hardening gelatin with glutaraldehyde for sizing (was Re: report on glyoxal yellowing)

From: "Christina Z. Anderson" <zphoto@bellsouth.net>
Subject: Re: report on glyoxal yellowing
Date: Sun, 14 Nov 2004 08:43:13 -0500

> Yesterday I emailed Don B offlist a comparison of gly hardened and glut
> hardened paper printed with the same neg and time of a cyano. It is amazing
> the difference. The cyano is sharp and navy and beautiful on glut, and dull
> and paler on gly. Now, this can be due to allllll kinds of variables, but
> what is hilarious is the fact that I didn't know this was the reason while I
> was developing.

It is possible that the surface texture and other more fundamental
difference is related to the difference you observed, but let me point
one thing here... The glutaraldehyde solution you have is weakly
buffered to slightly acidic pH, while I suppose you used glyoxal
without buffering or with an alkaline agent. This may have influence
on its own as well, and you might want to be careful if your interest
is to identify the variables that influences the "intensity" of cyano.

Glutaraldehyde works as a hardener in much wider range of pH than
formaldehyde and glyoxal and, this is indeed another advantage of
glut over other aldehydes.

Potential harm of glut is comparable to gly and form at worst. One
needs to factor in how small a quantity is necessary to harden gelatin
with glut compared to gly. Toxicity of a substance is determined by
how you are exposed to how much of the substance, not by number of
warnings found on the internet or number of votes on this list.

I personally don't want to be a chemical broker, but depending on how
many people on the list are neutral about glut (not sour or bitter),
there may be something that can work out. Also, if a real chemical
broker wishing to make a glut based hardener solution, I may be able
to help. But here's general info. Glut is usually supplied in 10%, 25%
and other strong solution, without pH buffering. As a hardener
solution, a concentration like 1% or 2.5% is more suitable. Use
minimal amount of very weak acidic buffer that does not interfare with
most processes, like acetate buffer to adjust the pH to 4 to 5, so
that the stock solution has long shelf life. If a particular process
dislikes slightly acidic environment, this can be reversed by adding
carbonate or whatever at the time of use, but caution should be used
because this makes the hardening effect much more rapid. If you don't
want to mess with this, some of the medical sterilizing solutions that
contain glut are pretty much acid buffered 2.5% glut with some
corrosion inhibitor, so they can be used as is. But they come in a
gallon jug or something big, though 100ml or 250ml can go a very long
way. So there's some need for brokerage here.

> And speaking of sizing: gesso was always gritty for me; hated it.
> Glut is smooth as a baby's butt. Glyoxal is gritty, too.

Thanks for the comment - I guess I'll look for smooth, nongritty,
cross-linkable clear acrylic polymers that can be used...

--
Ryuji Suzuki
"You have to realize that junk is not the problem in and of itself.
Junk is the symptom, not the problem."
(Bob Dylan 1971; source: No Direction Home by Robert Shelton)