Tempering is athermanl process by which the basic strength of glass is enhanced .During this process the annealed glass is heated to near softening point and then is rapidly cooled by directing Air jets over the surface of glass. This result in surface getting cooler faster than the core of the glass inducing stresses under compression on the surface and tension at the core. Ultimately the glass becomes stronger with higher resistance to thermal and impact load. The above process however does not change the visible and solar factors of the glass thus keeping the basic qualities
same while enhancing the strength. Fully tempered glass is almost 4 to 5 times stronger than normal annealed glass. Further, breakage of tempered glass will result in breaking of glass in small diamond like cluster with very low risk factor and hence are sometimes referred to as safety glasses also. However the risk factor is not as low as in case of laminated glasses.