Best Gelcoat Additives for Spraying and Repairs

What Can I Add to Gelcoat to Help Spray It?

When spraying gelcoat, certain additives can improve flow, atomization, and surface finish. At Fiberglass Florida, we recommend the following products for best results:

• MEKP Catalyst – Required for all polyester and vinylester gelcoats. Mix at 1.5% to 2% by volume to initiate proper curing.
• Styrene Monomer – Can be added to thin gelcoat and improve spray flow. Limit usage to no more than 10% by volume to avoid reducing UV stability or surface hardness.
• Duratec 904-001 High Gloss Additive – A premium additive that can be mixed up to 1:1 with gelcoat to improve sprayability, eliminate porosity, increase gloss, and promote air cure. Excellent for tooling, repairs, and part refinishing.
• Patch Aid 970X900 Additive – Designed specifically for gelcoat repair work. Enhances spray flow, prevents orange peel, and reduces post-sanding. Also helps gelcoat cure tack-free in open-air applications.
• Wax Additive – Add at 2% to 4% only when the gelcoat will be exposed to air, such as in repairs or final coats. It forms a surface barrier that allows the gelcoat to cure fully and tack-free. Do not use wax additive when applying gelcoat between laminate layers or when secondary bonding is required.

Note: Always follow manufacturer mixing guidelines and test small batches before spraying large surfaces. Overuse of thinning agents or additives can compromise color, hardness, or UV resistance.

Need help choosing the right additive for your application? Contact Fiberglass Florida or visit our gelcoat section for all sprayable gelcoat systems and accessories.