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  1. #11

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    Personaly, between chrome alum , Glyoxal and Formalin, I have never observed an advantage in chrome alum over the other two hardeners. Glass plates are the only kinde of emulsions I make. Glass cleaning is vastly more important than glass adhesion promoters. While it is true that my emulsions contain silane, If I don't clean my glass to the standard of a "standing sheet" of water, I WILL see frilling and cratering. Please see my glass cleaning proceedure on www.thelightfarm.com and www. alternativephotography.com. Also, one must be very careful of the type and amount of surfactant one uses when the substrate is glass. The wrong kind, or too much surfactant can realy destroy adhesion to glass. I like Triton X200, in tiny amounts.
    Bill

  2. #12
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    Use chrome alum in emulsions for glass coatings. For film coatings use an aldehyde hardener or use chrome alum but with a longer drying time before use. Chrome alum is slower to harden. The old writers note that emulsions can be stored in the cold with chrome alum for quite some time.

    Use of Chrome Alum or Glyoxal are best done at the same quantity per unit of gelatin and so I use 10% Chrome alum or I dilute commercial 40% Glyoxal to 4% (I call it 10% Glyoxal) and use either at the rate of 5 ml / 120 grams of 10% gelatin. The Glyoxal will harden in 4 - 8 hours, but the Chrome Alum requires about 24 - 36 hours.

    PE

  3. #13

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    PE, is there a significant difference between glyoxal and glyoxal trimer dihydrate (CAS 4405-13-4) that makes the latter unfit for adding to emulsion? The acrylic-primed canvas has been prepared with the mixture of gelatin and isopropyl alcohol.

  4. #14
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    Glyoxal trimer is probably similar to the Formaldehyde trimer that forms from Formaldehyde. I have never worked with the trimer, but I can tell you that it must be hydrolyzed to the monomer before it can work properly. The Formaldehyde trimer works but much more slowly than Formaldehyde itself.

    That is about all I can tell you, never having worked with it before.

    PE

  5. #15
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    Regarding the trimer of Glyoxal:

    The trimer when dissolved to produce a weak solution will revert to the monomer within 24 hours (in darkness).. so claims a paper on the fixation of tissue samples. Unfortunately, it doesn't supply quantities, but does reference a another paper - Earl B. Whipple, "The Structure of Glyoxal in Water". So far I haven't been able to find a free copy of Whipple's paper - JACS wants $$ to read
    - Ian

  6. #16
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    Then I would use the trimer mole for mole re glyoxal and wait 24 hours before using it.

    PE

  7. #17

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    Hexavalent and PE, thank you for the info. I will then try dissolving the glyoxal trimer in water. Should I use distilled water? What might be the trimer : water ratio?

  8. #18

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    Trimer = polymer consisting of 3 identical subunits/precursors.

    So the ratio would be 3 water to 1 trimer. But I suspect you want to use a bit more water than that...
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  9. #19
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    To allow this to form Glyoxal, I would use 40 grams of trimer and 60 grams of DW to make a standard 40% wt/wt solution. Then I would let that stand for about 2 days and then I would dilute it to working strength by taking 10 g of the Glyoxal and adding 90 grams of water to make a (10%) 4% wt/wt working solution. I would refrigerate everything after this and only take the working solution out as needed.

    PE

  10. #20

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    Hi there,
    I mixed the silver bromide emulsion in 125 ml. Can someone tell me how many grams of chrome alum I should add in?

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