Re: glutaraldehyde

From: "T. E. Andersen" <postlister@microscopica.com>
Subject: Re: glutaraldehyde
Date: Wed, 17 Mar 2004 15:41:18 +0100

> No, I see no reason for the glutaraldehyde to be better. It causes a
> much higher degree of crosslinking of the proteins in the gelatin. This
> is often of value in microscopy, but I don't see how this could be
> beneficial for hardening alt-photo paper.

Increased crosslinking is very beneficial in hardening gelatin. It
makes gelatin more durable during wet processing, and commercial
photographic films, paper, and other non-photographic printing papers
where gelatin size is used, are hardened with glutaraldehyde, often
with some other non-aldehyde hardeners to achieve very strong
hardening effect.

> On the other hand, it may well
> prove to reduce the archival properties of the coating. I do not know
> this to be the case, but I would not be surpriced if it did. After all,
> the more cross-linked the proteins are, the more brittle the gelatin
> will be, and the less of the protein molecules will be free to adhere to
> the paper and image layers. Again, I do not know this to be a problem,
> but it's fair assumption.

I suggest you study literature before making such a speculative
comment. Hardening of gelatin have little influence on mechanical
properties of dry gelatin. Also note that gelatin is degraded collagen
product and is a bit different from proteins you are accustomed to.

> I have not used glyoxal (HOCCOH) yet (but I've bought a bottle to test).
> It's similar to glutar aldehyde (HOC(CH2)3COH) in being a dialdehyde, so
> it too, is cross-linking.

Glutaraldehyde is superior cross linking agent to glyoxal and
formaldehyde because GTA is bifunctional, meaning that it can attach
to two separate gelatin molecules. I suggest you study literature
before making speculative comments here, again.

--
Ryuji Suzuki
"All the truth in the world adds up to one big lie." (Bob Dylan 2000)