I had a buddy show me this trick. I tried it and it works great. The large boil bubbles break up into tiny bubbles, no foam over. Anyone else tried or heard of this trick?
I have one in my kettle too for keeping the hops out of my fermenter, and it works great. I've still had boilovers though so it doesn't work that great to stop that from happening, but I'm sure it helps some. I've only had boilovers when I cover or partially cover the kettle, when wide open I've never had a problem. I usually do 10gal batches in a converted keg.