Iodine + B&W Prints ... Interesting

Discussion in 'B&W: Film, Paper, Chemistry' started by htmlguru4242, Aug 28, 2005.

  1. htmlguru4242

    htmlguru4242 Member

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    I was reading about bleaching prints with tincture iodine, so I tried it with some old prints that I had hanging around. A 2% iodine tincture bleachies the prints to white within about 30 seconds. Then, just to see what would happen, I put them in developer, and, to my surprise, the original image re-developed in a delightful, thick brown color.

    Does anyone know why this is??
     
  2. Donald Qualls

    Donald Qualls Member

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    The elemental iodine (in solution in the alcohol of the tincture) reacts with the silver that forms the image and produces silver iodide, a light sensitive halide compound. Since you're doing this in the light, the halide is immediately reexposed, and when you develop, you get the image back (and since the print was previously exposed with an image, developed, and fixed, there's only enough silver present to recreate the original image density) -- the color shift is because silver iodide produced by bleaching gives a different silver grain size from the original (typically a chloride/bromide mixture, mostly bromide in modern materials), and silver grain size controls the warmth or coolness of print tone.

    It might be interesting to do the bleaching under safelight, apply a suitable clearing bath to remove excess halide, dry in darkness, and then reexpose the paper with a projected negative image, in effect blending the two images. The idodide would typically be faster than the bromide in most printing papers (though perhaps not as fast as papers that include developer in the emulsion), though it would be difficult to impossible to control contrast. You could also fully fog, develop, bleach, clear and dry to produce iodide paper without a preimpressed image (starting with RC paper, this could even be reasonably inexpensive). There'd still be no control of contrast, but it might be of interest for things like in-camera negatives, since it should be faster than common paper emulsions.

    Do be aware, however, that iodide places a great load on your fixer; only rapid fixer should be used, and this 100% iodide material will greatly reduce the capacity of the fixer. Iodide is also a restrainer in developing, and a 100% iodide paper might require using a pretty strong developer one-shot to get consistent results.
     
  3. Jordan

    Jordan Member

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    The tincture of iodine (which I believe contains iodine and potassium iodide) oxidized the silver in the print up to silver iodide, AgI. When you re-developed, you were reducing the exposed silver iodide back to silver. The brown colour probably results from changes in the crystal form on going from Ag to AgI and back to Ag.
     
  4. htmlguru4242

    htmlguru4242 Member

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    Excellent, I though that what was happening was something along those lines ... I'll try the fog / dev / bleach idea with some paper and see how it goes... (I'll have to cut the paper small though, as the largest format i have is 6x9cm 120. Do you thik the paper would be fast enough for pinhole photography?
     
  5. dancqu

    dancqu Member

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    Do you keep light levels low while doing that?
    Have you tested various strength solutions?

    If you've any sulfide try a .1% solution rather than
    the usual developer. Also, try the sulfide dip after the
    usual redevelopment.

    How about this: Totally expose a whole sheet of paper,
    develop, convert to iodide, then make a print. May be
    a good way to make home made AZO or any mix of
    halides paper. Anyone doing that? Dan
     
  6. htmlguru4242

    htmlguru4242 Member

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    I may just be being a little dumb here, but what do you mean by "sulfide"? Also, I am trying to make iodide paper and expose / develop it. I'm expecting some neat results. I'll certainly post with them once I get it o work.
     
  7. titrisol

    titrisol Member

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    Iodine tincture bleahes paper quite fast, and can imprint a green, brown or purple cast depending on how you redevelop.

    You can also use it on sleenium tined prints.... a very very cool effect.
    Bleach the selenium toned prints, rinse them and put them in fixer (plain hypo is fine)
     
  8. htmlguru4242

    htmlguru4242 Member

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    How would you go about getting a different color upon redevelopment?
     
  9. titrisol

    titrisol Member

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    I think there are a couple of articles on these in PhotoTechniques magazine and in the recipes section of APUG

    IIRC using cold tone developer will yield olive color, warmtone developer = lighter olive, sulfide = brown, etc etc.
     
  10. psvensson

    psvensson Member

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    He means sulfide toner. The two common commercial variants would be Kodak Brown Toner and Agfa Viradon.
     
  11. dancqu

    dancqu Member

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    Well, if you've iodine and potassium iodide for making
    that tincture I thought you might also have some
    sodium sulfide.

    In the usual bleach and redevelop process sodium
    sulfide is used. Why bother to buy a brand name
    SODIUM SULFIDE. That would be the same as
    buying a brand name SODIUM METABORATE.

    Brand name SODIUM TETRABORAT and SODIUM
    CARBONATE and a few others is another mater.

    BTW, I've noticed no odor with weak
    solutions of sodium sulfide. Dan