If you’re a tray developer, this might raise your temperature

[mandoman7]

Its not just trays that have the problem of drifting temperature during development. Daylight tanks will drift, along with anything else that's not in a controlled bath. I found the answer to be a matter of checking at the end of processing, if the air temperature is different than the processing temp (or warm hands are in the solution). If there's much wander, the median temperature is a fairly reliable reference point for your development time, although I still always use larger trays for temperature restraining out of habit.

[Brian Ellis]

I used the BTZS tubes for many years to develop film. The tubes were in a water jacket and obviously my hands never touched the developer (though they did touch the tubes as I rotated them in the water jacket). I had an air conditioning system that kept the darkroom around 70 degrees and in Florida heating the darkroom was unnecessary. I started out with water in the water jacket at two degrees below the developer temperature. I put ice cubes in the water jacket to keep the water temperature from increasing. I didn't measure humidity but I'd assume it was pretty low because of the air conditioning unit. Nevertheless, despite all of these efforts in the course of about 8 minutes development time on average the temperature of the developer at the end was always about 2 degrees warmer than when I started. Fortunately this increase was consistent so it was factored into my tested times for normal, plus, and minus development.

I used the Zone VI compensating developing timer for prints but not for film except when I used to tray develop 8x10 film. Zone VI Studios said it could be used with film in tanks or tubes by using the timer to measure the temperature of the water in a water jacket. I was never sufficiently confident that the water temperature translated to the developer temperature accurately and consistently enough to try it.

[Curt Palm]

Full disclosure: I wrote and sell the CompnTemp software

CompnTemp is a software version of a compensating developing timer. It uses a USB temperature probe. It offers several improvements over the zoneVI timer.

-Displays the current temperature. (F or C)
-User can set the target temperature.
-both real time and compensated time are displayed.
-custom compensation curves can be added and used.
-countdown or count up timer modes.
-customizable interval tone