Heat-Strengthened Glass
Glass that has been heat-treated to approximately twice the strength of annealed glass, but less than tempered glass. It breaks into larger pieces than tempered glass.
Heat-strengthened glass occupies a middle ground between annealed and tempered glass. It is approximately twice as strong as annealed glass but does not qualify as safety glass because it breaks into larger fragments. It is commonly used in spandrel applications and areas where resistance to thermal stress is needed but safety glass is not required.