Re: glyoxal v. formaldehyde

[Don Sweet <don@sweetlegal.co.nz>]

Thanks for explaining that.  I understand that if virtually all of the glut
permanently bonds with the size it has no remaining toxic potential (unlike
formaldehyde which is relatively inefficient at bonding).  An essential part
of the safe use of aldehydes must therefore be to use no more than
necessary; is that right?
Don Sweet

----- Original Message ----- 
From: "Ryuji Suzuki" <rs@silvergrain.org>
To: <alt-photo-process-l@usask.ca>; <don@sweetlegal.co.nz>
Sent: Tuesday, April 08, 2008 10:40 PM
Subject: Re: glyoxal v. formaldehyde


> From: Don Sweet <don@sweetlegal.co.nz>
> 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).
>
> --
> Ryuji Suzuki
> "The truth that I am seeking is in your missing file."
> (Bob Dylan, Something's Burning Baby, 1985)