What is a hardener or activator?

• A. A chemical that helps paint cure
• B. A solvent for thinning
• C. An additive that increases drying time
• D. A deodorizer for solvents

Answer: (A)

Two-part coatings rely on a hardener (activator) to start the curing reaction. When you mix the paint with the hardener, reactive groups in the hardener bond with the resin, creating cross-links that turn the liquid film into a solid, hard, durable coating. This is what gives the finish its adhesion, hardness, and chemical resistance.

It's not a thinning solvent you add to reduce viscosity, and it doesn't simply deodorize solvents. The hardener is a reactive component that drives the cure, often setting a specific pot life and requiring the correct mix ratio and conditions to achieve proper hardness. If the ratio or conditions aren’t right, the film may cure poorly or remain soft.