it is on an impermeable base. This time I divide between the two baths. When the clearing time for the clip test is double that in fresh fix, bath 1 is sent to silver recovery and bath 2 takes its place. If you develop film regularly, then you can keep the system going for the full seven changes before the fixer is too old (see below).

    For fiber-base prints, don't take any chances, especially if you want optimum permanence. First, try not to overfix; use a minimum time and a safety factor on capacity. I use throughput as a guide and discard bath 1 somewhat before the recommended capacity is reached just to be sure. You'll still have a lot of silver in bath 1 to recover if you do this. It's just much better to err on the side of caution here IMO. I use 36 8x10 per liter as a maximum throughput (slightly less than Ilford's recommendation). If you use another fixer, read the manufacturer's recommendation. Again, when your capacity for the first bath is reached, replace it with the second. This can also go through seven changes till you should discard both baths and start over. Or discard when the maximum age of the fixer working solution has been reached, whichever comes first. Ilford recommends the following for fixer lifespan: 6 months in full tightly capped bottles, 2 months in a tank or dish/tray with a floating lid, 1 month in a half full tightly capped bottle or 7 days in an open tray.

    Test your system at the beginning and then regularly thereafter for residual silver using the Kodak ST-1 residual silver test to make sure your fixing to an acceptable standard (and do the HT-2 residual hypo test while you are at it to test if you are washing adequately as well). Both these tests are available from the Formulary (with different proprietary names, but the same tests).

    The above will give you peace of mind, get the most out of your fixer and ensure you aren't sending unused or partially used fix to silver recovery.

    Best,

    Doremus


    www.DoremusScudder.com
    I appreciate your help. I have a question about your recommendation for cycling 1st and 2nd fixer baths. You say "when your capacity for the first bath is reached, replace it with the second. This can also go through seven changes till you should discard both baths and start over. "

    When the previous second bath becomes the new 1st bath, what is the capacity? Surely it doesn't see the same 30 8x10s the original 1st bath got. Can you clarify?

    Thanks.
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  5. #15

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    Quote Originally Posted by jstraw View Post
    Quote Originally Posted by Mr Bill View Post
    ...check the silver concentration in the "clean" tank.

    I'm not sure what you mean by "clean tank."

    From your first post, I've taken it that you are using 2-bath fixing, that is, a first tank followed by a second tank. Since the first tank collects most of the silver, I call it the "dirty" tank. The second tank, with a relatively small amount of silver, I call the "clean" tank. (In the industry, the normal nomenclature would be "fix-1" and "fix-2").

    The reason I suggest checking the silver content of the final fix tank (the "dirty" tank, fix-2,etc.), is that you normally want to keep this below a certain spec concentration. If you look for "exhaustion" in the first fix bath, you really don't know much about the silver concentration in the final fix tank. It depends largely on how much solution carryover you have; this is the amount of solution the wet film or paper takes along with it. If you don't use squeeges between all the tanks, you probably can't "exhaust" the first fix bath before the second bath exceeds fairly low silver limits.

  6. #16
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    Quote Originally Posted by Mr Bill View Post
    From your first post, I've taken it that you are using 2-bath fixing, that is, a first tank followed by a second tank. Since the first tank collects most of the silver, I call it the "dirty" tank. The second tank, with a relatively small amount of silver, I call the "clean" tank. (In the industry, the normal nomenclature would be "fix-1" and "fix-2").

    The reason I suggest checking the silver content of the final fix tank (the "dirty" tank, fix-2,etc.), is that you normally want to keep this below a certain spec concentration. If you look for "exhaustion" in the first fix bath, you really don't know much about the silver concentration in the final fix tank. It depends largely on how much solution carryover you have; this is the amount of solution the wet film or paper takes along with it. If you don't use squeeges between all the tanks, you probably can't "exhaust" the first fix bath before the second bath exceeds fairly low silver limits.
    I think you're telling me to pay the most attention to the second fix' silver content. It's a little confusing because it seems as though you just referred to the 1st fix as the dirty tank then the second fix as the dirty tank.
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  7. #17
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    You must remember that it is almost impossible to check a tank for Silver content. This is especially true when using the fix for paper.

    The most reliable test is "time to clear". Select a 35mm film type (whether you are using paper or not) and cut an unexposed roll into 2" pieces. Using fresh fix, determine the clearing time. Now, every time you make a run, do the same with another piece of film. When the clearing time is approaching 2x the original time, that fix (first or second "tank, tray or whatever") is shot.

    PE

  8. #18
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    Quote Originally Posted by Photo Engineer View Post
    You must remember that it is almost impossible to check a tank for Silver content. This is especially true when using the fix for paper.

    The most reliable test is "time to clear". Select a 35mm film type (whether you are using paper or not) and cut an unexposed roll into 2" pieces. Using fresh fix, determine the clearing time. Now, every time you make a run, do the same with another piece of film. When the clearing time is approaching 2x the original time, that fix (first or second "tank, tray or whatever") is shot.

    PE
    This makes the most sense to me. Presumably, the first tray will be shot first. The second tray will become the new first tray and so-on. Is that correct?

    Do you see an advantage to two tank film fixing?
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  9. #19

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    Quote Originally Posted by jstraw View Post
    I think you're telling me to pay the most attention to the second fix' silver content. It's a little confusing because it seems as though you just referred to the 1st fix as the dirty tank then the second fix as the dirty tank.
    You're right - I messed up my wording. I meant to call the second tank the "clean" tank.

  10. #20
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    I have never felt that I had to use 2 "tank" fixing except in production situations. It is just too much hassle to me.

    And, BTW, for good prints HQ and Metol retention are things to consider. As you re-use fix, these build up in the fix and there is NO test for them. So, be careful.

    PE

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