The mold surface affects three important areas of the molding process. First, the quality of the mold's cosmetic finish will be reproduced in every part. Regardless of whether it affects the physical performance of the part, every customer will judge your work by the surface quality. It is much easier to perform the steps one time on the mold surface than to touch-up every part after it is finished. Second, the mold surface affects the release characteristics of the mold.
Any imperfections can contribute to adhesion problems.
When a part sticks in a mold, extreme measures are often used to force the release. These can lead to broken flanges and mold edges, gouges on the surface itself, and destroyed parts or molds. Finally, the mold surface coat is the protective barrier to the rest of the mold. Just as boats and other fiberglass structures can deteriorate due to exposure, a porous mold surface permits water, chemicals or other harmful agents to enter into the structural laminae below. For these three reasons, all molds will benefit from the procedures described below.