Re: Gum print formaline

From: maria ahlberg <mariaahlberg13@hotmail.com>
Subject: Gum print formaline
Date: Wed, 19 Jan 2005 07:52:53 +0000

> i am thinking of if there is anything else than formaline that you
> can use for holding the gum solution fresh.

There is a long list of compounds for this purpose. sodium salt of
2-phenylphenol (Preventol ON Extra flakes), thymol, phenol,
p-chloro-m-cresol, methyl p-hydroxy-benzoate, pentachlorophenol, etc.
I recommend Preventol ON Extra flakes for preservation of darkroom
chemistry, as it is very effective and is among the least toxic of
this sort of compounds.

> Can i use something else, less toxic?

Hardening agents in general are very reactive and capable of
crosslinking gelain macromolecules. So, they are all harmful by
definition. The difference is that some agents are more effective and
can be used in much smaller quantity. Some agents are nonvolatile, and
those are much easier to handle, especially in open tray processing.

I've done quite a bit of literature research and my own experiments as
well. Glutaraldehyde is the easiest and most effective hardening
agent. This is followed by 2,4-dichloro-6-hydroxy-s-triazine, active
vinyl compounds, epoxides, aldehyde starch, mucochloric acid, etc,
etc. Unfortunately, some of these compounds are not commonly
available. There are a couple of naturally occuring compounds capable
of crosslinking gelatin but those are supplied as pharmacological
agents and the cost is prohibitive for photographic use.

I think I've done enough community service in this area. Unless I get
a grant specific for this issue or something, I'll stick with
glutaraldehyde (and 2,4-dichloro-6-hydroxy-s-triazine, which is not
commercially available, but if you have a fume hood, you can make it
in a couple of hours.).

--
Ryuji Suzuki
"People seldom do what they believe in.  They do what is convenient,
then repent." (Bob Dylan, Brownsville Girl, 1986)