From: Judy Seigel (jseigel@panix.com)
Date: 12/06/01-01:20:33 PM Z
On Thu, 6 Dec 2001, Ted Edkins wrote:
> Judy, glyoxal should keep better at a lower temperature than room temp so a
> frig is useful. Another possibility is to add some sodium bicarbonate to
> reduce the acidity. Add the sod bicarb until the fizzing stops.
>
The bicarbs do it the least, but alkali tends to turn the glyoxal orange
(for BRIGHT orange try sodium carbonate). I found 1/2 tsp carbonate of
soda was the maximum per litre before bad color change, and gave it up
because I was always a little antsy about that. I wasn't doing it to
*preserve* the glyoxal, rather in the belief that the bonds of the gelatin
are strengthened by the alkali in hardener (as told to me by a chemist,
though that's a hard one to test & I didn't).
My pH meter is non useful (some complicated calibrating solutions I never
got the hang of), but the idea that alkali could extend life of the
glyoxal is interesting -- I'll put it on the list ! Unfortunately, I've
found the only way to actually test if the glyoxal is still good, is to
make a print... and that also gets to be more drawn out than seems worth
it, at least on a regular basis.
My rule of thumb has been, does it still have characteristic odor? But
all things considered (including the state of my refrigerator) it's more
*economical* to plan the hardening as a batch, & then throw the stuff out.
(I use 15 cc stock glyoxal per litre of hardener solution -- if 500 cc of
the stuff costs $30 delivered... that's what, about 75 cents per litre? )
However, on the 3rd hand -- if you have a handier way to TEST the glyoxal
without having to actually print the emulsion on the paper (and always
with a known strip for control !), THAT would be splendid...! ?????
Hopefully.....
Judy
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