The Thermochromic banger has a special color changing yellow sand inside.
You heat the banger like any other banger you have used and you will see the yellow sand start changing color to orange then red. You find the temp that works for you by deciding what color works best for you. If you already know you like a banger at 700 degrees use a non contact infrared thermometer to scan the banger until you reach that desired temp, and take note of the color. Then you won't need to use the thermometer anymore. Just heat till you reach your desired color.
The sand will gradually return to a bright yellow when cool.