[pure-silver] Re: Film developer temperatures??
- From: john stockdale <j.sto@xxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Mon, 21 Mar 2005 09:40:14 +1000
At 08:32 AM 21/03/2005, Richard wrote:
... 68F became the standard temperature around the late
>1930's. Before that it was 65F! The reason was simply to
>prevent excessive swelling of the rather soft emulsions of
>film and paper of the time. Color film is designed for
>processing at 100F and much modern B&W film is made the same
>way. I would check samples of unknown films to see if they
>withstand higher processing temperatures but all should be
>OK at 70F or even 75F. Processing times are shortened. Kodak
>gives 75F as the preferred temperature for T-Max developers.
>I don't know why. Higher temperatures than 68F are often
>recommended for developers like Microdol-X, Perceptol, D-25,
>mainly because they are very slow. D-25 BTW is a good hot
>weather developer because it contains a lot of salts and is
>about neutral pH, both of which tend to minimise emulsion
>swelling. Its also slow so the increased temperature will
>not result in excessively short developing times.
I did read somewhere on the web that Rodinal actually works better at
65degF compared to 68degF. Maybe because it's a highly alkaline developer
which might cause emulsion swelling more than most others?
Also, do not some developing agents respond to higher temps more than
others, so that in a 2 agent developer like metol-hydroquinone the
hydroquinone has a proportionally greater effect at higher temps?
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