I'm trying to install a new kitchen garbage disposal and have arrived at the point where the existing flange in the sink must be removed. All the bolts are off but I can't get the flange to come out. I've tried banging on it from the bottom (first resort of the beginner!) and have tried getting a putty knife under the flange from the top (second beginner's step). The darned thing won't budge. As the sink is but a year old I don't want to damage it. Any suggestions will be greatly appreciated. There's the possibility that the plumber used silicone or some other sealant to close this thing tightly. Any ideas how to handle that possibility?