I was burning a black spell candle for charging and attuning my amethyst, and so much happened that I had to write it down in my journal! First, the flame was really large and strong for most of the spell, only coming down to a normal size when the candle was almost finished burning. There were also a lot of sparks near the base of the flame.
The wick also writhed and changed its orientation a lot, even seeming to fork into three tips towards the end! Plus, I think an ember fell off the tip, causing a chunk of wax to fall down onto the holder. It kind of formed a rippled ball at the base of the candle, and when it burned down, that wax ball melted and filled part of the relief carved into it!
The black wax flowing in-between the silver stars was really beautiful. And when the wick burned down, the fire refused to go out for about ten minutes, before it suddenly just started to fade away. It flickered a little bit, then kind of just reduced to an indigo glow in the bottom of the holder, before disappearing with a thin little plume of smoke.
Magic is awesome! I just wish I knew what all these signs could mean.