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  1. #21
    donbga's Avatar
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    Quote Originally Posted by Colin Graham View Post
    I standardized on 20% AD, but count drops like any other process. I also started pre-making dispersions of watercolor pigment and gum in known and repeatable concentrations. While that's hard to measure by dropper because of the viscosity, it does measure accurately in one of those graduated cough syrup spoons and gives much more consistent results than weighing- unless you have a very sensitive scale.
    Well FWIW, as mentioned before I use AD in a 'saturated' state. I meter the volume with a medical syringe which seems to be very accurate. I then add an equal volume of distilled water (BTW, I always use distilled water for AD solutions) so in the end I'm using about a 15% solution. I've heard several gum printers remark that much less dichromate can be used than many people typically use including myself.

    One very well known and experienced gum printer has told me about his method and he seems to use very small amounts of dichromate by comparison. But as in all things gum everyone uses what works for them.
    Don Bryant

  2. #22

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    That's Sam I presume. (See: http://unblinkingeye.com/Articles/3CG/3cg.html) He is using an effective solution strength of 6% - I mean in terms of 1:1 gum/pigment+dichromate... I've started with 20% AD and reduced it to 5%, until I was getting good results with my procedures. Not a coincidence then...

    Regards,
    Loris.

  3. #23

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    I do the same thing Don does. When mixing my final solutions, I measure out the same amount of water as the Am Dichromate, thus diluting it. Sometimes I substitute more gum arabic for the water as well. So the final solution of Am Dichromate is not saturated. The jar of saturated solution, used as a stock, is just for convenience.
    Steve
    www.scdowellphoto.com

  4. #24

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    Many thanks for sharing your approaches, very informative. Good to know there is latitude in the process. I sometimes am too rigid to change things or explore more options once I get a little success with a certain approach.

  5. #25
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    Quote Originally Posted by donbga View Post
    Well FWIW, as mentioned before I use AD in a 'saturated' state. I meter the volume with a medical syringe which seems to be very accurate. I then add an equal volume of distilled water (BTW, I always use distilled water for AD solutions) so in the end I'm using about a 15% solution. I've heard several gum printers remark that much less dichromate can be used than many people typically use including myself.

    One very well known and experienced gum printer has told me about his method and he seems to use very small amounts of dichromate by comparison. But as in all things gum everyone uses what works for them.
    In case anyone is wondering for carbon printing - exact dilutions need to be used.
    Don Bryant

  6. #26

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    Where do you guys get bottles for storing stock solution? I've been trying to track down a 100ml brown bottle but no luck, other than a plastic cough syrup bottle the guy at the drugstore gave me. If only I still worked in a university lab...
    The universe is a haunted house. -Coil
    .

  7. #27

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    Or would a plastic (brown) bottle work? I'm not sure if the dichromate is reactive against plastics.
    The universe is a haunted house. -Coil
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  8. #28

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    Walter,

    Have you tried other drugstores? Maybe they can lead you to a retailer or sell some bottles from their stock? I buy mines from the chemisty store, usually in numbers of 10. (Since they're so cheap.)

    http://www.57aromas.com/category/Amber
    http://www.aquariusaroma-soap.com/in..._58_197_250_62
    Last edited by Loris Medici; 03-02-2010 at 03:11 PM. Click to view previous post history.

  9. #29

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    Ebay, B&S, Photo Formulary all sell them in many sizes but sometimes you have to ask if it's not in the online catalog.

  10. #30
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    I've heard of situations like this with UV cured printing processes. The curing process apparently changes the adhesion properties of the ink surface causing the next layer to not adhere to the first ink layer. In this case I wonder if there is some way to create more tooth on the surface of the first cured pigment layer so the next will be able to bond properly to it.
    Gary Beasley

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