What is meant by ‘Toughened Glass’?
Ans.
Toughened glass or Tempered glass is a type of safety glass and has
increased strength. It will usually shatter in small pieces, rather small cubes, when broken. It is
used when strength and safety are important considerations. Since it shatters
in small and blunt pieces, it will not harm anyone. These are normally used for
panes of automobile vehicles, large glass shutters, large show wind panes, display cases etc., in order to prevent the the injuries due to likely
accidents. Toughened glass also has strength against impact four to six times
that of normal glass.
The
technique used to create toughened glass involves heating glass beyond 600 degrees centigrade. How far
beyond, determines the varying grades of "toughening". Once the glass is heated, the outside is rapidly and
artificially cooled, usually by jets of cool air. This method solidifies only
the outside, leaving the interior molten and fluid. That's what creates the
various layers within the glass.
It
should also be noted that after the glass is toughened operations like
drilling, cutting or grinding edges cannot be done. Hence, these operations are
needed to be carried out before toughening.
Toughened glass is physically and thermally stronger than regular glass. The greater contraction of the inner layer during manufacturing induces compressive stresses in the surface of the glass balanced by tensile stresses in the body of the glass.
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