+x KLComposites - 2/19/2019 2:09:22 PMI make wet-laid molds out of fiberglass, compensating for the reduced stiffness with extra thickness. The glass, being translucent when saturated, allows me to see any voids between the surface coat and the first several layers of reinforcement that need to be rolled out. Any air, no matter how small the bubble, will expand as its heated in the post-cure cycle and pop through the surface coat, leading to what you've described - burst pinholes and/or blisters.