I've been processing my own film for sometime now, and I've been using 72 degrees as my standard processing temperature. I use tanks with hangers for my 4x5 black and white. What I do is fill a plastc container with very hot water, and then put each tank (dev, stop, and fix) into this container to heat them up. Since my basement room temperature is 60 degrees this warms up the solutions. I usually warm them up until they hit 75 degrees, then I turn off the lights and unload the film, assuming that by the time I unload the film onto the hangers that the solution will be appoximantley 72 degrees. I don't think that this method is totally reliable. There has to be a way to maintain a constant 72 degrees during processing. That is my first question. My second question is: is the developer the only solution that is very temperature critical? The stop bath and fix don't have to be exactly 72 degrees, do they? Mine is usually between 70-75. Same for the rinse. Thanks alot!