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  1. #21
    jstraw's Avatar
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    Ok, I won't go nuts. If I don't exceed 2x TTC, do you think I'll be ok?

    I want to thank you all for your input.
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  2. #22

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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 only sensible way I know to do this is with the silver-estimating paper I mentioned. Unfortunately the typical test papers are not good at identifying silver levels much below about 1 g/l. Kodak once published a method to increase the sensitivity with a 30-second immersion, but it required "calibration" using a lab that could run silver analyses. (I don't think the method is published anymore.)

    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.
    I agree completely with this test to find when fixer "is shot." My issue is this: if you are trying to keep a low silver level in the final fix tank, say under 1/2 g/l, I doubt this test will show it. (I'm guessing, as I've never done fix-time vs silver content tests, but I'm very doubtful.)

  3. #23

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    Quote Originally Posted by Photo Engineer View Post
    I have never felt that I had to use 2 "tank" fixing except in production situations. It is just too much hassle to me.
    Hi, my main experience has been in production situations, but primarily color neg and print. From my considerable experience with effluent control, I can say that it would be extremely difficult for a lab to get silver in the effluent under, say 2/10 milligram/liter (not an unusual regulated number), without using multi-stage fixing. In fact, this is why "washless" mini-labs were introduced; low flow counter-current "rinses" were used, such that the total volume was small enough that one could afford to have a waste handler take it over.

    If one is small enough that they are unregulated (or perhaps no one is looking at your effluent), and the chemical costs are insignificant, then it's probably not an issue.

    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.
    I don't have any useful knowledge about the effect of these. Aside from what you (PE) say, about the only thing I'd have to go on would be Kodak literature describing a two-stage fixing system. In my mind, this is an endorsement of the system. (At least when Kodak sold B&W papers.) If one ignores any HQ/Metol retention issues, I would imagine that the same modeling methods I've successfully used for silver in color systems would be equally valid for B&W.

  4. #24
    Photo Engineer's Avatar
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    Bill, a Silver estimating solution is better than ANY paper. Just one drop on the border of a print will prove my point.

    I have worked with systems capable of zero pollution and unrestrained pollution and have compared both from the POV of impact and cost. So, I am glad that you can agree with me on some points.

    BTW, the reference to HQ retention is in Haist for those interested.

    PE

  5. #25
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    PE, do solutions like Agfa's Sistan deal with the residual silver in prints in a meaningful way?
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  6. #26

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    Quote Originally Posted by jstraw View Post
    Ok, I won't go nuts. If I don't exceed 2x TTC, do you think I'll be ok?



    I want to thank you all for your input.

    Forgive me for this, but I'm going to put a question back on you. If your final fix silver concentration went up to, over 1 g/l, would this be a problem for you?

    My point is that checking the first fixer for "exhaustion" doesn't really say very much about the silver level in the final fix tank. My GUESS is that it COULD exceed the number I gave without you knowing it. Given that there recommended numbers have been published, it would be nice to know what you actually have. (Silver estimating papers are the only sensible method I know for a small user, like most people here; even for a pro lab.)

    Without any knowledge about this, it's probably best to periodically test the actual film/paper for adequate washing (and perhaps fixing). Note post #11, where PE said, "...but I have found that the retained Silver test and the retained hypo test are the best."

  7. #27

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    Quote Originally Posted by Photo Engineer View Post
    Bill, a Silver estimating solution is better than ANY paper. Just one drop on the border of a print will prove my point.

    I have worked with systems capable of zero pollution and unrestrained pollution and have compared both from the POV of impact and cost. So, I am glad that you can agree with me on some points.

    BTW, the reference to HQ retention is in Haist for those interested.
    Hi, I think we may be talking about different things with "silver estimating paper." I am talking about a (former?) Kodak product named "Kodak Silver Estimating Paper." It is intended to be dipped into either fixer or bleach-fix, then rinsed off and compared to a color chart on the package. It is a rough guide, where one can say "it looks like my fixer is running about 3 or 4 g/l silver," for example.

    I don't question that tests on the final processed material are the ultimate arbiter. But for any kind of volume, I think it's better to set up a process with certain aim points. Once you verify that results are ok, then simply keeping the process nailed down should mean that all of the product is ok.

    My experience with "pollution" is not as in R&D, but rather an end user of, for example, methods designed by Kodak researchers, who then published papers, which were then the basis of equipment constructed by people such as CPAC. Anything that was published by SPSE or IS&T in the heyday of effluent control, we considered as an option. I was in a position to be part of a group which could evaluate these systems, justify them, then oversee installation and operation. There were always shakeout problems, partly because the scale was much larger than the researcher's pilot tests (things don't always scale up so well).

    ps: I probably agree with you on most things (that I know something about), but just don't come out and say that I agree. So you only hear from me when I disagree.

  8. #28

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    Quote Originally Posted by jstraw View Post
    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.
    That's exactly what it means. You replace bath one with bath two. It becomes your new first fix and has the same capacity as the original bath one.

    You have to understand the idea behind two-bath fixing: The first several prints through fix 1 get adequately fixed there. Fix 2 is hardly used at all for these. As fix 1 approaches capacity (note I don't say exhaustion), there are more complex silver compounds getting carried over to bath two than before, but, these are quickly broken down by the relatively fresh fixer in bath 2. By the time fix 1 reaches capacity, bath 2 is barely getting started, but it has ensured that the prints you've put through it have a really low level of residual silver.

    Quote Originally Posted by Photo Engineer View Post
    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
    You can, as PE does, just use a single fixing bath and get as good results. The problem is (and I believe that this is the problem you are interested in), is that the fixer is not used at all efficiently. Haist and others point out that, especially for prints processed for maximum permanence, i.e., residual silver in the fixer at levels of 0.2-0-5 g/l, fixer capacity is quite small. Two-bath fixing allows the fixer to be used more fully.

    As for retention of developing agents, etc., I imagine that this is the reason for only using two-bath fixing through seven cycles before discarding. I rarely use my fix for more than a couple of cycles anyway, preferring to err on the side of caution. I would think, however, that with an adequate stop and first fix, that the carry-over of developing agents to fix 2 would be minimal enough to not cause a problem, even after it has become fix one and 70-80 8x10/liter have been run through it, there is still a fresh fix 2 after it and then a thorough wash.

    Quote Originally Posted by Mr Bill View Post
    ... My point is that checking the first fixer for "exhaustion" doesn't really say very much about the silver level in the final fix tank. My GUESS is that it COULD exceed the number I gave without you knowing it. Given that there recommended numbers have been published, it would be nice to know what you actually have. (Silver estimating papers are the only sensible method I know for a small user, like most people here; even for a pro lab.)

    Without any knowledge about this, it's probably best to periodically test the actual film/paper for adequate washing (and perhaps fixing). Note post #11, where PE said, "...but I have found that the retained Silver test and the retained hypo test are the best."
    Indeed, even two-bath fixing needs a control. That's why the retained silver test (for fixing) and retained hypo test (for washing) are necessary. Testing regularly while determining your capacities is of prime importance. Pushing your system to failure once or twice will give you an idea of about where maximum capacity is and what kind of safety margin is needed. After one has confidence that the regimen is doing its job adequately, testing occasionally (especially when one suspects the system has been strained, e.g., with a lot of high-key prints, etc.) should be adequate to ensure that prints are being fixed adequately.

    I would love a quick, easy and accurate test to determine the dissolved silver content of my second fix. I don't think one exists that is practical, so ST-1 it is!

    As for exhaustion of bath 1. I've always used recommended throughput minus a personal safety factor. I see suggested above that a film clip-test may be used to determine the exhaustion of a first fixing bath for prints. I've always been skeptical of using this film-based test for print fixer. I'd appreciate comments about how useful/accurate this method is. If it works well for print fixer too, I will simply start clip-testing my first print fixer the way I do my film fix. I wouldn't base print fixing times on the results, however!

    Best,

    Doremus

  9. #29

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    Quote Originally Posted by Doremus Scudder View Post
    I would love a quick, easy and accurate test to determine the dissolved silver content of my second fix. I don't think one exists that is practical, so ST-1 it is!
    Hi, my best answer to this is with the silver estimating papers. If someone has a copy of the old Kodak procedure, the method is well described. And ideally, you have a color reflection densitometer. The downside is that you need to pay a testing lab the fee to run silver analysis on a half-dozen samples, or so, so I'd guess a charge of a $100 or $150 (this is a wild guess). In the old days, these would have been run on an AA unit, but in more recent times, one of the chemists here (Kirk) says more likely on an ICP machine.

    Basically, you assemble a set of your own fixer samples, covering a range from, say, 1/4 gram per liter up to 2 or 3 grams per liter. Pick a certain size sample container - we used those little disposable Solo cups (maybe 3 oz?). Suspend the test paper, motionless, for 30 seconds. Remove and quickly rinse with fresh water, then dry under warm air. Read the density (I think a blue-filter reading was recommended, but visual would probably work.) At the same time, a duplicate set of samples goes off to the analytical lab. (Make sure they know what they're reading, and give them a general idea of the range.)

    As I recall, plotting the density vs silver content has a gentle curve, slumping off near the top; I don't remember exactly. It's probably accurate within about 10%, in the general range of 0.3 up to about 1.5 g/l, as I recall (fuzzy memory). To check unknown sample, do the dip test, dry it, read the density, then look it up on the graph. We used this method in a large photo lab for quite a few years, until we eventually got an AA unit in our chem lab.

  10. #30

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    Quote Originally Posted by jstraw View Post
    PE, do solutions like Agfa's Sistan deal with the residual silver in prints in a meaningful way?
    No, the intent of these treatments is to protect the silver image from atmospheric pollutants. Traditionally a print was briefly toned in selenium or gold to achieve this protection. Their effect is negated by a poorly fixed or washed print.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

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