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.
