From: Jack Fulton (jfulton@itsa.ucsf.edu)
Date: 01/07/02-10:21:16 PM Z
Not to quibble here but it would be better to say that 'formalin' is
'formaldehyde' in the sense that 'formalin' 37% 'formaldehyde.'
Chrome alum can certainly be used as a hardener and it is used in some stop
bath formulae. Since Chromium is a known hazard . . here you might think of
the intensifier Mercuric Chloride to get an idea of the hazard of metals . .
. you might consider using Potassium Alum instead.
I don't know of any specific advantages of one over the other but since the
1960's (when I worked first w/color), formalin is used in many of the color
processes. Today, for instance, it is still used in the E6 process. However,
due to advanced chemistry, it is cleverly 'locked' in the Pre-Bleach rather
than in the Final Rinse so it won't "escape" into the atmosphere.
Formaldehyde is smart to use thought to harden emulsions for higher
temperature processing.
Jack Fulton
> << My question is, what are the relative advantages of formaldehyde versus
> formalin versus chrome alum? >>
>
> Clay,
>
> Formaldehyde is formalin. Its hardening is stronger than chrome alum and is
> instanteneous, but both can be used as I have used even food alum (the
> weakest).
>
>
> Dave S
>
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