From: Judy Seigel (jseigel@panix.com)
Date: 03/14/02-01:17:29 AM Z
On Wed, 13 Mar 2002, Tom Ferguson wrote:
> How long can a sealed bottle of 40% glyoxal be kept? Its intended use is
> hardener for gelatin for gum prints.
Tom, tho I find the life of the working solution is brief, in my
experience the stock solution keeps well... and unopened I would expect to
keep for years. There are two ways of testing in my experience (this is
purely by practice, I have no higher authority on the matter).
I do a first guess at the working solution by smell. When it's still fine,
on the first day, it has a *faint* odor similar to formaldehyde. When that
odor is gone, I discard working solution.
So far, any stock solution (from the bottle) I've poured has still had the
odor (remember, it's faint -- and if you've smoking, or otherwise abusing
your faculties, might not notice !), even from half-full bottle which sat
for a year or more. And has always worked... But I've also tested the
hardened against unhardened & difference is very clear. If you're uneasy,
do a couple of 21-step prints, one on the gelatined paper with no
hardener, the other with the paper hardened in the suspect glyoxal...
The difference is quite apparent. And if it isn't working, you can always
reharden.
Incidentally, I time the hardener... finding no improvement after 5
minutes, but less than 2 min. risky.
Of course as we know these variables vary at will... so no guarantees. But
... I don't THINK you'll have a problem. (I trust you'll not keep us in
suspense.)
best,
Judy
> I just found an unopened bottle (still in its sandwich bag) from ??? at the
> back of my closet. I am under the impression (don't know from where) that
> glyoxal goes bad over time. Other than testing/printing on paper, is there a
> way to tell good from old/bad glyoxal?
> --
> Tom Ferguson
> http://www.ferguson-photo-design.com
>
>
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