Heat-treated Glass

This is glass that has been thermally processed to impart strength and/or safety features into the glass.  There are two types of Heat-treated glass:  Heat-strengthened and Fully Tempered (aka tempered).  Fully Tempered glass is approximately 4-5 times stronger than annealed (non-heat-treated) glass.  When it breaks it dices in to small, relatively harmless pieces that quality as a safety glass. Heat strengthened glass is about 2 times as strong as annealed glass.  When it breaks the pattern is similar to the large shards of annealed glass and therefore is NOT considered to be a safety glass.  

Both heat strengthened and fully tempered glass are processed on the same way on a horizontal furnace.  The glass is cut to size first an conveyed on rollers through the  furnace. ...