Soy Wax Candle Forum - Online resource for soy candle makers

I have just started doing soy wax candles. I am very happy with the results. The smell is great, the look is cool, and they burn very well. My only questions is when my candles finish hardening after I pour them, they have a flakey look to the top of the candle. This does not seem to affect the functionality of the candle, but it still looks kind of bad. Even after I burn the candle, once the wax rehardens, it returns to a crumbley flakey look on the top of the candle. Any idea as to why this would happen, or how to prevent it?