Fiberglass Supply Depot Wax Additive 4 oz Gelcoat & Polyester

Fiberglass Supply Depot Wax Additive 4 oz creates a tack-free surface when mixed into Gelcoat or polyester resin for a smooth sandable finish for easy polishing

Designed for marine and fiberglass projects, this surfacing agent can improve the final appearance of boat molds, repairs, and molded parts by delivering a tack-free surface that polishes to a professional sheen. By migrating to the surface during cure, the wax forms a barrier that helps seal out oxygen, supporting a consistent cure and a smooth, sandable finish.

Usage notes and typical dosing are provided to help you achieve reliable results in a variety of conditions. Typical mix ratio is approximately 4 oz per gallon of gelcoat, with adjustments for thinner or thicker formulations, and for weather or cure speed. The MEKP catalyst is still required; this additive does not replace hardener and should be counted in your resin formulation. Apply the wax only to the final gelcoat layer or final resin coat to avoid bonding issues with underlying layers. Do not use in laminating or build-up coats, as the wax barrier can prevent a strong chemical bond. After cure, the surface is ready for sanding, polishing, and cosmetic finishing on marine, fiberglass, or composite parts.

Features:

• Creates a tack-free surface: Wax additives mixed into gelcoat help eliminate the sticky surface caused by air exposure, allowing the gelcoat to cure fully and be sanded or polished once cured
• Used only in final/top coats: Add the wax additive only to the final gelcoat layer (or final polyester resin layer) — do not add to intermediate layers that need bonding.
• How it works: The wax (often paraffin or styrene-based) migrates to the surface during cure, forming a thin barrier that blocks oxygen and lets the resin cure hard all the way to the surface.
• Dosage matters: Typical ratios are around 1 oz per quart or ~4 oz per gallon of gelcoat — too much can cause defects like “fish eyes” or uneven finish.
• Catalyst still required: Wax additive doesn’t replace hardener — you still must add the correct amount of MEKP catalyst to gelcoat for polymerization to occur.
• Terminology: These products are often called wax additive, surfacing agent, or surface seal for gelcoat/polyester resin.