[pure-silver] Re: Film developer temperatures??
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Sun, 20 Mar 2005 15:02:11 -0800
----- Original Message -----
From: "john stockdale" <j.sto@xxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Sunday, March 20, 2005 3:40 PM
Subject: [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?
>
>
The swelling caused by the high pH of Rodinal depends on
the film. The same changes in emulsions that result in their
ability to work at higher temperatures make them less
sensitive to this swelling and the grain clumping that
accompanies it.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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