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Thread: Pyrocat-HD

  1. #1
    Jimbob's Avatar
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    I having trouble mixing the "B" solution. I keep ending up with what appears to be an unmixed solution. I talked with the Photographers Formulary and was given advice about mixing the Potassium Carbonate to quickly. So I tried another batch mixing it much slower. However, I ended up with a milky looking stock solution. When it sits for a while it separates. I've tried mixing at both 68 degrees and 100 degrees. Same result. Can anyone help?

    Thanks
    JIMBOB

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    Sometimes it's hard to mix. Are you using distilled water - that may help. I use sodium carbonate, and it's even harder to mix with water. I mix it in 5 times the amount of water, then, when mixing the working solution, add five times as much. That gets the right amount of chemical into the solution, and the added water is not enough to worry about.

    With potassium carbonate, you might want to try doubling the amount of water for the stock solution. Then, if you are using the working solution 1:1:100, you'd actually use 1:2:100.
    juan

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    you can still use the solution if you stir it up before adding to the water for the working solution. going forward, you should addthe potassium carbonate VERY slowly into the 100ml of water, taking care to disolve it a little bit at a time.

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    L Gebhardt's Avatar
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    I had the same problem. I beleive the dirrections say to add it to 100ml of water, not add water to make 100ml. I think I added about 30ml more water and it desolved. I am still confused by the directions, and I think I will mix it from scratch next time.

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    You should try using triethanolamine in place of the Kodalk or metaborate solution. Triethanolamine (TEA) is available from Photographer's Formulary or www.chemistrystore.com. Use the same amount of it as you do PMK A solution. That is, for example, 10 ml A + 10 ml TEA + 1000 ml water.

    This avoids all the hassle of mixing metaborate and the uncertainty of exactly what Kodalk is. TEA is an organic base that becomes basic when you add it to water.
    Gadget Gainer

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    Whoops! I am getting too old. What I said about TEA applies to PMK. TEA may not be alkaline enough for Pyrocat-HD.

    The cloudy carbonate solution may be due to hard water, which contains calcium and/or magnesium. Their carbonates are insoluble and form the cloudy solution you described. Tetrasodium EDTA may cure it, but it's cheaper just to use distilled or demineralized water unless you have on hand the EDTA.
    Gadget Gainer

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    Quite a number of folks have reported difficulty in mixing the B solution of Pyrocat-HD with the Formulary kit. Since I have never used this kit I don't actually know either exactly what is in there, nor the directions for mixing. Perhaps if you could send me a description of how the kit is packaged, and the directions for mixing, I could figure out the problem.

    I have always mixed Pyrocat-HD from bulk chemicals and not from a kit, and when the potassium carbonate is added slowly to the water, as described in the article at www.unblinkingeye.com, I have never had a problem with getting the chemical into solution. And there should not be either, since potassium carbonate is soluble in water in percent solutions well over 120%, and one is nowhere near this figure when adding 100g of chemical to 100ml of water.

    One of the mistakes that a number of people have made in the past is to attempt to mix the 100g of chemical in water to make 100ml of solution, but as someone points out further in this thread, the correct way to mix is to add 100g of chemical *slowly*, and with constant stirring, to 100ml of water, which will give a final total solution of around 125-35ml of B stock solution. Since slowly is a relative term I will qualify it for this context by saying that it should take no longer than about two minutes add the potassium carbonate to the water and have it completely in solution. And contrary to some recommendations I have seen, water at room temperature (70F or greater) has always worked fine for me.

  8. #8
    gainer's Avatar
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    I mixed 350 grams of Potassium carbonate with 350 ml water to get 500 ml of solution with no problem, but I have hard well water, so I used either rain water or distlled water from the store, I don't remember which. When I dissolve any carbonate in my well water, I get the cloudy solution which eventually precipitates the calcium-magnesium carbonate.
    Gadget Gainer

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    Success! Thanks to all for your help. One thing I really appreciate about photographers is there willingness to share information.

    I found by adding the Potassium Carbonate to 200 ml of distilled water it cleared up almost immediately. I'll just work with the 1:2:100 dilution. I've experienced few problems with mixing chemicals. The kit may the culprit.

    Anyway, thanks again!
    Regards,

    Jimbob

  10. #10
    roy
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    [quote="Jimbob"] One thing I really appreciate about photographers is there willingness to share information.

    Something this forum possesses in abundance.
    Roy Groombridge.

    Cogito, ergo sum.
    (Descartes)

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