The safest heat to use is UT (under tank) heating, but if you don't electronically control the heat, the use of paper towels or newsprint as a substrate could very well kill your snake. I find the cheapest rheostat to use is aspen bedding. You increase or decrease the substrate depth until you achieve a safe temperature INSIDE the warm-side hide of the cage (80-85F.). The cool side should be cooler than 80.
Paper towels and newsprint are fine if you heat the entire room to digesting temperatures or if you use a theromostat or rheostat to control the heater. Since most of the readers of this forum do not use either, I recommend you use only aspen bedding as a substrate. It's chemically benign and absorbs and desiccates liquids rapidly. No worries about the snake burning itself on the UT heater since (unlike ball pythons) most corns have the sense to distance themselves from the hot cage bottom. Be sure the UT heater is under only one end of the cage so the snake can retreat to the cool end of the cage when necessary. Hides at both ends of the cage are recommended to facilitate thermoregulation (beneficial to digestion and shedding).
Don
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South Mountain Reptiles