WITCHES,Crackling flames during spells?

I'm aware that having crackling flames during spells means that spirits are helping or are there, but what about if you're doing spells that DON'T require you to call out anything? what does it mean if the flames start crackling? as i have had this happen to some of my candles during spells and NO they were NOT near any draft or had any dirt or any oils or any herbs inside..thanks...