Liam Lawless' Enlarged Negatives by Reversal Processing?

Discussion in 'Enlarging' started by John W, Apr 10, 2009.

  1. John W

    John W Member

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    Does anyone know of a current way to get Liam Lawless' article Enlarged Negatives by Reversal Processing? The original version of the article was in The World Journal of Post-Factory Photography #2, but the email address for Judy Seigel to obtain back issues no longer exists (domain is gone). The updated version from http://rmp.opusis.com/documents/reversal4.pdf is gone as well, nor is it available via archive.org.

    Liam appears to have had a website at http://www.silver-print.com/ at one time, but that's gone as well.
     
  2. payral

    payral Member

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  3. Lukas Werth

    Lukas Werth Member

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    I think I do have a downloaded pdf still somewhere on my hard-disk at home. Give me some time, I will attach it.

    However, I am using this process regularly, and I would recommend quite some alterations of Liam's original instructions. I think I have made notes about this somewhere on Apug not too long ago.
     
  4. dancqu

    dancqu Member

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    Check at www.unblinkingeye.com . Just checked.
    I was sure the article WAS there. I've read the article at
    that site. Odd it's gone. Liam has a few other articles
    there. I'll miss it. Dan
     
  5. BobNewYork

    BobNewYork Member

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  6. Jon King

    Jon King Member

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    There were updates, mainly simplifications to his process in The World Journal of Post-Factory Photography #3 and #4. Judy Seigel is active on the alt-process-photo list.
     
  7. John W

    John W Member

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    Yep, that was one of the first things I tried as I mentioned in my original post. Thanks for the thought, tho!
     
  8. John W

    John W Member

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    Thanks for looking for the article, Lukas. I'll search APUG for your process notes.
     
  9. dancqu

    dancqu Member

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  10. yellowcat

    yellowcat Member

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    A few years ago I made a number of enlarged negatives for a client who wished to use them for making cyanotype prints.
    I printed the negatives onto Ilfochrome ohp film and with a little experimenting was able to get good results. My client was very happy with the enlarged negatives.
     
  11. payral

    payral Member

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    I checked my hardrive and found the Liam's file.
    So here it is attached. I hope it will help
     

    Attached Files:

  12. dancqu

    dancqu Member

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    Is there some reason potassium ferricyanide would
    not work? Also, would not sodium bisulfate work? It
    is a suggested substitute for sulfuric acid. Dan
     
  13. John W

    John W Member

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    Dan, there are several classes of silver photographic bleaches, with different actions on the silver in the film. (**) For a reversal process, a bleach is needed that converts the exposed silver to a form that is soluble in the bleach. For potassium dichromate + sulfuric acid, the silver is oxidized to silver sulfate.

    So in the reversal processing sequence, we have:
    1) Unexposed film, no image -- unexposed silver halogen salts.
    2) Exposed film, latent image -- exposed and unexposed silver salts.
    3) Developed film, silver positive image -- metallic silver and unexposed silver salts.

    In normal processing, we'd fix now, removing the unexposed silver salts, leaving behind only a metallic silver image. Reversal, however, continues on like so:

    4) Bleached film, metallic silver removed -- unexposed silver salts.
    5) Washing and clearing
    6) Reexposure, latent image -- exposed silver salts.
    7) Redevelopment, silver negative image -- metallic silver.
    8) Washing
    9) (optional) Hardening

    Potassium ferricyanide is used as a re-halogenating bleach, where the silver is converted back to a halogen form (e.g. with bromide to achieve Ag -> AgBr), which must then be removed by fixing. This creates a problem during steps 6 and 7 above, since the silver salts from the bleaching would result in nasty image fog.

    (**) I'm going from memory on the bleach info, hopefully someone will correct if I've misstated anything. Mean library :smile:D) took back Mason's Photographic Processing Chemistry, and my copy of Haist's Modern Photographic Processing hasn't arrived yet.
     
  14. dancqu

    dancqu Member

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    I mentioned only potassium ferricyanide. No mention of
    re-halogenation was made. Likely ferricyanide is not used
    because silver ferrocyanide is highly insoluble while silver
    sulfate is very slightly soluble.

    After posing the question I pondered some. So the
    reversal process produces silver sulfate. Dan
     
  15. John W

    John W Member

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    Right; I'm rather new to photographic chemistry, so I kind of ran off with the common use of potassium ferricyanide as in the formulation for sepia toner... blasting right past using it alone as a bleach. I note that this article on blue toning by Liam Lawless confirms that the silver ferrocyanide can be removed by fixing, something I'd only just assumed earlier.
     
  16. ghost

    ghost Member

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    pot ferri IS a re-halogenating bleach- a completely different type of chemical action than what is needed for this process- that's what he was trying to explain to you my man-
     
  17. dancqu

    dancqu Member

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    You've made clear the two bleach methods. Bleaching for removal
    of the silver image does call for the silver's conversion to a soluble
    form. Checking for solubilities I find the permanganate to be
    9 grams per liter and the sulfate 8.3 grams.

    A post fix image bleaching with potassium ferricyanide ALONE
    leaves an image of silver ferrocyanide. Following toner or
    redevelopment results will likely differ from those of a
    halogenated image. I'm going to check on that. Dan