The candle cap acts as an air flow regulator which causes the candle to burn cleaner and more evenly while reducing soot.  Application of the Candle Cap to a new candle will result in a higher than normal flame that burns above the lid surface. Therefore, it is recommended that its use be delayed until the wax level has fallen one inch from the as-new level.  The Candle Cap does get hot while burning your candle, so make sure you let your candle cool down before touching or removing.