On Sun, 15 Feb 2004, Christina Z. Anderson wrote:
> However, one observation I'll have to corroborate the next time I size: the
> glyoxal gelatin solution seemed yellower today than last night. Whether
> this leads to any explanation of the yellowing controversy we have discussed
> here, who knows. It was kept at 140-120 degrees for 15 hrs and is yellower.
> Any suggestions, chemists and gum printers? When brushed on the paper, the
> yellowing in a thin coat of size is not apparent so no biggie. Plus I'll be
> using it right away so it won't sit in a drawer to get yellower...
Of course I repeat myself, but my suggestion is to apply the hardener as
a separate coat -- you save all kinds of variables that occur when it's in
the gelatin, including the aging and hardening of the combo... (Of course
on the other hand, who knows what interesting creatures you could grow in
a gelatin culture kept at 120 degrees for a day or two...)
I also suspect that you'd use less glyoxal, which is a lot more expensive
than gelatin... That is, unless you're brush coating the gelatin too...?
For a separate hardening bath, I use 15 ml glyoxal per litre of water (the
same amount I used for formaldehyde)... the sheets can be hardened a few
at a time so a shallow tray full is OK... I rinse the paper after
hardening -- and do not see any yellowing.
J.
Received on Mon Feb 16 00:59:43 2004
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