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  1. #1

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    Maintaining Potassium Oxalate Developer Solution Over Time

    I recently purchased and have been reading Dick Arrantz's book on Pl and Pt Printing (2nd Ed.).

    In this book, he states that developer is never discarded, that the age of his developer is 20 years. He recommends adding water when crystallization starts to appear.

    While I find this interesting for an archival process, I like the environental implications. But versus watching for crystalization, what's a better way to monitor the health of this bath? For example, could one monitor pH and add water when the pH extends beyond predefined limits? Or, perhaps one could monitor density and add water when it goes out of range?

    And, what about buffers or contaminates from countless sheets of paper entering this bath over time? Can their accumulation have negative consequences? I imagine such a bath eventually reaches some sort of equilibrium.

  2. #2

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    Bear in mind that each time you develop a print some of the developer is used up so in practice one must constanly add back to the main solution to top it off. I add back about 50ml of new solution for every 80-100 square inches of print development. So if you doing a lot of printing you will have replaced the entire contents of a liter of devleoper through topping it off.

    Secondly, it is important to monitor the pH of the developer to make sure it stays acidic. As you run paper through the developer, especially papers that are a bit alkaline, the solution may become more base unless you take steps to counter it. I add oxalic acid to the solution to keep the pH at around 6.0.

    From time to time I filter the solution.

    That is about it.

    Sandy

    Quote Originally Posted by Neil Poulsen
    I recently purchased and have been reading Dick Arrantz's book on Pl and Pt Printing (2nd Ed.).

    In this book, he states that developer is never discarded, that the age of his developer is 20 years. He recommends adding water when crystallization starts to appear.

    While I find this interesting for an archival process, I like the environental implications. But versus watching for crystalization, what's a better way to monitor the health of this bath? For example, could one monitor pH and add water when the pH extends beyond predefined limits? Or, perhaps one could monitor density and add water when it goes out of range? Or both? When does one know to add more potassium oxalate?

    And, what about buffers or contaminates from countless sheets of paper entering this bath over time? Can their accumulation have negative consequences? I imagine such a bath eventually reaches some sort of equilibrium.
    Last edited by sanking; 01-22-2006 at 02:43 PM. Click to view previous post history.

  3. #3

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    Neil,

    There are very few things that Dick had in either book that are incorrect. This is one that is true; the PO will be functional as long as it is not destroyed or lost. However, I disagree with Dick on this for a variety of reasons, not the least of which is the contaminants that you mention (which is quite considerable, especially if the developer is used warm or hot).

    Plus, you ultimately do not know what the FO pt and/or pd salts, restrainers, and other hangers-on will do to your image. What I mean is, develop one in fresh developer, and then develop one in aged developer and you will probably see a difference. Can you quantify the difference? No. You only really know that the fres PO is fresh, and that is a somewhat repeatable starting point for future printing.

    This is especially a problem if you use the dichromate method of contrast control, as I believe the dichromate becomes consumed somewhat, by the development, or possibly the buffers react with it, causing the contrast to drift a bit with continued use.

    PO is not expensive if you mix it yourself, and it is not an environmentally harmful chemical that I'm aware of, so it makes sense to me to be more agressive about replenishment of the developer. It should help produce more consistant results in the long run.

    The most important concern for maintaining the developer is the pH. There was a discussion about that recently here, but generally most people aim for about ph of 5 to 6. As the pH climbs, it becomes less effective as an initial clearing bath. As it crosses over to the basic side, it will actually hinder clearing by converting the FO into a less soluble version.

    I us pH strips from Edmunds (100 strips for $1.00) to test. If it is above 6, I add a little oxalic acid to drop it down a bit.


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

  4. #4

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    would like to add one more question to Neils excellent post....what is meant by "topping off" ? Do you add x amount of water, water + PO? Sorry, this is probably clear to everyone but me...I understand if you made up 1 liter of PO, after a period of use, it could be reduced down to say 950 ml, would you then add water back to equal 1 liter, or would you add 50 ml of water + x grams of PO?

    TIA
    Mike C

    Rambles

  5. #5
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    Another thing to think about is that as you print allot your developer will disapear. A dry peice of paper goes in the developer and then transfers to the clearing bath wet; you will lose some of your developer with each sheet. So replenishing is automatic by necessity. I don't use Dichromate and simply top off what I lose and the PH of my PO stays acidic. The PH strips are really good to have around.
    "If I only had a brain"-Some badly dressed guy made of straw in some movie I think I saw

  6. #6
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    Mike,

    The PO is pretty much a saturated solution at I think around 33%. If you lose 100ml just measure 33gm, mix it to make 100ml and add away. My method is allot more low tech and it works. If you use your developer real hot you'll be dealing with crystals all the time and figure out that the percentage of PO will almost automatically stay above the saturation point.
    "If I only had a brain"-Some badly dressed guy made of straw in some movie I think I saw

  7. #7

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    As indicated, I top off by adding back to the developer about 50ml of fresh solution for every 100 square inches of print development. I use dichromate control and add back the dichromate in the fresh solution in the same ratio as it is found in the main solution. For example, if the main solution contains 2ml of a 5% potassium dichromate solution per liter of solution, when I top it off with 100 ml of fresh solution I also add four drops potassum dichromate (where twenty drops = 1 ml).

    Sandy



    Quote Originally Posted by photomc
    would like to add one more question to Neils excellent post....what is meant by "topping off" ? Do you add x amount of water, water + PO? Sorry, this is probably clear to everyone but me...I understand if you made up 1 liter of PO, after a period of use, it could be reduced down to say 950 ml, would you then add water back to equal 1 liter, or would you add 50 ml of water + x grams of PO?

    TIA

  8. #8

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    Thanks Mateo and Sandy....that is Exactly what I needed.
    Mike C

    Rambles

  9. #9

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    Contrast Agent

    Out the starting gate, I purchased potassium chlorate from P.F. for my contrast agent. Does this have the same affect on the developer as the potassium dichromate?

    Sandy, I just saw your second response. I'm not quite following when you say,

    "I use dichromate control and add back the dichromate in the fresh solution in the same ratio as it is found in the main solution."

    Is the "main solution" to which you refer the coating solution or the developer solution? My understanding is that potasium dichromate enters the developer through the print coating.

    I like the idea of not tossing developing chemistry, just adding to it. I'm wondering about having a bottle of developer available for each paper so as to minimize the effect of one paper on the development of another, to avoid cross-contamination.

  10. #10

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    Neil,

    I use the dichromate in the developer, not in the coating solution. What I am trying to convey is that I replenish the main solutin of developer with fresh solution that contains proprotially the same amount of dichromate.

    Sandy

    Quote Originally Posted by Neil Poulsen
    Out the starting gate, I purchased potassium chlorate from P.F. for my contrast agent. Does this have the same affect on the developer as the potassium dichromate?

    Sandy, I just saw your second response. I'm not quite following when you say,

    "I use dichromate control and add back the dichromate in the fresh solution in the same ratio as it is found in the main solution."

    Is the "main solution" to which you refer the coating solution or the developer solution? My understanding is that potasium dichromate enters the developer through the print coating.

    I like the idea of not tossing developing chemistry, just adding to it. I'm wondering about having a bottle of developer available for each paper so as to minimize the effect of one paper on the development of another, to avoid cross-contamination.

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