Re: Pyro redevelopment & Hardening


FotoDave@aol.com
Thu, 28 Jan 1999 19:18:43 -0500 (EST)


In a message dated 1/28/99 4:06:46 PM Pacific Standard Time,
lawless@vignette.freeserve.co.uk writes:

> I don't know if glyoxal hardens as effectively as
> formaldehyde, but I do know that APH negs still need to be handled with
> great care even after hardening. Or maybe I'm just ham-fisted?

I read somewhere that although glyoxal is different from formaldehyde, it is
the same principle that the aldehyde that does the hardening, but I am not a
chemist.... :)

> What Dave says about hardeners reducing the solubility of gelatin is true,
> but it also makes it physically tougher - not a great deal, perhaps, but
> alt. negs are subjected to a lot of handling.

Yes, hardening is good, and I use hardening fixer too. I was just trying to
point out that the term "hardening" should not be thought of as truly
hardening something rock hard.

I think in general hardening is good. In fact, the point that Cor brought up
(about micro-organism) is important although I mentioned that it might not be
the primary reason for hardening the size. While most manufacturers claim that
the film is tough enough that they don't need extra hardening to protect them
from being scratched, there is still a need to harden the film to make them
physically tougher and not soluble especially if you live in a humid area. If
the gelatin swells because of humidity, then you basically have silver-
flavored JELLO which could invite insects.

Dave



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