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  1. #21
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    I understand. I was not criticizing, just trying to prevent an error from creeping in.

    PE

  2. #22
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    AgX, that post is very informative. Good job researching!

  3. #23
    AgX
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    Obviously I need a correcting editor…
    Only after third reading I realized; that not only a prefix got lost but a part of the sentence. Here is the corrected paragraph:

    …A developing agent fixed to the very layer is employed, with a dye coupled to it. Being of a colour complementary to the colour the adjacent halide layer is sensitive to. This agent being oxidised, after reducing the exposed halide, has become insoluble, whereas the developing agent in the non-exposed areas becomes mobile and migrates with its attached dye into the receptive layer, where they are fixed to form an image in the kind of the imbibition technique...

  4. #24
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    AgX , Thank you very much for the text. I will read the patents than ask the questions. I am happy for polaroid and kodachrome legends analysed.

  5. #25
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    One of the patents referenced in one of the patents that AgX listed is very interesting. (Patent # 2352014) It outlines multiple examples of the process, and the majority of them require few, if any chemicals that a photographic chemistry and emulsion experimenter wouldn't have.

    Some of this stuff may be worth a try

  6. #26
    AgX
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    As a clarification:

    That patent 2,352,014 is an US patent of André Rott. I gave his British patent 614,155. However this seems not to be accessible on the net.

  7. #27
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    I've been reading this over and find that one thing is missing......

    SHUTDOWN!

    You see, without shutdown, all processes keep going on and on and on. This is a crucial part of all instant imaging. No one has mentioned it at all.

    If it does not take place, the final image is BLACK.

    PE

  8. #28
    AgX
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    Dear PE

    This is one the very few times that I do not share your view.
    I gave some hints that the development of the negative has to be stopped:

    "The idea behind it is to produce a negative, dissolve the remaining halide…

    The Polaroid technique added to this all the feature of instant development
    (fast, chemicals in pods etc., later even self-controlled with SX-70).

    After processing and forming of a positive image behind the screen by those migrated and developed halides, the second film is torn off.

    As there is no parting of the layers it must be self-controlled."

    Further more this thread is clearly directed at people who have some practical understanding of the common instant processes.


    However the aspect how to save the positive image from being harmed by the remaining halide solvent, developing agent and alkali is even merely paid attention to in the literature I used. With positive exception of the Neblette.
    The only advise feasible for home projects I could give besides washing, is to use resin coated paper for the receptive layer and think of an acid water based lacquer similar to the one used in some Polaroid processes.

  9. #29
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    Well, the overcoating brush used in Polaroid prints is a form of shutdown, but beyond that there can be a polymeric acid layer protected by a water repellanat layer. The base in the pod breaks down the repellant layer and is then further neutralized to the proper pH by the acid layer.

    This is necessary in integral materials and sometimes optional in non-integral materials.

    If you have a peel-apart material, the individual customer can be burned or harmed by the alkali or the other chemistry.

    Without proper pH and removal of harmful chemicals, the image may 'tone' and turn brown or otherwise change in density.

    This is why I bring it up.

    PE

  10. #30
    AgX
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    So again there was a misunderstanding...

    I really thought you had i about the right timing between gaining the right negative density versus the right positive density.

    Yes, the stability of the positive image should be an issue. Strange enough, in the most texts I've read this isn't an issue.
    In one textbook, one that even gave a quite precise description of the process naming those metallic-nulei, stated that no further preservation would be necessary, but a lacquer coating to keep “ the silver image from mechanical damage”…

    As even in the Neblette no principle compilation of the dangers to the image is given, could you give a basic explanation for the most simple case of substances remaining after instant halide diffusion process:

    Silver grain (physically developed as that seems to influence its structure, grown on nucleus)
    Nuclei (noble metal?, sulphide of heavy metal?)
    Developing agent (Chinolate + benzochine)
    Silver solvent (let’s say Na2S2O3)
    Alkali
    Recepting base (let’s say custom gelatinized on outfixed RC-paper)

    This is different from a photo paper that has gone through a normal process but is not washed at all.

    What kind of reactions would/could take place with the surrounding environment and between them?

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