Toughened Glass

• made in either plate , sheet or float glass . 
• The glass is heated and suddenly cooled by jets of cool air . 
• The cooled surface is put to compression while the interior is still in tension . 
• There may be some distortions but the glass becomes stronger , tougher and flexible than the original annealed glass . 
• Toughened glass is de-toughened by exposing to temp of about 300 celcius for long duration or too frequently and it is not fire-resisting  . 
• It is also called tempered glass .