Pilkington Pyrostop^® is a clear, multi-layered fire-resistant glass made of low-iron float glass (Pilkington Optiwhite™), laminated with special transparent intumescent interlayers.

When exposed to fire, the pane facing the flames fractures but remains in place, and the interlayer immediately foams up to form a thick, resilient and tough insulating shield that absorbs the energy of the blaze. This takes place at relatively modest temperatures around 120°C, such that protection is provided right from the early stages of a fire.