Why shouldn foreign matter (bits of matches, pieces of wick, flies and other insects) ever be in the liquid wax?
The foreign matter can soak up wax and catch fire; it thus acts as a second wick, causing the candle to disintegrate and thus become a hazard. This is especially true when the foreign matter is at the edge of the candle. In pillar candles the edge can be breached and the candle keeps on running and will ‘waterfall’ off the side and puddle onto what is at the base, hopefully a candle base. In jar candles, if the burning material floats over to the side of the glass it can cause the jar glass to shatter. Tiny foreign particles (dust) can clog the wick. As a result, the wick cannot absorb the liquid wax any more and peters out. This also happens with low quality pigments and dyes.
