Re: Help with what I believe is a hardening issue

From: Ryuji Suzuki ^lt;>
Date: 11/12/04-12:33:53 AM Z
Message-id: <>

From: "T. E. Andersen" <>
Subject: Re: Help with what I believe is a hardening issue
Date: Wed, 10 Nov 2004 15:33:15 +0100

> The oxidation should be very minimal due to the methanol added to
> commercial formalin. As much as 15% is added to prevent/ reduce the
> oxidative formation of the formic acid and/or disproportionation
> (not sure that's the correct english term.

I don't use formaldehyde or glyoxal as a photographic hardener, but we
prepare formaldehyde solution by dissolving paraformaldehyde, because
people use it for electron microscopy as well. I know methanol
somewhat prolongs shelf life and suppress polymerization as well, but
I am not sure if that's all that effective, especially when metal
impurity level is unknown. I you can say "by the principle of Le
Chaterier" for that. The term appears in first year college chemistry
textbooks. (it was on a highschool textbook in Japan but that was
years ago.)

> Btw. formaldehyde
> should be kept at room temperature, as keeping it in the fridge
> accelerates the polymerization into paraformaldehyde.

I think formaldehyde sans methanol is better kept
refrigerated... though it would last only for a couple of weeks

> The paraformaldehyde may be redissolved by adding sodium hydroxide and
> heating to 70*C. This is, however DEFINITELY NOT RECCOMMENDED, unless
> you have a fume hood, and are skilled in laboratory practices.


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)
Received on Fri Nov 12 02:36:40 2004

This archive was generated by hypermail 2.1.8 : 12/08/04-10:51:33 AM Z CST