Place the candle or candles directly under the metal bolt and washers. That way, the tip of the candle flame is about an inch under the bolt. The hottest point on a small flame is immediately above the blaze itself. The nut, bolt, and washers will turn red after not very long. The heat then radiates to the terracotta surface of the first and outer pots. The entire large surface of the outer pot becomes very warm in no time! And all from a tiny little candle flame. The surface gets around 200 degrees on average, so protect yourself from burns and don't let the little ones around it unattended. It is critical to know that if an emergency cold weather event happens where this device helps for survival, place it in the smallest room possible! Or, you won't feel much temperature change. Aside from choosing the smallest room, block all cracks where heat may escape to conserve warmth.