Fine crystals on palladium prints

Discussion in 'Alternative Processes' started by mikepry, Feb 5, 2006.

  1. mikepry

    mikepry Subscriber

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    Well the darkroom demons have come back again this month. After mixing fresh potassium oxalate I am noticing really small and fine sparkly crystals on my dried prints. If we were back in the 70's it wouldn't be a problem but now it is! The new PO is the only "new" thing in my process. It is at 33%. I recall seeing this posted before and for the life of me I can't find the thread after numerous attemps. Could someone enlighten me as to what could be causing this? BTW my 15 yr old daughter was looking at my latest prints and she remarked....."Cool, these sparkle in the light." Thanks in advance.
     
  2. photomc

    photomc Member

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    Hi Mike...don't know if this is the thread you were looking for, but it might help. That's about as much help as I could be with this, hopefully the guys that know will post something. Please, do post what you find as the reason.
     
  3. Michael Mutmansky

    Michael Mutmansky Member

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    Mike,

    33% is close to saturation, but that should not really be an issue because the prints must go through all the clearing and washing steps after that, and PO is fairly readily soluble. The problem with being that high is that you will get crystals in the solution, especially if you use it warm or hot. This can cause damage to the print surface as you pour it over the print, etc.

    I've never had crystalization problems on my prints, so I don't know where to start to solve the problem, but you may want to look at the steps nearest to the end; the wash and the clearing steps. Are you positive you washed long enough? What clearing baths did you use? If you put the print back in water, does the crystals clear, or do they remain?

    Most everyting that we use is fairly soluble in H2O, so my initial thinking is that you may be able to salvage the prints by washing longer. If I had to guess, I would also go with not enough washing after the clearing bath is resulting in some remaining clearing bath chemicals in the paper at the most likely candidate.


    ---Michael
     
  4. EricNeilsen

    EricNeilsen Member

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    Mike, Are you making your own or mixing from powder? Where did yo buy your powder? What clearing baths do you use?

    Eric
     
  5. Ole

    Ole Moderator Staff Member

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    Just a quick thought: Is your tap water hard, and do you use tap water at any stage in the process? Those small crystals could be calcium oxalate, which will be very difficult to wash off!
     
  6. Michael Mutmansky

    Michael Mutmansky Member

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    Ole,

    By what mechanism does the calicum in hard water react and produce calcium oxalate?

    I'm on hard (but not really hard) water, and haven't noticed any crystalization with PO, but maybe the calcium is in low enough concentration to not cause the problem.


    ---Michael
     
  7. Ole

    Ole Moderator Staff Member

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    Any calcium in the water will form calcium oxalate. Calcium oxalate is insoluble, and will sho up as small white crystals. Incidentally, that's what kidney stones are made of.
     
  8. Michael Mutmansky

    Michael Mutmansky Member

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    Ole,

    Does it strip off the potassium, or does it need free oxalic acid to form?

    Do you know if any of the clearing bath solutions are better at removing this if it forms?


    ---Michael
     
  9. Ole

    Ole Moderator Staff Member

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    Michael -

    potassium oxalate in solution consists of potassium ions and oxalate ions. The oxalate will combine with any calcium ions to form insoluble calcium oxalate monohydrate.

    There's no "stripping" going on - that's already done when you make the solution.

    You won't manage to dissolve it, the only cure is prevention: Add a little potassium oxalate to the water, let stand for a day, then filter before use. Or use distilled / deionised water.
     
  10. BrianShaw

    BrianShaw Member

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    biological analogy

    Hi,

    I'm a kidney stone expert (not on the MD side, incidently). According to my urologist, oxalic acid is required to precipitate the most common kidney stone... calcium oxalate. Without the oxalic acid the doctor claims the calcium passes freely in the "wash". That's why one of the standard preventative treatments is avoidance of oxalic-bearing food, like spinach and other healthy leafy green veg, cola drinks, coffee, etc. and plenty of water/beer. I know that there is also a chemical preventative treatment but I can't remember what it was. Once the Doc prescribed this (two large horse pills per day) but I stopped taking them -- they passed whole and it was weirding me out! Allegedly whatever chem this was would bind with the calcium and take it out of the system.

    I hope there is a chemist in the house that can continue to help chemically explain your phenomenon. But, it does kinda' sound cool... if the sparkles are in the right place.
     
  11. Michael Mutmansky

    Michael Mutmansky Member

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    Ole,

    Right, of course, I wasn't thinking about the PO in ionic form in solution.

    That must mean that I don't have too much calcium in my water (even though it is city water from limestone spring/well sources, and is considered 'hard' by many people), as I don't see the problem in the prints at all.

    However, if it is not soluble, how would it form crystals on the surface of the print? That would imply that it was in solution before the paper dried, correct?

    It seems that the formation of the calcium oxalate might be in the first rinse or clearing bath after the PO, because any traces of free oxalates will disappear fairly quickly unless Mike is using oxalic acid as a clearing bath acid.

    Any chance EDTA might bind up the calcium so it cannot react with the oxalates? I believe that is the mechanism it uses with a variety of metals (in particular copper and iron).


    ---Michael
     
  12. EricNeilsen

    EricNeilsen Member

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    If you are getting a precipitate on your prints, You should try mixing your first clearing bath with distilled water and go directly into it from your developer. Does your clearing bath look milky or clear? (Not colorless but Clear) If you are getting solids in your first clearing bath, you should try an alternative clearing process.

    Eric
     
  13. Michael Mutmansky

    Michael Mutmansky Member

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    Ole,

    Thinking about it, I am getting some calcium oxalate, but it is in the form of a precipitate in the water wash after the developer (that is cloudy after a print or so, I normally use a fresh water bath for each print).

    However, I'm thinking that the calcium oxalate does not have the tendency to form structures large enough to be visibly crystal forms unless there is an extremely large amount of calcium in the wash water, because it appears to precipitate rapidly before it has the chance to collect into larger structures.

    I'm thinking that it is a good suggestion for Mike to explore with some distilled H2O in the first bath, but it doesn't seem that it is the most likely candidate for the crystal problem.

    It might also help if he reduces the PO concentration down to 20-25%, as that would also reduce the possibility if the oxalates are indeed forming a crystalline calcium oxalate.


    ---Michael
     
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  15. Ole

    Ole Moderator Staff Member

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    Oddly enough, the less calcium there is the larger crystals will tend to form. With lots of calcium it will just go milky with lots of microscopic grains...

    "Insoluble" is a relative term. Calcium oxalate is relatively insoluble, but still soluble enough that crystal growth will occur with low calcium concentration. Reducing the oxalate concentration enough to matter is not a viable proposition, you would have to go down to a few ppm to make any difference! It is much easier to eliminate the calcium.
     
  16. EricNeilsen

    EricNeilsen Member

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    There is no reason to dilute the developer to avoid the problem. He simply needs to avoid either a plain water rinse or use only distilled water. I use a reverse osmosis system and use it to rinse my prints after the developer and before the first clearing bath.
     
  17. Michael Mutmansky

    Michael Mutmansky Member

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    Eric,

    You missed my point, which was that a lower concentration PO solution will clear more quickly out of the paper, and will make it possible to possible get a fairly complete clearing of the PO in a single wash bath before moving to clearing baths. The less PO left, the less oxalate to react with any calcium in the clearing baths.

    It's also a good reason to encourage the physical removal of the PO by dumping; something that may not be stressed enough in the normal texts.


    ---Michael
     
  18. mikepry

    mikepry Subscriber

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    Well the problem was that my developer was too hot(110). I confirmed this yesterday evening. With the new developer this started happening. When I backed down to about 90 degrees it stopped. I was trying to make my own PO and it ended up in a mess. I am no chemist. Thought I could save some bucks but ended up throwing good money away for bad. I'll not do that again. I was happy to find out that Mike at Artcraft will really discount the price when you buy five or more pounds of the powdered PO. That was good news. Everything is working fine now with lowering the developer temp. 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!!!!
     
  19. EricNeilsen

    EricNeilsen Member

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    Michael, What do you mean " by dumping". I am not familar with that expression as used here. Do you mean, pouring off? I use a single tray method most of the time. So it all gets dumped off before clearing begins.
     
  20. EricNeilsen

    EricNeilsen Member

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    Mike, It is really easy to make it yourself. 2 lbs of Potassium Carbonate, 1.75 lbs of Oxalic Acid and some water. Add the Potassium Carb to 1/2 gal of water and stir. Then , slowly add the oxalic acid in a well ventilated space, and you should end up with a about a gallon after you top it up. Did it bubble up to fast? I use a 3 gallon container when I mix a gallon. Keeps it all inside the bucket.

    Lights can vary in their output. If you have another wattage device on the circut, you may want to rearrange the plugs to better distribute the load. Poor grounding can also look like a voltage drop and cause your lights to flicker.

    Eric
     
  21. sanking

    sanking Restricted Access

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    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


     
  22. sanking

    sanking Restricted Access

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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




     
  23. clay

    clay Subscriber

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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.
     
  24. mikepry

    mikepry Subscriber

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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!
     
  25. Michael Mutmansky

    Michael Mutmansky Member

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    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.
     
  26. Michael Mutmansky

    Michael Mutmansky Member

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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