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  1. #1

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    Exposing silver halide to light, reversable reaction?

    I am posting this question out of curiosity. I was reading on sepia toning, and use of a ferricyanide bleach to convert silver to silver halide. this as you all know is also done in other processes such as c41, e6 and RA4; (a few atoms of silver form when exposed making the halide crystal developable). Now what if you expose, then decide you want to re-use the film/paper/emulsion without developing it, so you bleach it with ferricyanide or other bleach, (converting the few silver atoms back to silver halide), wash it with distilled water and let it dry (all in the dark or under appropriate safe lighting if the film is ortho)
    If this works how i think it does, then surely you can "re use" any silver halide product if you say shoot it, then find you want to shoot something better.... I would love to try it but lack any bleach (anything other than ferricyanide?) as i dont have my RA-4 chemicals yet and am out of C-41)... would be an intresting thing to try....

  2. #2
    Luseboy's Avatar
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    I'm not so sure that this would work, but i really don't know. I'm interested to hear what you find out. try it!

  3. #3

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    The practical answer to your question is no because various chemicals like sensitizers are removed from the emulsion. What is left is silver halide which is sensitive to light but will not react in the same way as the original film or paper.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  4. #4
    Photo Engineer's Avatar
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    This can be done, but it causes the film to lose all of its original sensitivity due to the destruction or disruption of the grains and the original chemical and spectral sensitization placed on the grains by the manufacturer. The film emulsion reverts to a simple blue sensitive emulsion with low speed, usually in the ISO 3 - 40 range if you are lucky. If it is high enough in iodide, you may actually fog the emulsion totally.

    This subject comes up from time to time. It is a common minconception.

    Also, no rehal bleach should be attempted with a color film or paper bleach. The ammonia content is enough to dissolve a fair portion of the finer grains rendering the film or paper useless. Any rehal process must be conducted in an environment free of any silver halide solvent.

    PE

  5. #5

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    This question reminds me of the magical pill said to have been discovered in the middles ages that would cure any disease. Not only that but the pill could be used over and over. How the pill was to be recovered was sort of glossed over.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  6. #6
    Marco B's Avatar
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    Quote Originally Posted by Gerald C Koch View Post
    This question reminds me of the magical pill said to have been discovered in the middles ages that would cure any disease. Not only that but the pill could be used over and over. How the pill was to be recovered was sort of glossed over.
    The modern equivalent of that tale of course being the nuclear industry promising to cure our climate problems and solve our infinite demand for energy, without ever answering the question what to do with all the waste they generate, nor answering direct safety issues, the likes of which we saw in Russia and Japan...

    And to be honest, in terms of nuclear energy, I am pretty sure human failure (or should I say megalomania?) is probably the worst of the two major causes we can count on to haunt us again in an unavoidable future disaster...
    My website

    "The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true." - William M. Ivins Jr.

    "I don't know, maybe we should disinvent color, and we could just shoot Black & White." - David Burnett in 1978

    "Analog is chemistry + physics, digital is physics + math, which ones did you like most?"

  7. #7
    Marco B's Avatar
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    But to get back on topic, get the nice small book by Rober L. Shanebrook that Photo Engineer was so kind to announce in this thread:

    How does Kodak make film:
    http://www.apug.org/forums/forum205/...make-film.html

    After you've read just the first few pages, or skimmed it's pages, it should be without doubt what high tech product modern film is, and that your question is answered by a resounding no...
    My website

    "The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true." - William M. Ivins Jr.

    "I don't know, maybe we should disinvent color, and we could just shoot Black & White." - David Burnett in 1978

    "Analog is chemistry + physics, digital is physics + math, which ones did you like most?"

  8. #8
    Photo Engineer's Avatar
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    And, the only practical way to save analog is to create a broad base of you people who know how to make their own film and paper in their own darkroom. You APUG members are the only ones Bob and I can rely on that we can teach. But, it seems that very few are willing to learn. So, Marco, what to do about it? I'm stuck.

    PE

  9. #9
    Marco B's Avatar
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    Quote Originally Posted by Photo Engineer View Post
    And, the only practical way to save analog is to create a broad base of you people who know how to make their own film and paper in their own darkroom. You APUG members are the only ones Bob and I can rely on that we can teach. But, it seems that very few are willing to learn. So, Marco, what to do about it? I'm stuck.

    PE
    Maybe its about time we get used to the look of single coated natural non-sensitized blue sensitive emulsions again... and scratches, and dust and all other things that haunted 19th century photographers

    Although Robert's book has fully opened my eyes to what high tech and extremely well thought out productions plants Kodak and other major film manufacturers have put down in the past to overcome all of these problems, and to deliver us the highest quality and most reliable and cosistent films ever in the history of photography, reading the booklet also made me fully aware that such advanced factories will never be cost effective unless a significant bulk demand for film remains.

    The length to which Kodak, and probably other companies like Fuji and Ilford, have gone to create a highly consistent and reliable production process, is astounding as seen from Robert's book...
    My website

    "The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true." - William M. Ivins Jr.

    "I don't know, maybe we should disinvent color, and we could just shoot Black & White." - David Burnett in 1978

    "Analog is chemistry + physics, digital is physics + math, which ones did you like most?"

  10. #10
    michaelbsc's Avatar
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    Quote Originally Posted by Marco B View Post
    Maybe its about time we get used to the look of single coated natural non-sensitized blue sensitive emulsions again... and scratches, and dust and all other things that haunted 19th century photographers
    I don't think we need to accept that. I am trying to make plans to go to PE's next class. And I think others will too.

    Do I think there will be throngs of people making cottage film in 20 years? No. But I think the art will live.

    I think one issue about class attendance is getting the word out. I wonder if the slick magazines like Pop Photo would offer a public service announcement.

    Another issue I perceive is that what Ron and Bob probably should be doing is "Train the Trainer" classes rather than end use classes. Not that I think there's any market for that yet either, but for people to keep it alive in their home darkrooms there probably needs to be at minimum a handful of art schools teaching the techniques.

    I remember years ago my roommate was an art major, and I was surprised at what an excellent metallurgical education he got in the art department. Far better than the Materials Science guys got. When he started grousing around about making sculptures the department head helped him make several bronze castings. I'm here to tell you that a 4 foot high bronze statue might fit in the trunk of your car, but it will overload it for sure.

    That's the kind of programs we need.
    Last edited by michaelbsc; 05-13-2011 at 05:31 PM. Click to view previous post history.
    Michael Batchelor
    Industrial Informatics, Inc.
    www.industrialinformatics.com

    The camera catches light. The photographer catches life.

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