What make bubbles surrounded by mig weld? ...
Answers: paint, grease, rust or other contaminants could cause porosity, also if interweave blows away your shield gas, or you are perhaps holding the nozzle too far away from your arc.
emmett: it's not a cooling gas, it's a shielding gas. it keep oxygen away from the molten metal, just similar to the coating on a welding rod. too much bake won't cause it- most production services run a MIG unit as hot as it will travel.
Not enough cooling gas , or to much boil.