Make sure the entire top layer of the candle wax liquefies before it is extinguished, about 2-3 hours depending on the size of the candle. If you notice the candle burning unevenly, rotate it a quarter or half turn. Once there is an even pool of melted wax on the candle, you can extinguish it or let it continue to burn.
If the candle isn't burned long enough the first time, only a small diameter of wax will have melted around the wick. Since next burn cycle mimics the first burn’s diameter, the wax will start "tunneling" and melt downward. When this happens, only a portion of the wax in the candle will be consumed, thus reducing its burn time.
To care for an ILLUME candle between use, trim the wick of an ILLUME candle -- about 1/4” each time -- before you light it. This will help prolong the life of the candle and to prevent sooting.
When an ILLUME candle is completed, the candle will self-extinguish courtesy of its safety wick tab. The tab also prevents relighting, and the remaining wax serves as a safety measure since it helps secure the tab.