glut again

From: "Christina Z. Anderson" <zphoto@montana.net>
Subject: Let's switch the New Orleans controversy to glut now please...
Date: Thu, 01 Sep 2005 19:44:48 -0600

> NOW, let's get back to some real controversy: glutaraldehyde.

I didn't know it was a real controversy... it is clearly the best
hardener I've used myself for plain gelatin. I've posted a bunch of
Dow Chemical's safety related links several months ago (like the one
Gord posted yesterday). One of the early player in commercial glut
production c. 1960 was Union Carbide Corporation. This is now a part
of Dow. So Dow has very good experience in this chemical, although
their user brochures are currently directed to health care providers
who use glut solution in open trays. (I don't recommend to use glut in
open trays for photographic purposes, unless you have a good fume
hood, other means of good ventilation and proper lab safety training.)

(For educational applications and some special applications,
bisepoxides are another class of excellent hardeners, which is just as
effective as glut, with no fume and odor, but the sized paper should
be aged a week before further coating. I wetted epox hardened paper
and glut hardened paper and did some tests, but I couldn't visually
distinguish the two. Also, a mixture of glut and epox worked very
well.)

From: Don <dstevenbryant@mindspring.com>
Subject: RE: Let's switch the New Orleans controversy to glut now please...
Date: Thu, 01 Sep 2005 23:25:04 -0400

> I thought I might write that the batch of Rives BFK that I gave you
> samples of was sized as you mentioned above but also had baking soda
> added (per C. James recommendation.) I suppose the addition of the
> baking soda is to promote hardening (that cross linking thing I
> guess) but it also may have added to the gritty feeling of the
> paper.

Glyoxal works as a hardener but in a narrower window of pH compared to
glut. Glyoxal is effective in pH above 8 or so, while glut can harden
at pH as low as 4. Of course, glut becomes more effective at a higher
pH, but at any pH, glut is far more efficient as a hardener. Also, it
is unnecessary to add an alkaline agent to bring the pH up for the
hardening purpose.

It is my impression that many silver and non-silver processes work
best when the paper is at low pH, so glut is advantageous here as
well. (Chris's glut hardener is adjusted to pH of about 4. The pH will
go up a bit when mixed with gelatin solution.)

> God willing I will attempt to size some FEW with glut in the following days
> since the sweltering heat wave seems to be abating and I've put up a drying
> line in my garage.

Let me know what you find with the white cap and the blue cap vials.
One of them is identical to what Chris has been using, and another is
different formulation but supposed to work very similarly. If your
test result is good, and if there's enough demand, I'll work out with
a company so that people can buy glut for hardening off the web easily.

Ryuji
Received on Fri Sep 2 00:15:15 2005