Pettit Bottom Prep Fiberglass Dewaxer Pettit Fiberglass Dewaxer is a special blend of solvents, formulated to cut through and remove mold release, grease, and previously applied waxes from the gelcoat. Can be used above and below the waterline. Fiberglass de-waxing is necessary because visible and invisible release agents remain on the hull from the manufacturing process. Since this product contains strong solvents, it should not be used on polyester resin that is not fully cured since softening