Toughened (tempered or security)

Is produced by heating annealed glass to approximately 650 c at, which point it begins to soften. The surfaces of this heated glass are then cooled rapidly. The technique creates a state of high compression in the outer surfaces of the glass. As a result, although most other characteristics remain unchanged, the bending

Strength is usually increased by a factor of four or five times that of annealed glass. When broken, the toughened glass fractures into small pieces. As these particles do not have the sharp edges and dagger points of broken annealed glass toughened glass is regarded as safety glass and safety glazing material. Toughened glass must be cut to size and have any other processing, such as edge polishing and hole drilling, completed before being subjected to toughening, because attempts to ‘work” the glass after toughening will cause it to shatter.

The toughening process imposes limits on the maximum glass sizes wired glasses couldn’t be toughened.

·       Heat strengthened glass.

Is produced by a process similar to that used for toughened glass, but the cooling process is slower. The strength developed is about half that of toughened glass and distortion is generally less. That product has many uses, but it does not meet the criteria for safety glazing because its breakage pattern resembles that of an annealed glass.

Tempering & heat strength process. 

·        Minimum tempering size (200 x300)

·        Maximum tempering size (2440 x 5000) please note that the maximum size is not available in all glass types as maximum stock sheet sizes of glass do Tend to vary. Max. Manufacturing sizes are not necessary safe glaze sizes

·        Minimum glass thickness for tempering 4 mm.

·        Maximum glass thickness for tempering 19 mm.  

·        Wired glass cannot be tempered. Also the glass supplier should temper the soft coating glass. i.e.(ss, Ts……..etc coatings).

·        Any glass edges should be arise before tempering.

·        Dimension tolerances for rectangles & squares (+/-) 2mm.on dimension; 5mm on square ness.

·        Bow tolerances affected by various factors such as thickness, size, length to width ratio according to that the normal bow allowed

     1mm.per meter up to 1meter dimension and 2mm. Per meter for over 1meter dimension.