Re: Help with what I believe is a hardening issue

From: Alberto Novo <alt-list@albertonovo.it>
Subject: Re: Help with what I believe is a hardening issue
Date: Tue, 16 Nov 2004 07:59:56 +0100

> I like complicated ways... if the destination is worth while.
> May you give me some details?

Don't get too excited... It's not that complicated here.
2,4-dichloro-6-hydroxy-s-triazine is just another hardening agent,
which was patented in 1960's, I think (I have the original patent
somewhere), so it's been known for some 40 years. Some people may
prefer this over glut because it is nonvolatile and works just as
well. This and similar compounds are often categorized "active halogen
hardener," "s-triazines" or something similar, and you can find
details in James's book. By the way, there seems another James but
when I say James I mean T. H. James, and when I say James's book, it's
The Theory of the Photographic Process, 4th edition.

Synthesizing a batch of this compound takes me a couple of hours, and
it takes overnight to purify the crude solution by recrystalization,
if purification is necessary. Its precursor is cyanuric acid (not to
be confused with cyanic acid), which is commonly traded as an
industrial intermediate material. Cyanuric acid itself can harden
gelatin but it is insoluble in water. A partial hydrolysis of cyanuric
acid 2,4-dichloro-6-hydroxy-s-triazine is soluble in water, and it
still maintains the parent compound's crosslinking ability, so this
compound is preferred to cyanuric acid.

I only do silver gelatin so I can't say about other processes, but
there seem to be a couple of people who are willing to test it when I
make another batch of it next time.

There are a few other popular hardening agents.
bis(vinylsulphonylmethyl)ether is another one.

--
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)