developer temperature

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What is the effect exactly of changing the developer temperature much above the recomended (&compesating with shortening the development times)? It seems that there is no consensus regarding this point. Some say that there is no difference with newer developers, however with older ones the developer may act totally different in different developers?

-- xosni (xosni@gega.net), March 27, 2001

Answers

With moderate temperatures, the usually-recommended 65F to 75F, the most prominent effect will be increased graininess near the low and high end of that range.

Developers and films react to temperature changes slightly differently in regards to time changes to match a specific CI; ideally you'd run tests at various temperatures to learn exactly what times result in matching CIs. A calculated compensated time may be so close to what's needed there'll be no significant difference, but otoh it may be quite a bit off. Generally speaking, though, the calculated time will be close enough.

See _Controls in Black and White Photography_ by Dr. Richard J. Henry for more than you ever wanted to know about this.

-- John Hicks (jbh@magicnet.net), March 28, 2001.


A general rule-of-thunb is that chemical reactions double in activity for every 10 degrees Celsius rise in temperature. Most published time-temperature charts simply reflect this, and show a straight line nomograph.
What these charts don't take into account is that there is a slight difference in the reaction of the various developing agents to temperature change. Developers using only one reducing agent will behave fairly consistently over a wide range of temperature, but those with two or more, such as common M-Q and P-Q formulations won't.
What happens, in effect, is that the proportions of the developing agents shift out of balance away from the design temperature of the developer: Change the temperature, and you're effectively using a different formula.

It's best to stick close to the manufacturer's recommended figure, unless maintaining that temperature is a real problem. In that case, you're on your own, and your particular use of 'Micropanatol-Z' won't give the result that the designer intended.

-- Pete Andrews (p.l.andrews@bham.ac.uk), March 28, 2001.


Xosni:

Years ago Kodak used to publish different time:temp nomographs for different film:dev combinations. The slopes of the lines were oftentimes different, thereby indicating that different film:dev combinations reacted differently to temp changes. The slopes used to oftentimes be different for a particular developer at different dilutions. Today we tend to use the same time:temp chart for all film:dev:dilution combinations. Maybe that's because the differences aren't excessive, or, maybe Kodak and Ilford and the rest figure they can just leave it up to us to figure out.

-- Ken Burns (kenburns@twave.net), March 28, 2001.


So temperature & time are not reciprocal, right? I do develop in high temperature during the summer (30ºC - I live in Cairo- egypt) I don't realy see a tangible difference.

-- xosni (xosni@gega.net), March 28, 2001.

I live in Texas and often process as high as 80 degrees F. in the summer (usually with PMK). I notice slightly more base fog at higher temperatures, but otherwise don't seem to have a problem with the development. I do know that some developing agents respond differently to temperature changes--paraminophenol hydrochloride (the agent in Rodinal) is much less sensitive to temperature changes than most other known agents.

-- Ed Buffaloe (edb@unblinkingeye.com), March 29, 2001.


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