Matte Clear Hardener Part B - QuartPOR 15 Part B Matte Clear Coat Hardener Activator is a urethane catalyst that activates the curing process for POR 15 two part coatings. POR 15 Part B Matte Clear Coat Hardener Activator is a moisture reactive compound and must be stored in an air tight, full to the brim container or shelf life will be diminished considerably. Mixing Directions: See accompanying container Matte Clear Coat (Part A) for mixing directions.