Originally Posted by natewv
So then what is the advantage of the stopper using BM's method?
It keeps the contents of the bottle under pressure while you're filling, thus further reducing foam. that's why you have to poke the side of the stopper to keep it going, because the pressure inside the bottle gets to where the beer will stop flowing. I have used my BMBF with and without a stopper, and it definitely foams less with the stopper. When I didn't use the stopper before, my fill level ended up a bit low once everything settled because of the extra foam.