Catalysts are mixed into resins, gelcoats, topcoats and bonding paste to initiate the curing reaction to turn the liquid or paste into a solid, durable material. MEKP (standard bottled catalyst) is used for resins, gels and topcoats. BPO paste is used for bonding paste. The addition for both is 2% at room temperature. More or less may be required depending on the working temperature (slightly less for warmer conditions and more for colder climates). Generally, never less than 1% and never more than 4%. This material is highly flammable and corrosive, great care should be taken when handling this product.