Tempered glass is one form of “safety glass”. The original glass is treated thermally to increase its strength, making it a stronger and safer form of glass which is often required for many applications. Tempering involves heating the glass to a point just before melting temperature, and then quenching it rapidly. The stress caused by this rapid quench will result in a significant increase in strength. If broken, the glass will crumble into tiny blunt pieces, rather than jagged shards (as annealed glass would).