You mentioned boiling water in your original post.
Whatever, the LED bulb will not heat the water by nuch at all, as most the the energy is being used produced as light, while the filament bulb is producing more heat than light. If you want to set up some sort of convection in the bottle it will have to be a heat source. I really think you need to find an established design and follow their instructions.
( Bartleby A dead man on vacation, Wed 5 Sep 2012, 13:49, Reply)