Toughened glass is also know as Tempered glass.
Toughened or tempered glass is a type of safety glass
processed by controlled thermal or chemical treatments to
increase its strength compared with normal glass.
Tempering puts the outer surfaces into compression and
the inner surfaces into tension. Such stresses cause the glass, when
broken, to crumble into small granular chunks instead of
splintering into jagged shards. The granular chunks are less likely
to cause injury.
The first patent on tempered glass was held by
chemist Rudolph A. Seiden, born in 1900 in Austria.
Though the underlying mechanism was not known at the
time, the effects of "tempering" glass have been known for
Its popularity has increased in recent decades because of
its use in the automobile and construction industries, as well as in
microwaveable glassware. Among the most common current uses
are for side and rear windows and windshields in automobiles,
display cases, patio doors, and shower doors.
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. For glass to be
considered toughened, this compressive stress on the surface of the glass
should be a minimum of 69 MPa. For it to be considered safety glass, the
surface compressive stress should exceed 100 MPa. The greater the
surface stress, the smaller the glass particles will be when broken
Any cutting or grinding must be done prior to tempering.
Cutting, grinding, sharp impacts and sometimes even scratches after
tempering will cause the glass to fracture
The strain pattern resulting from tempering can be observed
with polarized light or by using a pair of polarizing sun glasses.
STEPS INVOLVED IN MANUFACTURING
OF TOUGHENED GLASS
Steps involved in making tempered glass are as
1. Cut the glass into the desired shape first.
2. Inspect the glass for imperfections
3. Sand the cut edges smooth
4. Wash the glass
5. Heat the glass in a tempering oven
6. Quench the glass to cool it
Glass type Toughened glass
Thickness (mm) 2.8 3 4 5 6 8 10 12 15 19 22 25
Transparent, Bodily colored, Colorfully
glazed, Film plated and Toughened glass
Toughened insulating glass, Toughened
laminated glass and Toughened insulating
Max size possible
5100 x 3200
Min. size possible
300 x 300
SPECIFICATIONS & SIZES OF TOUGHENED
Through the quenching process , the inside of
toughened glass possesses the compressive stress , it
will with stand the impact force to certain extent, even
though it encountered greater load of impact and broke,
its fragments seemed to lot of tiny particles with obtuse
angle that hardly would do any harm to human body.
While with the fragments of ordinary glass, they are
similar to large size broken sharp pieces easily causing
serious injuries to the people.
Toughened glass is used when strength, thermal resistance,
and safety are important considerations. The most commonly
encountered tempered glass is that used for side and rear windows
It is used for its characteristic of shattering into small cubes
rather than large shards and is sometimes referred to as safety glass
in this context
Toughened glass is also used in buildings for unframed
assemblies (such as frameless doors), structurally loaded
applications, and any other application that would become
dangerous in the event of human impact.
The term "toughened glass" is generally used to describe
fully tempered glass but is sometimes used to describe heat-
strengthened glass as both types undergo a thermal "toughening"
There are two main types of heat-treated glass: heat-
strengthened and fully tempered. Heat-strengthened glass is twice as
strong as annealed glass while fully tempered glass has typically
four to six times the strength of annealed glass and withstands
heating in microwave ovens. The difference is the residual stress in
the edge and glass surface
It is important to note that the tempering process does not
change the stiffness of the glass. Annealed glass undergoes a similar
deflection compared to tempered glass under the same load, 11
Toughened glass must be cut to size or pressed to shape
before toughening and cannot be re-worked once toughened.
Polishing the edges or drilling holes in the glass is
carried out before the toughening process starts.
Because of the balanced stresses in the glass, damage to
the glass will eventually result in the glass shattering into
For any mistakes and suggestion’s feel free to text here
Steps involved in the manufacturing process of TOUGHENED
GLASS can be seen in my next upload.