MODEL RELEASED. Catalytic hardening of fibreglass resin. Catalyst being added to a beaker of fibreglass resin. The resin (poured from the tin at left) is liquid, and needs to have this catalyst added to it to make it harden. The hardener contains free radicals that initiate the setting process, triggering a cascade of bond formation that turns the liquid resin into a hard, glassy solid. Fibreglass is a fibrous form of glass that is tougher than ordinary glass. The resin is Fastglas from the David's company. The hardener is benzoyl peroxide (BPO). See A500/684 for another example of a catalytic hardening process.