Hi Sinar - I would reccomend a Zone VI Compensating Development Timer. This device has a thermistor in a probe that goes into the print development or film development tray (or tank). As the temperature increases the timer slows down - or, as temperature decreased the timer speeds up. This thermistor circuit is proportional to the time/temp curve of the paper or film. It has a switch "Film" or "Paper" that can be set. Benefit: don't have to maintain a constant temperature. Check our Calumet site: http://www.calumetphoto.com/ctl?&ac....6;023;485;533;
Goog Luck with your darkroom.