Carbon Transfer printing times

Discussion in 'Alternative Processes' started by SMBooth, Mar 8, 2015.

  1. chrisaisenbrey

    chrisaisenbrey Member

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    Just to promote once again the less toxic alternative to dichromate:

    Tissue sensitized with DAS (4,4′-Diazido-2,2′-stilbenedisulfonic acid) is stable for a couple of weeks. However the DAS has to be added to the gelatin glop before coating.

    Chris
     
  2. Andrew O'Neill

    Andrew O'Neill Subscriber

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    Chris, how do you account for slight variations in negative DRs? I aim for a specific DR, but it's either slightly longer or shorter. I can remedy this by sensitizing the tissue for particular negative. How do you store your DAS tissues? Freezer?
     
  3. chrisaisenbrey

    chrisaisenbrey Member

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    Hello Andrew,

    The gamma of the DAS tissue can be adjusted by the amount of lamp black and by the amount of DAS. Like for dichromate less DAS gives higher gamma as with dichromate. (I’m using 100-200 mg of DAS and 125-250mg of lamp black for 5g of gelatin 225 Bloom at the moment)

    I’m actually printing two layers on top of each other:
    A low gamma layer with long exposure for the lights and a short exposure with high gamma for the shadows. I think this crates a kind of toe for the lights.

    I store the tissue simply at room temperature, once it is dry inside a book to keep is more flat.

    Chris
     
  4. Andrew O'Neill

    Andrew O'Neill Subscriber

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    That's very interesting, Chris. For your highlight layer, are you putting in considerably less pigment then? I'd love to hear more about your process. Thanks!
     
  5. CMB

    CMB Member

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    The shelf life of DAS sensitized carbon tissue, stored in “normal” temperature and humidity environments, is in excess of twenty-years. This I know because today I am making tricolor carbon prints with materials coated in 1994.


    With this in mind, it would seem that sensitizing carbon pigment films at a variety of DAS concentration levels (and then storing them away for when the appropriate negative comes along - like having boxes of grade 2, 3, 4 silver print papers) would achieve the need for carbon print materials of different gammas.

    Charles
     
  6. Andrew O'Neill

    Andrew O'Neill Subscriber

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    Thanks, Charles.
     
  7. Andrew O'Neill

    Andrew O'Neill Subscriber

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    @chrisaisenbrey Old thread but where do you get your DAS from? Thank you.
     
  8. chrisaisenbrey

    chrisaisenbrey Member

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    I got one batch of DAS from a one time group purchase from the member holmburgers. The newer batch I got from the French supplier “phototypie”. Unfortunately they seem to be out of stock at the moment:

    Dead Link Removed
     
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