I found that I cold contact print Tri-X developed in HC-110 using a Zone VI cold light with exposures in the 30-45 second range with the head very near the paper. When I switched to TMY developed in Pyrocat-HD the exposures increased to 120 seconds. I found that to be too long and switched to a different light source. I obtained one of the Azo "Cold One" heads and now my times are 9 seconds, with the head at the top of the enlarger! Note: all times quoted are without a lens.