Interlux 601 Fiberglass Surface Prep Interlux Fiberglass Surface Prep is a mold release agent and wax remover, which precludes the need for sanding bare fiberglass when used with Fiberglass No Sand Primer. It is also used to thoroughly clean the gelcoat and provide a key for the Fiberglass No Sand Primer to be applied. The use of Fiberglass Surface Prep to remove these contaminants is extremely important if full adhesive qualities of Fiberglass No Sand Primer are to be realized. Fiberglass Surfa