Why do I get buildup and sticking in non-skid areas of the mold?

By taking a few precautions, you can achieve the same production from these types of surfaces as from a polished smooth surface. Buildup in non-skid areas generally can be seen as the same color as the spray-up gel coat. The cause of buildup in the grooves of the pattern usually result from either: 1) failure to apply the release into the tips of deep recesses in the pattern which causes small bits of gel coat or resin to bond in the tips with each cycle, or 2) excess release agent pooling in these areas because of poor application technique. When excess release is present, it does not have a chance to dry or cure thoroughly, or to develop full chemical resistance. The release films over on the surface and can attract free styrene from the gel coat or resin used to mold parts. This can occur because styrene in the resin acts as a solvent, penetrating the heavier areas of release and accelerating the buildup and sticking in these areas. To reduce the buildup and sticking concerns, care should be taken to thoroughly brush out and polish the release into these deep patterns without leaving a heavy residue.