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  1. #1

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    The impossible project: latex timing layer?

    The website for the Impossible Project, attempting to re-formulate and re-start production of Polaroid 600 integral film, has been updated. The most interesting update is a request for help sourcing a particular type of latex to use as a timing layer. There's a diagram on the website of the film layers, as well as a cryptic (to me) discussion of the chemistry.

    I'm be interested in the comments of photo chemistry experts here as to what they can glean from the I.P.'s request.
    Vince Donovan

  2. #2
    AgX
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    Between the image receiving layer and the clear cover sheet is situated an alkali-sink. Being acid itself it neutralizes the alkali of the developer. And thus stops the development, a bit like the stop bath in classic development.

    The time it takes the alkali to reach this sink is controlled by a timing layer. One can either use a layer with constant permeability or a layer which is corroded in a way by the alkali and will `break´ after some time. The latter resembles more the classic processing where solutions are exhanged in short time.

    To my understanding of the request they intend to use a double layer, as the latex (intented as barrier) is to be coated on gelatin and not directly on the polymeric acid layer.

    The difficulties the manufacture of this part of the layer-assembly would form has been hinted at by PE at the initial discussion of the Impossible Project.

  3. #3
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    If you could give a URL that would help me study their particular situation.

    Basically, AgX has it right. I used to work on timing layers and shutdown layers at EK on some special projects and I know how very hard it is to get this right. Basically, the latext is coated over a polyacrylic acid copolymer. The latex coating must be penetrated before reaching the acid which stops development. This timing layer is critical to getting good pictures and must respond properly over a wide range of temperatures or the pictures will not come out right. Polaroid had a lot of problems with color shifts for this reason.

    But, the bottom line is this. Too many of the original materials needed to make Instant products were made just for those markets and have now vanished. This will make recreation a hurculean task. I wish them well.

    PE

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    AgX
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    Thanks.

    You will note that the image is on top of the timing layer. Kodak's system was not. Therefore, in this case, the entire imaging layer must remain intact and hard. This is the critical issue I think. The latex must be hardenable as well as the acid layer and the recieving (mordant?) layer. The gelatin is rendered very soft by the base and so the hardening must be effective.

    Kodak made their own latexes. Maybe a search of the patents might help. There are several latexes or near latexes that might help, but they are all custom made items. Therefore, they would probably be expensive. I know that one of the Kodak ingredients was found to be a carcinogen and had to be eliminated from the project, so that is another consideration.

    I found another route to the solution, but that is not applicable here as they need timing as well and hardening.

    They have a lot of work ahead of them.

    PE

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    PE, perhaps they could pay you to do some consulting for them?

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    I have not done any of that sort of work since the 80s. I've forgotten most of the details of the timing and acidification layers, but do remember some of the test procedures. I'm afraid that I would be of limited value to them. They have all of the retired or laid off Polaroid people to draw on besides.

    Besides, I'm not really interested. I have too many other things to accomplish that I can do with better impact on the future of analog. I think that you can see the importance of that single point.

    PE

  8. #8

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    Thanks PE and AGX. This is just the discussion I was hoping would break out. I always learn something new on APUG!
    Vince Donovan

  9. #9
    AgX
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    Impossible states that they

    "...could produce the very first complete and stable instant picture a few weeks ago".

  10. #10
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    If there is such a demand for it, why didn't they? After all, they could have sold it!

    PE

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