ToughGlaze produce Heat Strengthened glass as part of its product range. The Heat strengthening process changes the surface compression of the glass usually to a level greater than 4000psi and less than 7000 psi. In turn the glass becomes 2 - 3 times stronger than normal annealed glass (it is not classed as a safety glass). Heat strengthened glass has three main criteria, Thermal Safety, Reduced Surface Distortion and when broken the glass cracks into large particles, whilst maintaining rigidity giving improved retention in the glazing system thus reducing the chances of falling glass.