There are a couple ways to prevent air lock when using a phunnel / funnel bowl. The first way to prevent air-lock is to get a good foiling technique down. I have found that a piece of foil that is 6-8in long and 6in wide is the ideal size to work with. Another way to combat air-lock is to poke holes in the foil over the spire. If you employ both of my methods, I can assure you that you will have a successful smeesh.