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  1. #11
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    Quote Originally Posted by sanking View Post
    I have no idea if it will serve your purpose but one could buy a 300 Bloom gelatin from the United States Biochemical Corporation.

    http://www.usbweb.com/category.asp?cat=118&id=16047

    Unfortunately you might have to have someone in a lab or at a university buy this for you as last time I checked they did not sell directly to individuals.

    Sandy King
    Sandy;

    This is pig gelatin which has a vastly different isoelectric point. IDK of ever hearing of it being made into a PA gelatin.

    Hans;

    From what I know, your results or lack thereof is not unusual in making PA gelatin.

    PE

  2. #12

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    Could you please explain how to de-salt gelatin? What impact does this have on the results?

    Thanks from,
    Emulsion.

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    Could you please explain how to de-salt gelatin? What impact does this have on the results?
    An easy way to de-salt gelatin is to cut a gelled gelatin into small cubes or shred it to noodles. Then wash those gelatin bits in several baths of de-ionized water. This procedure removes most of the salts that have remained in the gelatin during it's manufacture. If those salts are not washed out before precipitation of the AgBr grains upredictable or unwanted results can occur. For example: If a lot of chloride ions are present in an unwashed gelatin, this can cause unwanted grain growth during the precipitation stage.

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    Ok, my last test worked. This time I introduced the phthalic anhydride below the surface of the gelatin instead of dropping it in.
    Also, I made a fresh solution of the anhydride in Acetone (I don't know if that solution spoils, but I did not want to take any chances).
    And, I did the reaction at a slightly higher PH of 10.5.

    This time the gelatin precipitated as very fine particles when I lowered the PH to below 4. I think that for washing the gelatin the procedure might not be very suitable. At least not with ultra-fine grains because it takes quite a while for this precipitate to settle to the bottom of the glass jar. All this time the emulsion needs to be warmer than 32C and this increases the grain size. But then, I did not really do the experiment for washing the gelatin, but rather to see if I get a better emulsion with the phthalated gelatin.

  5. #15
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    Remember that the gelatin will coagulate faster in the presence of silver halide. In fact, if you use all phthalated gelatin at the start of the precipitation, you will get a putty like coagulum. It will also generally give you finer grains. This might be of some benefit. I have posted a picture of this here on APUG.

    You may want to consider UF wash though.

    PE

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