I made one yesterday. Its amazing. All the effects the drip of the candle can do. I want to get multi coloured wax and see the effect then. You should try it. Stick an average sized candle into the top of the bottle and burn it for a few hours. Make sure the bottle looks pretty.=]
I remember making one in the 70's. I think i took the label off, and it was a dark green bottle. I used different colored candles each time. It turned out very cool looking!