Re: Glutaraldehyde: a different kind of cautionary tale

Hi folks,
In the process of writing my web page on the chemistry of the gum
process, I've gotten into the chemistry of the leather tanning
industry. In the process of exploring this sidetrack, I've discovered
and perused the archives of two online discussion forums devoted
entirely to the chemistry of leather tanning, sponsored by industry
groups.

One thing I've learned in reading these forums is that
glutaraldehyde-tanned leathers don't age well; within 6 to 12 months the
leather turns yellow, and soon after turning yellow it loses its
strength and integrity and can be torn as easily as paper. For this
reason, glutaraldehyde isn't recommended for the primary tanning process
for leather. It is sometimes used to add perspiration resistance to
leather intended to be worn next to the skin, like cushioning for
prosthetic devices for example, but in these cases it is recommended
that the glutaraldehyde be used as a post-treatment for leather that has
first been tanned with chrome or some other tanning agent and thus
rendered safe against the weakening effect that glutaraldehyde has when
used to tan raw (pickled) collagen.

I don't have any idea whether this information has any relevance to
gelatin hardening for alt-photo purposes. I'm arguing in my website
essay that the chrome-tanning model may not be a useful model for
photography involving dichromated colloids, but that's a different
issue. The fact that Ryujii uses glutaraldehyde in his work to harden
gelatin with apparently no such result suggests that it may not be
relevant; there may be something different about how glutaraldehyde
works on collagen vs how it works on gelatin, or more likely IMO
something in the tanning process itself (perhaps something in the
pickling liquors; the tanning process is incredibly complex and uses a
witch's brew of different liquors and salts and whatnot) that creates
this effect. At any rate, I found it interesting in the context of
discussions here about whether glutaraldehyde should be adopted as the
chemical of choice for hardening gelating sizing, and thought I'd throw
it in for whatever it's worth, which may be nothing at all. At ease,
  

Katharine Thayer
Received on Wed Apr 28 22:57:59 2004