2. ENGINEER LATIF HYDER WADHOENGINEER LATIF HYDER WADHO
Mehran University of Engg: & Technology KhairpurMehran University of Engg: & Technology Khairpur
Civil Engineering MaterialsCivil Engineering Materials
11stst
Term 1Term 1stst
Year B.E.CivilYear B.E.Civil

3. GLASS
AND
ITS
MANUFACTURIN
G

4. GLASSGLASS
Glass is obtained by fusion of silica, chalk
(lime) and potash or soda at over
10000
C.In order to modify its properties of
hardness, brittleness and colour ,other
ingredients like iron oxide, lead
oxide,borax,etc are added in varying
proportions.
Functions of various important constituents
of glass are given below.

5. (1) Silica (SiO2):
It is the major constituent of all types of
glass. As it fuses at very high
temperatures some alkaline admixtures
like sodium carbonate or potassium
carbonate is added to it so as to make it
fuse at lower temperature. The
admixtures added to lower the fusion
temperature also make the liquid silica
viscous and better workable.

6. (2) Potash:
It renders glass infusible and
gives fire resisting properties to it.
(3) Soda:
It accelerates fusion of glass; as
such excess of it is harmful.

7. (4) Lime (CaO):
It gives durability and toughness
(hardness) to glass.
(5) Lead oxide:
It gives colour to glass.
(6) Cullet:
It is broken glass, which is used as a
raw material to reduce to its cost.

8. All the constituents of glass discussed above are
separately ground, sieved and mixed in definite
proportions. The mix is then fused in a tank furnace
or in a pot furnace.
Tank Furnace:
It is used for large scale productions.
Pot Furnace:
It is used for smaller production but of superior
quality.
In the furnace all the ingredients are turned into
molten state and then desired shape of glass is
obtained by Blowing, Flat drawing, Rolling,
Compression moulding and Spinning (pulling), etc.

9. CLASSIFICATION OF GLASS:
BASED UPON ITS
COMPOSITION:
Glass is generally classified in to three
categories.
(1) Soda lime/soda ash/soft
Glass:
It is obtained from the fusion of a
mixture of silica, lime, soda and
alumina. Powdered glass too may be
added.

10. (2) Lead Glass:
It is obtained from the fusion of a
mixture of silica, lead and potash.
Powdered glass is added.
It has shining appearance and takes
good polish. It is not affected by
temperature.
It is used for cut glass work, electric
bulbs.

11. (3) Boro-silicate Glass:
It is obtained from the fusion of a
mixture of silica, borax, lime, etc.
Powdered glass too may be added.
It can with stand high temperature.
It is used for manufacturing of
laboratory equipments and cooking
utensils.

12. SPECIAL COMMERCIAL
FORMS OF GLASS:
For various engineering and
industrial requirements special
varieties of glass with the
desired specifications are made.
These include the following:

13. (1) Sheet Glass:
Sheet glass is made by blowing.
It is available within 2 to 6 mm
thicknesses.
It is mainly used as door and
window panels and for all kinds
of glazing works.

14. (2) Plate Glass:
Molten glass is rolled into plate
glass with thicknesses varying from
6 to 25mm. It is also suitable for
glazing works, as table tops,
windows, train carriages, buses,
cars, the windscreens and superior
quality mirrors.

15. (3) Coloured Glass:
It is prepared by mixing different
pigments at the fusion stage. It
diffuses the light passing through
it. It is also called as stained
glass.
It is used in decorative works.

16. (4) Wired Glass:
This is the plate and sheet glass in
which steel wires or mesh is
embedded during the rolling process.
The steel wire acts as reinforcement.
It is also called as reinforced glass.
It is used for sky-lights, high class
roofing works and fire proof doors
and windows.

17. (5) Structural Glass:
This type of glass is used in constructional
works and can be embedded anywhere within
the walls and ceilings. It is made in the form of
hollow square blocks, tiles, bricks and lenses.
It is light in weight. It can be easily cut and
drilled.
It is used for transparent face work, partition
walls, roofing and flooring works where ever
light is desired to pass through. It is also used
for heat and sound insulation works.

18. (6) Laminated Glass:
This is also safety glass; it
consists of sheets of glass glued
together with a celluloid layer
between them.
It is used for the wind screens
and rear glass in the automobiles
etc.

19. (7) Bullet-Proof Glass:
This is bullet-resistant glass. It consists of a
number of glass layers alternating with vinyl-
resin plastic layers, pressed together. The
inner glass plates are thick and cooling
process is carried out under specially
controlled manner. It is made in variable
thicknesses, varying from 15mm to 80mm.
This glass is used when extra safety
measures are required. It is used in aircrafts,
bullet proof automobiles, cabins, offices and
enclosures.

20. (8) Fibre Glass:
This is also described as glass
wool; it is in the form of glass
fibres which are soft and flexible.
It is highly resistant to wear and
tear.
It is mainly used for all kinds of
thermal and sound insulation
works.

21. (9) Foam Glass:
It is porous or cellular variety of glass, light
in weight but rigid in form. It is water proof.
Also it is good heat insulator. It can be
sawn or cut into any shape or size like
wood. It is prepared by heating the mixture
of a finely ground glass and carbon.
It is used for all kinds of thermal and sound
insulation works. It is also used for
refrigeration and air conditioning works.

22. (10) Flint Glass:
It is the glass containing lead which
makes it highly shining and capable of
high polish. It is costly glass. It is also
known as shielding glass as it stops
different kinds of radiations. It is widely
used for high-class glass ware like cut
glass, table glass, as optical glass for
lenses, prisms and slabs, electric bulbs,
electric tubes, radio valves, etc.

23. (11) Soluble Glass:
It is that type of glass which is
soluble in water. It may be kept in the
form of small chips or pieces or in
liquid glass. It is prepared by melting
a mixture of silica and sodium
sulphate or potassium carbonate.
The soluble glass is used for mixing
with cement to make it resistant to
the acids.

24. PROPERTIES (OR) CHARACTERISTICS OF
GLASS:
(1) It has highly shining appearance and takes good
polish.
(2) It is not affected by temperature except in some
exceptional cases.
(3) It is fire retardant.
(4) It provides heat insulation.
(5) It also ensures transmission of light.
(6) It is available in various varieties.
(7) It transmits light but also provide privacy by
obstructing vision.
(8) Glass blocks provide heat and sound proof
properties.

25. USES OF GLASS:
(1) Glass is extensively used in building construction
since long time for glazing doors and windows.
(2) It is also used for decoration.
(3) It is also used for sound insulation purposes.
(4) It is used for cut glass work, electric bulbs (lead
glass).
(5) It is used for manufacturing of laboratory
equipments and cooking utensils (Boro-silicate
glass).
(6) It is used for partition walls.
(7) It is used for cabinets, show cases, shop fronts.
(8) It is also used as fire retarder.

26. ANNOUNCEMENT
SESSIONAL TEST
Date : 13 April, 2012
Day : Friday
Time : During CEM Class