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Thread: A real formula

  1. #101

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    Hello, PE
    I've been reading yours and others emulsion formulas in this forum, and I'm very interested in making my own emulsion, for papers. I really want to find a simple recipe of enlarging paper emulsion which doesn't need washing and that I could coat on artists canvas, too. In a brazilian book (Formulário fotográfico, by Reinhard Viebig), I found this one, and I wonder if you could give me tips or see if it will do the job. I'll translate the recipe:

    Emulsion for Papers:

    To emulsify any paper, you should first coat a layer on the support to be emulsified, with a fine brush or sponge. This layer consists of the following formula:
    Potassium Iodide - 13,0 g
    Potassium Bromide - 75,0 g
    Starch - 17,0 g
    Water to make - 1,0 liter

    The emulsified paper, when dried, must be sensitized in the following solution:
    Silver Nitrate - 50,0 g
    Distilled Water - 1,0 liter

    Let the paper float on this liquid and put it to dry in a dark place. Exposure, developing and fixing follow the normal processes used for ordinary bromide paper.

    I found it interesting because it doesn't need washing as (I think so) the precipitate will fall on the Silver Nitrate solution container. It is not said, but I suppose that a starch glue should be made from the starch, and that will adhere the KBr and KI to the paper.
    Do you think if I add some Thymol to the emulsion, its shelf life will be greater? Also, do you think it's a good idea to add the Silver Nitrate solution to the emulsion solution with more starch glue, and then coat it on paper/canvas, without washing?
    Here in Brazil, it is impossible to find photograde gelatins, so this emulsion is very convenient, since it's easy to find cassava starch in the market.
    I hope you can help me.
    Thank you!

  2. #102
    Photo Engineer's Avatar
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    Well, to start with, this is not a typical silver halide emulsion. There is no gelatin involved. This is another type completely. It is outside the scope of my work.

    I might add that many paper emulsions were unwashed, even with gelatin.

    PE

  3. #103

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    Quote Originally Posted by Photo Engineer View Post
    Well, to start with, this is not a typical silver halide emulsion. There is no gelatin involved. This is another type completely. It is outside the scope of my work.

    I might add that many paper emulsions were unwashed, even with gelatin.

    PE
    Ok, thank you!
    It's good to know that I can make silver gelatin emulsions without washing. I'll try to buy gelatin on ebay and give it a try. I don't like the sensitization mode of this recipe I posted... it may waste too much silver which is not cheap at all.
    Can I use the emulsion formula you posted in this thread for enlarging paper coating?

  4. #104
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    The formula here, using ammonia, is not an enlarging speed emulsion. The enlarging emulsion uses no ammonia.

    PE

  5. #105

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    Quote Originally Posted by Photo Engineer View Post
    The formula here, using ammonia, is not an enlarging speed emulsion. The enlarging emulsion uses no ammonia.

    PE
    I found a very simple recipe in this forum that was tested, and you mean there that if I want a enlarging-speed emulsion, I should make a sulfur finish in the emulsion.
    The link for the thread is the following: http://www.apug.org/forums/forum205/...mulsion-2.html
    Could you explain to me what sulfur finish would be? If I don't do this sulfur finish in the emulsion, will it be really impossible to use it for enlarging?
    Sorry for taking your time...

  6. #106
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    Sulfur finish increases speed and contrast of an emulsion. In an enlarging speed emulsion, it is usually added at 100 mg of Hypo (pentahydrate) per mole of silver. This is based on grain size, and so a finer grained slower emulsion would need more and a coarse grained emulsion would need less.

    You bring the emulsion to 60 deg C, add the hypo solution while stirring, and heat for 1 hour. You then cool. This is a normal operation, but temperatures may vary as well as hold times.

    PE

  7. #107

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    Thank you very much, PE! You helped me a lot.
    Also, I think it's a good idea to add some Potassium Iodide to this formula, as it will increase contrast and speed too... am I right, or this is not a good idea in a unwashed emulsion?

  8. #108
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    You can use Iodide for this purpose but you must be careful or you will fog the emulsion. The question of how much and when to add it is critical and varies with each emulsion.

    PE

  9. #109
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    Looking for dyes, additives or a formula to sensitize collodion to >800nm (infrared)

    After reading your giant thread, I'm a little confused. But I am convinced, that you, PE, are the 'right man'.
    There are lots of hints and advices for dyes to create an emulsion with super-panchromatic or, at least, expanded red or infrared sensivity. But these formulas are all just for dry plates.

    My collodion plates are just sensitive to blue light.
    After production of Kodak HIE was stopped and there was no other real infrared film material on the market anymore (forget Rollei and SPX, just 700nm / EFKE and Konica stopped production) there is no chance to continue real infrared photography.
    So I just wanted to try some dyes to expand/shift sensitivity up to 800 or more nm with collodion wet plates.

    The wet collodion process is devided in two parts.
    1. The collodion
    2. Sensibilization in silver nitrate sol.

    Where, when, how and how much do I have to add the Neocyanine or the 3,3'-Diethyloxatricarbocyanine iodide.
    Do I have to change the developer (iron(II) sulfate), then?
    How about fixing, then? Any experience?
    If it doesn't work with collodion, what is the exact procedure for IR-sensitive dry plates (up to 800-820nm or more)?

    Sorry for creating another thread already in APUG. I'm a newbie here and I'm not used in the system, yet.

    ...and sorry about my horrible English!
    Thanks

    Frank

  10. #110
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    AFAIK, wet plate collodion has never been sensitized to anything other than blue. It is pretty much impossible to do with the technology invented for silver gelatin.

    However, you might find a way if you are willing to experiment.

    The method is very simple. You add the dye just before coating the silver halide on a plate or film. Usually, you hold the warm emulsion for 15 minutes. Then you ad any finals. Then you coat.

    The amount of dye is based on grain size and can vary from 10 - 100 mg for every mole of Silver ion present. That must be determined by trial and error. Once set, it is firm at that level.

    PE

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