Ok, This problem is reasonably common with highly polished molds. They actually are too smooth to get all the air removed. My first move would be to go to the auto parts store and get a spray bottle of TIRE WET. This is a product I use to make the acrylic glide on tools more easily and kill bubbling. If that doesn't work, and it almost always does, take your mold to a glass bad booth and frost it up.