ENTROPY BRT SYSTEM is an optically brightened, clear laminating system, designed specifically for ultra-white cosmetic applications such as surfboard laminations over EPS (polystyrene) or PU (polyurethane) foam. Based on Entropy Resins’ classic CLR – CLEAR Laminating Epoxy Resin,. BRT OPTICALLY BRIGHTENED Epoxy Resin can be paired with all of 'CL' Clear Hardeners.