Heat Strengthened Glass

Heat strengthened glass is similar to tempered glass except that the cooling is done at a much slower pace. Annealed glass is heated to approximately 650-700 � C, but the cooling process is slower than that for tempered glass. Heat strengthened glass is about twice as strong as annealed glass of the same size and thickness. Heat strengthened glass is a semi tempered glass which retains the normal properties of ordinary float glass. Heat Strengthened glass has been strengthened thermally by inducing a surface compression of 6000 to 9000 psi as compared to a range of 11000 to 20000 psi in case of fully tempered glass. Heat strengthening adds strength to the glass while limiting the change in its breakage characteristics. The cooling process places the surfaces of the glass in a state of high compression and the central core in a state of compensating tension.