We have established glyoxal as a much improved hardener for gelatin size.
A while ago a chem professor at school mentioned in passing
that the cross-links formaldehyde makes in gelatin (cause of the
hardening) can reverse, or unlink, in water. That, I thought, could be why
size tends to wash off after many, or long, soaks. I asked if
glyoxal-hardened gelatin would act the same way.
Most likely, he says, and quickest in acid. Therefore, advice is to add an
alkali to the hardening agent -- a "buffer." Light bulb! A few
formulas for formaldehyde hardener have added sodium carbonate
(15g/litre as I recall), though nobody ever said why. That could be why.
Chem prof suggests 10g/litre working solution and suggests sodium carbonate
rather than ammonia, which could bring other problems.
Another note on glyoxal: It's so odorless that when a student used it in
class I never noticed until I saw the empty gallon jug, whereupon I chased
her and tray outdoors. But just because the odor is less (as Mike Ware
has warned) does not prove the material *harmless*. In fact, pain to
nasal passages COULD be a useful warning, prof says -- glyoxal could
still jump into your DNA, just do it silently!
I gather that all safety data so far show glyoxal much the lesser evil,
and I can attest that it's a thousand times less disagreeable to use --
in fact quite comfortable -- perhaps all the more reason to be on guard.
Anyway and whichever, use it outdoors or with hood.