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  1. #1

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    Potassium Dichromate - a couple of questions (UK)

    Hi,

    For a number of reasons I have been away from alternative printing for a couple of years and am now in a position to start printing again. However I notice that potassium dichromate (I use it for contrast control in the kalitype process) is not readily available to individuals in the UK and although I have a small amount of chemistry remaining I was wondering whether any one could possible help with a couple of questions I have:

    1. Can you substitute sodium dichromate for potassium and if so is it obtainable in the UK?
    2. What is the shelf life of 5% potassium dichromate solution? (I have about 80ml made up which is I guess about 3 years old).

    I'm guessing this has caused a few problems to other UK alt printers and wonder how this lack of availability of potassium dichromate has been over come?

    Thank you

    John

  2. #2
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    Hi John

    Sorry can't help with your first question.
    I have been using a 5% solution of potassium dichromate in my sodium citrate developer and was wondering about shelf life myself (as mine is at least 5 years old). I found this information on dpug from Sandy King:

    "I agree that ammonium and potassium dichromate solutions last virtually forever. But this is absolutely true only if you mix with distilled water as tap water may contain impurities that will make the solution go bad in a very short time. I store my dichromate solutions in clear glass bottles in the dark and I have never had a solution go bad that was mixed in distilled water."

    I'm not sure what is looks like when it's gone bad? Mine has a small white blob floating in it? The solution still seem to work though.

    david

  3. #3

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    Quote Originally Posted by UKJohn View Post
    Hi,

    1. Can you substitute sodium dichromate for potassium and if so is it obtainable in the UK?

    John
    It's the dichromate part that makes both substances highly toxic, carcinogenic, flammable and a mutagen,
    so it would surprise me if one substance was outlawed and the other freely obtainable.

  4. #4
    Jim Noel's Avatar
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    Try hydrogen peroxide in your sensitizing solution. It works for me. The down side is that it is sold in plastic bottles and releases the extra oxygen atom through osmosis. I solve that by storing in totally full small brown glass bottles.
    [FONT=Comic Sans MS]Films NOT Dead - Just getting fixed![/FONT]

  5. #5
    mr rusty's Avatar
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    If you need some, you will find some suppliers on that well known auction site. Now I know and you know it is totally against the regulations to send this stuff through the post, but.......

  6. #6
    Hexavalent's Avatar
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    Quote Originally Posted by mnemosyne View Post
    It's the dichromate part that makes both substances highly toxic, carcinogenic, flammable and a mutagen,
    so it would surprise me if one substance was outlawed and the other freely obtainable.
    Neither the sodium or potassium salts are flammable. Ammonium dichromate is however flammable and therefore sometime has further availability/shipping issues.
    Last edited by Hexavalent; 12-01-2013 at 10:03 AM. Click to view previous post history.
    - Ian

  7. #7

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    Hi Jim,

    Thanks for the reply. Do you use the hydrogen peroxide undiluted or do you make it up into solutions?

    Thanks John

  8. #8

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    Hi Davido,

    That's really helpful thanks. I do use distilled water so fingers crossed all will be fine with the solutions I have.

    John

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  10. #10

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    http://www.amazon.co.uk/AC-PRODUCTS-.../dp/B004GAWDR8

    No connection, seems "regulations" don't apply to everyone.
    http://www.flickr.com/photos/red_eyes_man/

    Photographer not a job description - a diagnosis.

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