You are correct that developing agents respond differently to temperature. For example, hydroquinone loses activity rapidly below 18 C and becomes essentially inert below 13 C. Above 27 C it tends to produce fog. Certainly, a degree change or two is not going to make much difference in the character of the negatives produced by developers containing two or more developing agents. However, if you decided to change your developing temperature from 20 C to 24 C some testing might be adviseable. Developers are *usually* complex mixtures and there are many different processes going on during development. Each process will react differently to temperature changes and may effect the final result. Jerry -----Original Message----- From: pure-silver-bounce@xxxxxxxxxxxxx [mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of john stockdale Sent: Sunday, March 20, 2005 6:40 PM To: pure-silver@xxxxxxxxxxxxx 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=20 >excessive swelling of the rather soft emulsions of film and paper of=20 >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=20 >to see if they withstand higher processing temperatures but all should=20 >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=20 65degF compared to 68degF. Maybe because it's a highly alkaline developer=20 which might cause emulsion swelling more than most others? Also, do not some developing agents respond to higher temps more than=20 others, so that in a 2 agent developer like metol-hydroquinone the=20 hydroquinone has a proportionally greater effect at higher temps? =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there. ============================================================================================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.