Double Printing Cyanotypes

Discussion in 'Alternative Processes' started by Robert Ley, Jan 10, 2018.

  1. Robert Ley

    Robert Ley Subscriber
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    I have some cyanotypes that are too light and would like to over print with cyanotype. My initial thoughts are that the cyanotype emulsion which contains potassium ferricyanide might bleach the previous image. I plan to overprint these with VDB. Any help that you could give me on either procedures would be appreciated.
     
  2. Bob Carnie

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    A lot of People do Gum Pigment over Cyanotype with amazing results.
     
  3. nmp

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    You are thinking of potassium ferricyanide bleaching a silver image. No silver here.
     
  4. jim10219

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    Yeah, cyanotype over cyanotype should be fine, assuming you can get the registration right. Coating might be an issue as the cyanotype emulsion is really thin.

    Did you know you can splash some hydrogen peroxide on it to darken the image? You have to do this right after initial wash. Once it dries, it doesn’t work as well. Cyanotype s naturally darken over time as they are exposed to oxygen. The hydrogen peroxide just speeds up that process.

    Good luck printing Van Dyke over it. They usually don’t go well together, unless you’re looking for funky bleached spots, or mask out the overlapping areas so the emulsions don’t touch.
     
  5. sly

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  6. OP
    OP
    Robert Ley

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    Thanks for all the replies. Registration won't be a problem as the prints have been three hole punched I already have two registered negatives. I am going to try the VDB over cyano and if doesn't work the way I would like I will try gum over. I will let all know how it works, but it may be a while as I am going into hospital for a total knee replacement.
     
  7. NedL

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    pdeeh tried it a while ago. Sounds like you might want to overprint the cyanotype and hit it with H2O2 before the VDB layer.
    Or maybe coat your finished cyanotype with some diluted PVA size and let it dry before applying the VDB.
     
  8. nmp

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    Forgot about that thread. Do we have understanding of why cyanotype layer fades when processing VDB topcoat?
    (haven't seen pdeeh for a while around here.)

    :Niranjan.
     
  9. NedL

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    IDK but sometime I might try your KBr idea... just to see what happens.
     
  10. Herzeleid

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    I have tried VDB over Cyanotype and vice versa few times. Registration is the simplest of problems.
    If an alkaline fixer is used it will bleach cyanotype layer, if an acid fix is used it is harsh for VDB layer. More neutral fixer will slowly bleach cyanotype, and it eats away the highlights of silver image.

    I helped a friend for a chemical reaction video and we used some ferric salt (any ferric salt will do the same) and sodium thiosulfate. You start with a dark red iron solution and it becomes clear gradually when you add thiosulfate.
    Sodium thiosulfate reacts with iron salts that is why cyanotype layer weakens/fades after it goes into fixer.
     
  11. nmp

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    Thanks, Serdar. So it is during fixing that this fading occurs. It makes all the sense. Sodium thiosulfate is a strong reducing agent. It will readily reduce Prussian Blue of the cyanotype to Prussian White, as per item I of this article:

    http://pubs.acs.org/doi/abs/10.1021/ed020p198.1?journalCode=jceda8

    Prussian white is supposedly unstable in air and should oxidize back to the blue form. Perhaps this air re-oxidation is hindered somewhat because of the VDB layer on top. In that case, using an oxidizing agent like hydrogen peroxide might help.

    (Great, more experiments!)

    :Niranjan.
     
  12. nmp

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    Glad someone could fall for one of my crazy ideas....:D
     
  13. Herzeleid

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    Niranjan,

    It is good to know the reduction end product, you are right it might be oxidized back to prussian blue. If it is not water soluble, I fear some iron might be removed from the paper.
    It has to be tested as you said. May be more is happening in sodium thiosulfate.

    If you look at youtube for ferric salts and sodium thiosulfate reactions, you will see the resulting solution is colorless and clear. For example I made the reaction for video with ferric sulfamate, it is dark orange/red colored, ferrous sulfamate is bright green colored. End product in thiosulfate solution is water clear. IMO, more is going on then just reduction.

    Ferric nitrate reduction in sodium thiosulfate


    Regards
     
  14. nmp

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    Thanks for sharing the video. Nice bird chirping background music....:smile:

    Indeed, nothing is ever simple. For example in case of cupric sulfate + Na thiosulfate, the reaction pathway seems to be affected by the relative ratio of the two.

    http://www.crscientific.com/article-redox3.html

    (sorry, OP. I guess you didn't bargain for all these chemistry stuff...)

    :Niranjan.
     
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