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  1. #11
    neelin's Avatar
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    from: Photographic Facts and Formulas, E.J. Wall & Franklin I. Jordan (orig. 1924) revised & rewritten by John S. Carroll 1976. ISBN:0-8174-0580-1 (Amphoto) p141

    "Another approach to desensitization is to convert the silver bromides in the emulsion to iodide, which is much less sensitive to light, and allows developement of the image in bright light. This was first noted by R. Freund in 1908, and followed by extensive investigation by F.F. Renwick in 1920. If an exposed emulsion is bathed for several minutes in the following bath

    Potassium Iodide 10.0g
    Sodium Sulphite (dessicated) 10.0g
    Potassium thiocyanate 30.0g
    water to make 1.0l

    it could be developed even in full sunlight, using amidol (diaminophenol) developer freshly commpounded with sodium carbonate. There is some question if this will work with modern, high speed, dye-sensitized emulsions"


    I wonder if the last sentence was written by Carroll in 1976 or Wall-Jordan in 1924

    robert
    Last edited by neelin; 06-26-2009 at 11:16 AM. Click to view previous post history.

  2. #12
    Ian Grant's Avatar
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    Frank Renwick was of course a Research Chemist at Ilford, in Essex, at that time, which is prior to his stint at Dupont in the US, he later returned to Ilford as Head of Research. The comments will be John Carroll's.

    Ian

  3. #13

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    Thanks to everyone who is commenting. I went to M and P site....one of the options is to use IR devices which evidently make the entire process of DBI very easy. I also found a copy of Steve Anchell's great reference book, the Darkroom Cookbook. He mentions one desensitizer that is still available, i.e., De-tec made by Antec ( www.kyantec.com )....and yes, the product is still available. Mr. Anchell points out that pyro developers will desensitize the film, but one has to judge the highlight densities differently. I'm not sure that I will attempt DBI...sounds a bit intimidating. However, I can see where being able to be a bit "liberated" from time and temperature would be interesting.

  4. #14
    Ian Grant's Avatar
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    Interesting comments about D-Tec working less well with D76, D23 etc presumably Xtol too, and potentially causing fogging with Pyro developers.

    Since M.A.S. wrote that article the cost of IR devices has dropped significantly, and they are a lot much more readily available,

    Ian

  5. #15
    Jim Noel's Avatar
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    I regularly develop by inspection. At this moment I have ten students developing lith film to long scale under s red safelight. The next step is to teach them to develop FP4+ utilizing a green safelight for a few seconds at a time after the film is 65-75% developed according to time/tempeerature charts. The secret is knowing what the film should look like for a particular DR. This takes practice.
    [FONT=Comic Sans MS]Films NOT Dead - Just getting fixed![/FONT]

  6. #16

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    How interesting Jim! Where are you teaching such skills, and why did you decide to teach DBI? Other than M and P, I wasn't aware of anyone who is actually teaching DBI.

    Ed

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