Gel Coat Catalyst Hardner (MEKP)

The Catalyst (MEKP) is a small bottle of methyl ethyl ketone peroxide (MEKP), a chemical hardener essential for curing polyester and vinyl ester resins, including gel coats. When added to these resins, MEKP initiates a chemical reaction that transforms the liquid resin into a solid state, making it a critical component in fiberglass work, boat repairs, and mold making.  MEKP is a hazardous material. It is flammable, corrosive, and can cause severe burns or eye damage upon contact. Always wear appropriate personal protective equipment (PPE) such as gloves, goggles, and work in a well-ventilated area. Due to its hazardous nature, MEKP is often restricted to ground shipping only. If you're new to working with fiberglass or resins, it's crucial to follow the resin manufacturer’s instructions for the correct MEKP ratio and curing times. Too much catalyst can cause the resin to cure too quickly, generating excessive heat, while too little may result in incomplete curing. Prepare Your Work Area Make sure you're in a well-ventilated space. Wear protective gloves, goggles, and a respirator—MEKP is hazardous. Make sure your tools (spray gun, mixing container) are clean and ready. Measure and Mix Pour the gel coat into a clean mixing cup. Add 1–2% MEKP by volume (e.g., about 10–20 drops per ounce of gel coat, or ~10 cc per quart, depending on temperature). Use 1% in warm weather (fast cure). Use 2% in cooler temperatures (slower cure). Stir thoroughly but gently for at least 60 seconds to ensure an even mix. Avoid whipping air into the mixture, which causes bubbles. Application Apply the catalyzed gel coat immediately—you have a working time of about 15–20 minutes, depending on temperature. Use a cup gun or spray gun for even application. You can also brush it if doing small repairs. Curing Allow the gel coat to cure fully. It should firm up in 1–2 hours. Don’t touch or rework the surface until it's fully hardened. Cleanup Clean all tools with acetone before the gel coat hardens. ❌ Do NOT: Do not spray MEKP separately or after the gel coat—it must be mixed in beforehand. Do not over-catalyze (more than 2.5%)—it can cause cracking or excessive heat.