Jobo CPE2 C-41 developer temperature consistency question

[Arthur Fleischmann]

I recently bought a used Jobo CPE2 processor which I have been using to process C-41 film. I mainly develop 5x4" film using the 2509n reels in a Multitank 2 tank.

Last time I processed film I measured the temperature of the developer immediately after it came out of the tank through the lift and the temperature had fallen to just a bit over 36 degrees C (from 37.8 when I poured it in). Is this normal, has anyone of you using a CPE2 (or CPA2, CPP2) processor ever measured the chemicals' temperature right after processing? My tempering bath has the right temperature (I even heated it to 38.3 degrees) and I pre-heated the tank for about 15 minutes before starting to process. My negatives look ok, though... :confused:

 

[Photo Engineer]

Arthur;

I always prewet my film, drum and reels with 100 F water before beginning the process. I set the temperature to about 0.1 degree F over 100F for this due to the evaporation induced temperature loss at the surface of the temperature bath and I have the developer at 100.1 F when I dump it in. The result is an exact 100 F for my conditions. I use 2 - 3 thermometers during a run to insure that the prewet, bath and developer are all at the right temp.

I should add thought that if your temperature is about 1/2 deg low or so, but is the same every time, you should get repeatable results even if it is just a slight bit low in speed and contrast.

PE

 

[Arthur Fleischmann]

Thanks, I omitted a pre-rinse so far because I read somewhere (can't find where at the moment) that when pre-wetting C-41 film this might result in colour shifts. But I shall try it, anyway. May I ask which processor and tank you use, PE? And for how long do you pre-wet the film?

 

[Photo Engineer]

I have both a CPE and a CPP. I use the same reels you do and the same jobo tanks with lift. I do roll film in the 1500 series tanks with reels, but the sheet film as you do. I run up to 12 sheets of 4x5 at one time with coupled 2000 series tanks.

I prewet the film for about 1 - 2 minutes, and the prewet has little effect on quality, if done right.

PE

 

[AgX]

An alternative to pre-wetting would be using an airflow of 38 C° through the drum by means of a modified hairdryer calibrated to that temperature.

 

[Arthur Fleischmann]

Thanks again, I will try pre-wetting and post the results here.

Hmmm... hairdryer! Interesting idea, but I wouldn't know how to calibrate it to the correct temperature.