[pure-silver] Re: Film developer temperatures??

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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