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  1. #31

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    Just for the records; the "overhardening" which I refer to is the phenomenon Colin thinks he is stricken by. (Where presumably more hardener than the ideal will make the sizing soften and cause more swelling...)

    OTOH, it's interesting that glyoxal is able to harden gum but formalin isn't. I seems like formalin works with proteins only whereas glyoxal works both with proteins and polysaccharides!??? Anyway...


    Quote Originally Posted by Katharine Thayer View Post
    ...
    I have seen overhardening of a colloid with a hardener, once, but that was when I was experimenting with using glyoxal to harden gum for a painting application, and tried several different strengths. The gum with too much glyoxal became very hard and crystalline on the surface when it dried, almost in texture as if it were coated with sugar or something. Again, not sure how relevant that is to the question here, just an observation...

  2. #32

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    Well, I just can't make this work at any dilution. Dry, the surface seems very rough compared to glyoxal and when the size does manage to survive development the highlights are very badly stained. Once wet, the sizing always swells and gets very slimy. I've asked Photo Formulary for suggestions, I'll keep using glyoxal until I sort it out. Was having relatively excellent results with it, but the worry of yellow stains showing up is always there.

    But I gotta ask: you are supposed to dilute the glut concentrate with distilled water, correct? I diluted the 24% 1:10 to make 2.4% so maybe I goofed there..Although I did take a cautious sniff of the 'pure' 24% concentrate, and that's completely odorless, which surprised me after the warnings about the stuff.
    Last edited by Colin Graham; 10-10-2009 at 01:03 PM. Click to view previous post history.

  3. #33
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    Fisheyes, as you call them, and craters as others call them, are repellancy spots generated by incompatible materials being coated one on top of the other. They can be best eliminated by adjusting the surfactant in the coated materials. If you have no surfactant, add one. If you have one, change the level or the type.

    Try negatively charged surfactants such as Triton X 200, or neutral ones such as Photo Flo 200. Use very little as the surfactant response is such that it gets you out of trouble at the right level but causes woes when absent or when present at too high a level.

    PE

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