So I'm not sure if I am misunderstanding the terminology or if I am really missing something all together. As an experiment, i tried to get the ambient (air) temp up to 90ish degrees in an empty vision tank. I have a 75 watt ceramic heat lamp overhead with a piece of 11x24 flexwatt underneath. I set the thermostat to 91 degrees with the probe glued inside of the tank, directly on top of the flexwatt. Turned everything on and let it set for a few hours. The surface temp with newspaper as substrate was right at 90 degrees using a temp gun. The ambient temp in the reptile room is about 78 degrees and the ambient temp on the hot side of the tank was about 82 with a digital thermometer. So I tried to get the ambient temp up to 90ish on the hot side using the thermostat. I then put the thermostat higher and higher until I reached its max of 108. The surface temp went right to 108 but the ambient temp only went to 86. So I plugged the heaters directly into the wall and got the surface temp to about 124 and finally got an ambient temp around 90. So what am I missing here? Certainly not going to keep my snakes on a 124 degree surface!