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  1. #21

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    Mike,

    Yes, there can be voltage variations that result in fluctuations in radiation virtually all light sources, including UV fluorescent tubes. This can vary a lot depending on house wiring, applicances on the circuit, and time of day, but in many cases the cumulated variation is more than sufficient to affect exposure. The best solution for this is to place a light integration system on your exposing unit. All platemakers, Nuarc 26-1k for example, have this feature.

    Sandy




    Quote Originally Posted by mikepry
    Now the new problem........................Has anyone ever noticed flucuations in UV output with a bank of BLB tubes? Are they sensitive to voltage flucuations? Thanks for all the good info guys I really appreciate it!!!!

  2. #22
    clay's Avatar
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    I think the developer temperature is just possibly exacerabating another problem. I regularly use potassium oxalate developer up to 160 degrees, and I have never had the problem being described. Perhaps some unusual tap-water-caused precipitation is being amplified by the use of hot developer.
    I just want to feel nostalgic like I used to.


    http://www.clayharmon.net - turnip extraordinaire

  3. #23
    mikepry's Avatar
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    I think you may be right Clay. My water is very hard and the water from my faucets in my darkroom is softened. But, at any rate, the lowering of the temp eliminated the crystals completely. Sometimes I want to step back and ask the question if there is sorcery or the like involved in this process???!!!! Things go along so smooth and all of a sudden out of nowhere here come the problems. Anyhow, as a young man, my father used to tell me when I would have frustrations helping him on his carpentry jobs..."If it was easy, anybody could do it." I am reciting this now!
    "EVERY film and paper is good .......... for something"
    Phil Davis

  4. #24

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    Quote Originally Posted by sanking

    1. Michael proposes using a weaker solution of potassium oxalate because this apparently gives better clearing in his condition. I am assuming he mixes the PO solution from well water rather than with distilled water?
    No, I am suggesting only that a lower concentration of developer will probably clear out of the paper to minimal levels faster, which could reduce the possiblity for the oxalate to accumulate as calcium oxalate, if that is actually what is happening.

    Generally you need no higher than about a 25% solution to develop well, so a 33% solution is a bit more concentrated than is necessary to do the job. No sense loading more oxalates into the paper fibers than is necessary to do the job, especially if there is a problem with calcium in the water.

    -----

    Clay mentions that he uses very high temperatures without problem, and I have also used the developer up to about 160-170 without this problem, but I don't do that on a regular basis.

    What does happen with the developer this hot is that it blows out the sizing in the paper rapidly. If this happens, the PO and other chemicals can penetrate deep into the paper and it will take considerable effort to get them completely out in the wash cycles.
    www.mutmansky.com
    B&W photography in Silver, Palladium, and gum bichromate.

  5. #25

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    Mike,

    How long do you develop in the PO? You may be able to shorten the develop time a bit to reduce the PO absorption as well.

    I think some people recommend 2 minutes or so, but I find that with warm or hot developer, one minute is perfectly sufficient, so I reduced my time in the PO to that.


    ---Michael
    www.mutmansky.com
    B&W photography in Silver, Palladium, and gum bichromate.

  6. #26
    mikepry's Avatar
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    Mike,
    I usually develop for 2 minutes. I found, by some reason I can't explain, that my prints cleared better going from 1min up to 2 min. on dev. time.
    "EVERY film and paper is good .......... for something"
    Phil Davis

  7. #27

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    Mike,

    The reason they clear better is that the developer is also a clearing bath, and a hot clearing bath is better then a room temperature clearing bath.

    I see this as another benefit of pulling the print out of the PO faster, though, because I don't want the PO fouled up with FO and pt/pd salts, so the quicker it comes out, the less the PO loads up with that stuff. It does mean a little more effort on the clearing bath end however, to ensure complete clearing.

    Once the moon aligns properly, you'll be back to making great prints again.


    ---Michael
    www.mutmansky.com
    B&W photography in Silver, Palladium, and gum bichromate.

  8. #28
    EricNeilsen's Avatar
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    Quote Originally Posted by sanking
    I prepare my PO solution just as Eric describes and I have never had crystallization problems, but then again I nearly always use the PO solution at room temperature.

    However, if I understand the issues as they are being stated, I conclude the following. Please correct me if I am wrong.

    1. Michael proposes using a weaker solution of potassium oxalate because this apparently gives better clearing in his condition. I am assuming he mixes the PO solution from well water rather than with distilled water?

    2.Ole suggests that problems in clearing may be due to the formation of calcium oxalate, and proposes as the solution ether filtering the PO solution, or mixing it with distilled water, noting that reducing the concentrate of the PO solution will not address this particular problem.

    3. Eric uses a concentrated solution of PO, and mixes with a reverse osmosis system, and apparently gets good clearing with this technique.

    In my own work I usually have no problem at all in getting good clearing, with PO solution mixed with tap water, but have noticed that from time to time a fresh mixture of PO would immediately result in some staining, even though all other conditions were the same. From this discussion I am beginning to suspect that the culprit for this may be seasonal changes in my tap water so I will plan to mix my PO solutions in the future with distilled water.

    Now, is there any literature which suggests that the clearing baths might also benefit from being mixed with distilled water.


    Sandy

    Sandy, I haven't seen it written other than in my book, but I trust my eyes. A cloudy bath indicates the formation of a solid. With distilled/RO water I have not seen the cloudy effects. The cloudiness will appear with HCL clearing bath as well as plain tap water; this was very evident when prints were made in Taos from wells. Potassium Oxalate has been made in my darkroom and those that I work in for the past 25+ years with ONLY distilled or RO water.

    Eric

  9. #29

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    Eric,

    Well, you have convinced me on this, and I plan to mix the PO solutions with distilled water from now on.

    What about the other question. Do you use tap distilled water (or reverse osmosis) for mixing the clearing baths?

    Sandy




    Quote Originally Posted by EricNeilsen
    Sandy, I haven't seen it written other than in my book, but I trust my eyes. A cloudy bath indicates the formation of a solid. With distilled/RO water I have not seen the cloudy effects. The cloudiness will appear with HCL clearing bath as well as plain tap water; this was very evident when prints were made in Taos from wells. Potassium Oxalate has been made in my darkroom and those that I work in for the past 25+ years with ONLY distilled or RO water.

    Eric

  10. #30
    EricNeilsen's Avatar
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    Sandy, Sorry, I was trying to get some digital work done an djust used APUG as a break. I also use the RO water for 95% of my clearing bath mixing. When I was on a well in Taos, every trip to the store included a hand full of distilled water. The RO system has been great in providing good clean water.

    I had two additional thoughts on the cystals that Mike was having problems with on his prints. Was that from the "hard to mix" developer? Perhaps you just didn't have your chemistry balanced and the solution that you beleived to be PO was indeed too heavy in Oxalic Acid? I have noticed over time of using it, that it has a tough time staying in solution (rather low soluability perhaps), and with the heated solution you are able to get it into solution, but after developing it, the print cools enough to allow the recrystalization of Oxalic acid?

    What if you soak it in some hot distilled water?

    What paper did this happen with?

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