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  1. #11
    John_Brewer's Avatar
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    Quote Originally Posted by Ole
    Instead of dichromate, I have found that a drop of 6% hydrogen peroxide is a nice and safe(ish) highlight restrainer.
    Actually hydrogen peroxide appears to give an increase in contrast. What it is doing is rapidly oxidising the print. The same colour will be achieved over time (sometimes days) as it is exposed to oxygen in the air.
    ~John~
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    There are 10 types of people in this world - those who understand binary and those who don't.

  2. #12
    Ole
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    John, you misunderstand: I didn't mean that I add the H2O2 in the wash, I add it in the emulsion! Then it restrains highlights by ensuring the oxidation state of unexposed aread.
    -- Ole Tjugen, Luddite Elitist
    Norway

  3. #13
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    Oh, thanks for clarifying that Ole. What strength and quantity H2O2 do you use?

    J
    ~John~
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    There are 10 types of people in this world - those who understand binary and those who don't.

  4. #14
    nze
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    Hi

    in fact any contrasting agent may be use. Dichromate (potassium or ammonium), potassium Chlorate work well so does Potassium alun. I use all of them with goof result and now I only use dichromate as I got a big box of it.

    you may read these 2 artciles by Mike Ware ( Who wrote a book on Cyanotype)
    http://www.mikeware.co.uk/mikeware/A...e_Process.html
    http://www.mikeware.co.uk/mikeware/N...e_Process.html
    http://www.amazon.com/exec/obidos/tg...books&n=507846
    Chris Nze
    me Apug Portfolio
    Me web page

  5. #15
    John_Brewer's Avatar
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    Thanks Christian. I particularly like the idea of Ole's suggestion of H2O2 as a highlight restrainer - cheap as chips from any pharmacy- and thus saving dichromate for gum printing
    ~John~
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    www.johnbrewerphotography.com
    There are 10 types of people in this world - those who understand binary and those who don't.

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