[rollei_list] Re: OT: development

Richard

I remember on certain films we used a formalin bath
to harden the very soft emulsion.  As I recall, it was
on some sheet films.  This was in the 1940's.  The
darkroom smelled like a mortuary!

Jerry

Richard Knoppow wrote:

> ----- Original Message -----
> From: "Allen Zak" <azak@xxxxxxxxxxxxxxx>
> To: <rollei_list@xxxxxxxxxxxxx>
> Sent: Friday, May 20, 2005 8:36 PM
> Subject: [rollei_list] Re: OT: development
>
> > In 50 years of photography I have not once experienced
> > emulsion damage
> > from using non-hardening fixers.
> >
> > Allen Zak
> >
>   I doubt if many if any current materials need hardener.
>   The standard hardening fixing baths like Kodak F-5
> (essentially the packaged Kodak fixer) originated in the
> mid-1930s when emulsions were very soft compared to modern
> materials. In fact, up to about 1939 the standard processing
> temperature was 65F. It was raised to 68F after that because
> some method of improving hardening was applied. I think we
> use hardening fixer mostly because of tradition.
>    Auxilliary hardener is included in some color processes
> which operate at very high temperatures and are necessary
> for some special processes like monobaths, which are very
> high in pH, but I agree that in general one could do without
> hardener  and suffer no consequences.
>    OTOH, if a wash aid is used the hardener does no harm and
> may cause film to dry faster (less absorbed moisture due to
> less swelling).
>
> ---
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@xxxxxxxxxxxxx
>
> ---
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