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  1. #51
    Photo Engineer's Avatar
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    Basically, film support and resin support used in RC papers repel water and therefore they repel gelatin in water. A special material that adheres to film support or the resin and is porous enough to allow gelatin to adhere to it is ideal as a subbing.

    If a plain polymer is used, it might work, but then as soon as you dipped the film into water for processing, the polymer would dissolve and allow your emulsion layer to float off in a thin sheet. Therefore, not any polymer will do. It must be hardenable or must somehow set up permanently while still allowing the emulsion layer to adhere.

    At the same time, it cannot be too acidic or basic or oxidative or reductive, otherwise you mess with the emulsion.

    See how easy it is?

    PE

  2. #52
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    Can someone give me more information on Baryta support from Bergger? A contact or something? Someone who has actually purchased some?

    Thanks.

    PE

  3. #53
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    I found an interesting item in an Ebay ad, Kodak roller transport cleanup film 4955. It's basically film base with a layer of gelatin coated on both sides. Someone needs to try this with Liquid emulsion and see what happens. It would make it possible to shoot hand coated film in standard film holders.
    Gary Beasley

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    Quote Originally Posted by glbeas
    I found an interesting item in an Ebay ad, Kodak roller transport cleanup film 4955. It's basically film base with a layer of gelatin coated on both sides. Someone needs to try this with Liquid emulsion and see what happens. It would make it possible to shoot hand coated film in standard film holders.
    I think this would make a great support for Carbon tissue....where is the auction?

  5. #55
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    Heres the link :

    http://cgi.ebay.com/ws/eBayISAPI.dll...ADME:B:WN:US:1

    I think Kodak still supplies it. You might contact the buyer, I'll bet they were after the Tmax and care nothing about the transport cleaner and may sell it to you.
    Gary Beasley

  6. #56

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    Quote Originally Posted by glbeas
    Heres the link :

    http://cgi.ebay.com/ws/eBayISAPI.dll...ADME:B:WN:US:1

    I think Kodak still supplies it. You might contact the buyer, I'll bet they were after the Tmax and care nothing about the transport cleaner and may sell it to you.
    Thanks Gary, I might just do that..

  7. #57

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    The manufacturers usually apply corona discharge treatment to the surface of polyester film and sub the surface with styrene butadiene latex copolymer or something similar. But they probably have more efficient methods by now. (Years ago they used one or more extra steps of subbing before gelatin layer) Once the polyester is thus subbed, the surface is ready to accept aqueous gelatin coating. Cellulose triacetate film is a lot easier in this regard. (That's why a lot of films made by low-tech manufacturers use triacetate base.)

    In terms of the polymer technology that went into the film base, APS films are the top. They specifically designed a kind of polyester (annealed poly(ethylene naphthalate)) which is just as durable as PET but doesn't curl. I think only APS-participating manufacturers have this technology. (The process to make this type of film base is a lot more involved than plain PET film base.)


    Quote Originally Posted by Photo Engineer
    Basically, film support and resin support used in RC papers repel water and therefore they repel gelatin in water. A special material that adheres to film support or the resin and is porous enough to allow gelatin to adhere to it is ideal as a subbing.

    If a plain polymer is used, it might work, but then as soon as you dipped the film into water for processing, the polymer would dissolve and allow your emulsion layer to float off in a thin sheet. Therefore, not any polymer will do. It must be hardenable or must somehow set up permanently while still allowing the emulsion layer to adhere.

    At the same time, it cannot be too acidic or basic or oxidative or reductive, otherwise you mess with the emulsion.

    See how easy it is?

    PE

  8. #58

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    I have Tani's book, from which I learned A LOT, but I have to warn you. Tani's main interest is the mechanism by which light exposure is registered in silver halide crystals. His book gives a very concise general account of how emulsion is made, but the setup is very schematized and the book isn't aimed to describe how to make emulsions. This is a very scientific book. If you are an emulsion maker with good background in material science an d electrochemistry, you'll learn a lot from this book, but otherwise this is simply a wrong book to consult.



  9. #59

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    The first one is a good dye to use, but unless you use a supersensitizer together, the speed won't be very good.


    Quote Originally Posted by Ian Grant
    If you had to you could try these for starters :-)

    1, 1'-diethylcarbocyanine chloride (was marketed as sensitol red in the 1930's)

    or 2-p-dimethylaminostyryl-pyridine methiodide

    Both found in 1930's publication and with referance to Eastman Kodak Research laboratories.

  10. #60

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    Those old German formulae are obsolete and not useful today, because gelatin they used is very different from gelatin available today. One large factor in high quality emulsions Germans could made in 1930s is because they had a wide range of gelatins available, and they blended depending on the application at hand. Today, quality of gelatin is managed in very different ways. Impurities present in 1930s gelatins are largely removed. It was the impurities that played important role in old emulsion making practice. Today, emulsion chemists introduce those "impurities" deliberately in the reacting vessel instead of relying on empirical gelatin blending.

    I have much of relevant BIOS and FIAT reports but they are only good for historical studies...

    Speaking of historical literature, there are very comprehensive books on industrial chemistry of photography in 1920s, written by a famous AGFA chemist who later came to work for ANSCO. Unfortunately all of his books are written in German language. (I have a copy of the most interesting one.)

    Quote Originally Posted by Ian Grant
    Actually as someone who patented a photographic process / emulsion there is not much you can really do in practice as very small differances would get around it.

    For easons of commercial secrecy companies don't publish their formulae.

    The best (and only) source of good published emulsion formulae was made available after WW11 by the Allies when they translated all the Agfa Gevaert formulae. The books are quite difficult to get hold of, I employed a consultant in the 70's who happened to be related to the Lumiere family, (of Autochrome fame) and had acquired their copies.

    These books went into great detail of all the manufacturing and coating techniques, I copied what I needed at the time.

    Ian

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