To me, the mushrooming varies from fragrance to fragrance. I will get mushrooming with some FOs and not others. The amount of FO is another factor that will affect mushrooming. If you've been burning your candle for four hours, you can extinguish the flame, trim the wick and get rid of the mushroom. You can light your candle immediately thereafter. Be sure to remove any drippings from your pool of melted wax. I don't know anything about the "flowing air current" though. Sometimes the mushroom appears at the beginning, midway, near the end of the burn and sometimes not at all. I sure wish I could give a more definitive answer but as you know, there are no definite answers when it comes to candlemaking.