On Thu, 18 Mar 2004, Ryuji Suzuki wrote:
> ... frankly I was a bit surprised that you said glyoxal
> worked for gum. Maybe there are other positively charged groups that
> can strongly bind with aldehyde.
I don't recall ANYONE saying "glyoxal worked for gum." As far as I know,
gum printers use glyoxal only to harden the GELATIN size on the paper on
which they will use some other colloid, said colloid being hardened by the
action of dichromate.
I think Katharine was speculating about a hardener for gum arabic for some
other purpose -- nothing to do with this discussion about how best to
harden gelatin as paper size. (And I note that some printers don't
harden their gelatin size at all, relying on the tanning action of the
dichromate for that.)
Again, having read a whole bunch of "authorities" on this & that, I reveal
-- stop the press !!-- that their "knowledge" is terminally theoretical
(and ever subject to revision) & not to be extrapolated across the board
without physical verification. I'd be dubious whether it could even be
applied across the board to all "gelatin." There are so many... If they
were all the same, why would G. Eastman & co spend millions to make their
own? A 300 bloom "porcine product" works the same as 150 bloom cow feet?
I doubt it...
Judy
Received on Thu Mar 18 18:23:52 2004
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