Re: glyoxal v. formaldehyde
From: Don Sweet <firstname.lastname@example.org>
Subject: Re: glyoxal v. formaldehyde
Date: Tue, 08 Apr 2008 17:09:38 +1200
> 1. Is it not important to be aware that glutaraldehyde is
> much more toxic than formaldehyde in terms (for example) of
> a splash in the eyes?
The reality is that the glutaraldehyde is used in much smaller
quantity and this differences outweigh the small difference in
the toxicity data. Also, the published toxicity data should be
interpreted with the dosage levels and effects they caused.
> 2. (Even more naively perhaps) if f'de will outgas at room
> temperature but g'de will not, what implications does that
> have in terms of the comparative residual toxicities of the
> hardened size on prints?
Glut is used in such a small quantity because majority of the
glut will permanently engage in the hardening reaction. Only a
small fraction of glut will vaporize. On the other hand, the
commonly reported amounts of formaldehyde and glyoxal in
sizing solution are huge. Suppose 20ml of 40% solution is
added to a liter of warm water containing 30g gelatin, this is
8g formaldehyde in 30g gelatin. This is 27%
hardener-to-gelatin ratio. I'm nothing like Steve Jobs but
this is HUGE. Less than about 10% of that quantity (1 to 3% of
gelatin weight) is actually needed for hardening reaction, and
the rest is excess. But such an excess is needed because
formaldehyde's hardening is slower and less efficient than
glutaraldehyde reaction. If you used glut, you would only need
about 0.5 to a a couple of percents glut (in relation to the
gelatin content, not water).
"The truth that I am seeking is in your missing file."
(Bob Dylan, Something's Burning Baby, 1985)