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Thread: Potassium Dichromate on Mahogany Cameras

  1. #21

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    Re: Potassium Dichromate on Mahogany Cameras

    Leather shoes not treated with Dichromate may be difficult to find... so final product may not be hazardous if precautions used to change oxidation state of remaining Chromium.

    But working with Dichromate can be very hazardous, and it's better to avoid it.

  2. #22
    Mark Sawyer's Avatar
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    Re: Potassium Dichromate on Mahogany Cameras

    I'm going to try it (carefully) on a few mahogany scraps, and perhaps a lens box or two, and compare it to more conventional stains (which win no safety prizes either).
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

  3. #23

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    Re: Potassium Dichromate on Mahogany Cameras

    Quote Originally Posted by Mark Sawyer View Post
    I'm going to try it (carefully) on a few mahogany scraps, and perhaps a lens box or two, and compare it to more conventional stains (which win no safety prizes either).
    One tip. By mixing a Dichromate solution (orange colored) with used BW developer it hapens that chromium changes the oxidation state to a way safer stuff, it changes color from orange to dark green. I've been using this tip to lower Dichromate toxicity after finishing job, when using it as bleach for BW reversal. So I suggest to use that, or equivalent process.

    "By mixing it with used developer" ... "The orange chomium(VI) is reduced to the green chromium(III) which is much less toxic and harmful to the environment and is no longer carcinogenic."

    https://www.photrio.com/forum/index....essing.101014/

    You also can "clean" tools, gloves, etc with a chemical that reduces the VI to the safer state.

  4. #24

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    Re: Potassium Dichromate on Mahogany Cameras

    Quote Originally Posted by Pere Casals View Post
    One tip. By mixing a Dichromate solution (orange colored) with used BW developer it hapens that chromium changes the oxidation state to a way safer stuff, it changes color from orange to dark green. I've been using this tip to lower Dichromate toxicity after finishing job, when using it as bleach for BW reversal. So I suggest to use that, or equivalent process.

    "By mixing it with used developer" ... "The orange chomium(VI) is reduced to the green chromium(III) which is much less toxic and harmful to the environment and is no longer carcinogenic."

    https://www.photrio.com/forum/index....essing.101014/

    You also can "clean" tools, gloves, etc with a chemical that reduces the VI to the safer state.
    This advice seems a little risky to me. Mostly because you aren't specifying which developer you are mixing with. It's unlikely that mixing used Pyro developer would have the same results as mixing it with used D-76 for instance (it could even be disastrous). You can reduce Hexavalent chromium to the safer CrIII using Asboric Acid. That is probably the safer approach and is documented in a scientific research paper.

  5. #25

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    Re: Potassium Dichromate on Mahogany Cameras

    Quote Originally Posted by domaz View Post
    This advice seems a little risky to me. Mostly because you aren't specifying which developer you are mixing with. It's unlikely that mixing used Pyro developer would have the same results as mixing it with used D-76 for instance (it could even be disastrous). You can reduce Hexavalent chromium to the safer CrIII using Asboric Acid. That is probably the safer approach and is documented in a scientific research paper.

    You are right, a list of safe developers should be added...

    Xtol contains ascorbic acid as main developer. I've used that tip with Xtol and D-76 with good results.

    I would not mix dichromate with Pyro without knowing safety...

    It is true that mixing Dichromate with used developer has been a common practice in reversal process with Xtol, D-76, Dektol (also Vit C there) and Ilford PQ universal. This has been done extensively in cinematoghraphy, reversing Tri-x, Double-X , etc it has been common in the past, often with Dichromate bleach. But as you suggest, mixing chemicals can be hazardous, so before mixing a developer with Dichromate one must know that it can be done with involved developer, you are right. Goog to know that Ascorbic Ac is a good way...

    In fact what I wanted to point is that Dichromate should be reduced to CrIII as soon as possible after usage, including drops remaining in glassware, gloves, etc

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