Tempered Glass or Toughened Glass is made by processing normal annealed glass. The glass is subjected to heat till its softening point & then rapidly cooled in a controlled atmosphere.
A fully tempered glass is 4 to 5 times stronger than a normal annealed glass of similar thickness & size A fully tempered glass is considered as a safety glass as it will disintegrate into small & blunt pieces when broken, therefore reducing the probability & degree of injuries. Tempered glasses can also withstand high temperature differentials as compared to non tempered glass thereby reducing thermal breakage
Toughening process does not change the light transmission and solar prosperities of the glass. However tempered glass cannot be cut or altered. Therefore, it is made as per the requirement of the customer and all cutting, grinding, holes, cutouts, etc has to be done before the tempering process.
Glass cannot be cut or altered after tempering.
The raw material used in the manufacturing of tempered glass are not free from certain defects, like Nickel Sulfide inclusions, which put tempered glass at potential risk of spontaneous breakage.
Waviness & bending.
Tempered glass has some roller marks and more distortion than annealed glass.
Tempered glass as single glass should not be used for critical applications like overhead glazing where humans may walk.