A Heat Pipe is basically a sealed copper-alloy tube filled with a thermally conductive gas mixture. The gas mixture is non-toxic. The device is designed so that when one end of the heat pipe is at a higher temperature than the other end, heat is rapidly and continuously transferred from the hotter end to the cooler end. Heat pipes are inherently more thermally conductive than copper. Heat pipes will heat or cool within their temperature ranges and are available with maximum operating temperatures up to 600ºF (316ºC) (for high-temperature, use the TPH-type heat pipe). Please note, if running water coolant in your mold, water coolant temperature should not exceed the regional boiling point of water (typically 100ºC or 212ºF, but may be lower at higher elevation).