LECTURE- GLASS

AS A BUILDING MATERIAL

-AR. SHIVANI VARMA

 GLASS
WHAT IS GLASS?

SUPERCOOLED LIQUID
LIQUID WHICH IS COOLED TO A STAGE
WHERE ITS VISCOSITY IS SO GREAT THAT
THE MOLECULES DO NOT MOVE FREELY
ENOUGH TO FORM CRYSTALS
 PROPERTIES OF GLASS
Glass is:
• Amorphous
• Brittle
• Transparent / Translucent
• Good electrical insulator
• Unaffected by air, water, acid or chemical reagents except HF
• No definite crystal structure means glass has high Compressive
strength
• Can absorb, transmit and reflect light
 WHAT IS GLASS MADE OF?

Sand – 70%
Soda Ash – 15%
Limestone – 10%

CSP TRG AIDS - AUG 2008 4

SILICA SAND
 SILICA SAND

Three of most common rock forming minerals on earth. Chemically

named: quartz sand / rock crystal
Properties: Extremely heat durable
Chemical stack resistance
 SODA ASH

Anhydrous sodium carbonate

Texture: soft
Color: grayish & white
Appearance: lump / powder in nature
 LIME
Includes hydrated lime Ca (OH)2 & quicklime CaO
Only quicklime can use to make glass
 COMPOSITION OF GLASS

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.
 COMPOSITION OF GLASS
2. Potash: It gives fire resisting properties to it.
3. Soda Ash: It accelerates fusion of glass; as such excess of it is harmful.
4. Lime (CaO): It gives durability and toughness (hardness) to glass.
5. Lead oxide: It gives color to glass.
6.Cullet: It is broken glass, which is used as a raw material to reduce to its cost.
 COMPOSITION OF GLASS
• The glass is not a single compound. It is therefore very difficult to give any
particular chemical formula for it. It may be generally be expressed as
follows:
a X2O, bYO, 6 SiO2

where a and b are number of molecules,

X= an atom of an alkali metal such as Na, K, etc.
y= an atom of bivalent metal such as Ca, Pb, etc.

With this expression, chemical formula of three groups of glass are as follows:
Soda-lime glass : Na2O, CaO, 6 SiO2
Potash-lime glass: K2O, CaO, 6 SiO2
Potash-lead glass: Na2O, PbO, 6 SiO2
 MANUFACTURING OF GLASS

• COLLECTION OF RAW MATERIALS

• PREPARATION OF BATCH

• MELTING IN FURNACE

• FABRICATION

• ANNEALING
MANUFACTURING OF GLASS
 FINISHING
Finishing is the last step in glass manufacturing. It involves following steps.

❑ Cleaning
❑ Grinding
❑ Bending
❑ Polishing
❑ Cutting
❑ Opaque making
❑ Silvering
❑ Sand Blasting

❑ Colored glass
TYPES OF GLASS
 COMMERCIAL GLASS OR
SODA LIME OR SOFT GLASS
• About 90% of all glass is soda-lime glass made with silica (sand),
Calcium carbonate and soda ash.
• The approximate composition is Na2CO3.CaO.6SiO2.
• They are low cost, resistant to water but not to acids.
• They can melt easily and hence can be hot worked.

• Uses:
Window glass, Electric bulbs, Plate glass, Bottles, Jars, cheaper
table wares, test tubes, reagent bottles etc
 POTASH LIME OR
BOHEMIAN GLASS OR HARD GLASS
• Potash lime glass is made with silica (sand), Calcium
carbonate and potassium carbonate.
• The approximate composition is K2CO3.CaO.6SiO2.
• They posses high melting point, fuse with difficulty and are
less acted upon by acids, alkaline and other solvents than
ordinary glass.

• Uses:
These glasses are costlier than soda lime glass and are used
for chemical apparatus, combustion tubes and glassware
which are used for heating operations.
 LEAD GLASS OR FLINT GLASS
• It is made up of lead oxide fluxed with silica and K2CO3 is used instead of sodium
oxide.
• Its approximate composition is K2Co3.PbO.SiO2.
• To get dense optical glasses about 80% lead oxide is used.
• Lead glasses has a lower softening temperature than soda glass and higher refractive
index and good electrical properties.
• It is bright lustrous and possess high specific gravity.

• Uses:
High quality table wares, optical lenses, neon sign tubing, cathode ray tubes, electrical
insulators, crystal art objects or cut glass, Windows and Shields for protection against
X-rays and Gamma rays in medical and atomic energy fields etc.
 BOROSILICATE / PYREX / JENA
• It is common hard glass containing silica and boron with
GLASS
small amount of alumina and less alkaline solids.
• It contains SiO2(80.5%), B2O3(13%), Al2O3(03%), K2O(3%)
and Na2O(0.5%).
• These glass have low thermal coefficient of expansion, and
high chemical resistance i.e..shock proof.

• Uses:
Industrially used for pipeline of corrosive liquids, gauge
glasses, superior laboratory apparatus, kitchen wares, chemical
plants, television tubes, electrical insulators etc.
 COMMON GLASS
• It is formed by mixing sodium silicate,calcium silicate and
OR BOTTLE GLASS
iron silicate
• These glass fuses with difficulty.
• It is brown, green and yellow in colour.
• It is easily attacked by chemicals
• Uses:
It is mainly used in manufacturing of bottles
SPECIAL TYPES OF GLASS
 SAFETY GLASS
Safety glass is glass with additional safety features that make it less likely to break, or less likely to
pose a threat when broken.

Common designs include

• toughened glass (also known as tempered glass),

• laminated glass,

• wire mesh glass (also known as wired glass) and

• engraved glass.
 TOUGHENED GLASS
Toughened glass is processed by controlled thermal or chemical treatments to increase its strength
compared with normal glass.
• Tempering, by design, creates balanced internal stresses which causes the glass sheet,
when broken, to crumble into small granular chunks of similar size and shape instead of
splintering into random, jagged shards. The granular chunks are less likely to cause injury.

• It is made by dipping articles still hot in an oil bath, so that

chilling takes place. This results in outer layer of articles shrink
and acquire a state of compression while inner layer are in
state of tension. Such glass is more elastic to mechanical and
thermal shock. It breaks into a fine powder.

• Uses:
For making window shields of fast moving vehicles, windows
of furnace and automatic opening doors.
 LAMINATED GLASS
• It is made by fusing two to three flat sheets of glass and in
between them alternate thin layer of vinyl plastic is introduced.
It is heated where both the layers merge together and glass is
toughened.

• Uses:
• It is used as wind shield in automobiles and airplanes.
On breaking it pieces does not fly apart because of the presence
of the plastic layer in between the glass layers.
 BULLET PROOF GLASS
• Bullet proof glass or bullet resistant glass refers to any type of
glass that is built to stand up against being penetrated by bullets.
• It is usually constructed using a strong but transparent material such as
polycarbonate thermoplastic or by using layers of laminated glass.
• The plastic provides little in the way of bullet-resistance. The glass,
which is much harder than plastic, flattens the bullet and thereby
prevents penetration. This type of bullet proof glass is usually 70–75
mm (2.8–3.0 in) thick.
• Bullet proof glass constructed of laminated glass layers is built
from glass sheets bonded together with polyvinyl butyral,
polyurethane or ethylene-vinyl acetate. This type of bullet proof glass
has been in regular use on combat vehicles since World War II; it is
typically about 100–120 mm (3.9–4.7 in) thick and is usually extremely
heavy.
 BODY-TINTED GLASS
• Body-tinted glass is normal float glass into which melt colorants are
added for tinting and solar-radiation absorption properties.
• It saves energy and reduces heat penetration into buildings and
gives a striking visual effect.
• Tinted glass refers to any glass that has been treated with a material
such as a film or coating, which reduces its ability to transmit light.
• Glare reduction is another important property of tinted glass.
• The production process of body-tinted glass is similar to that of float
glass. The only variation is in the colorants mixed at the beginning
with the standard raw materials. Body-tinted glass is produced when
colorants and iron are introduced during the glass manufacturing
process. Different additives may produce differently colored glasses.
Bronze, dark grey and green are the commonly used tints.
 COLOURED GLASS
Addition of transition metal compounds to glass gives color to the glass. They are outlined below.
Yellow: Ferric Salts Green: Ferrous and Chromium salts Purple: Magnese dioxide salt

Red: Nickel and cuprous salts Cu2O Lemon Yellow: Cadmium sulphide Fluorescent greenish yellow: Uranium
oxide

Blue: Cobalt Salts, CuO Greenish Blue Color: Brown: Iron

Copper Sulphate

Opaque milky white: Cryolite of Calcium Ruby : Auric Chloride

phosphate
 PHOTOVOLTAIC GLASS
• Photovoltaic glass is a special glass with integrated solar
cells that convert solar energy into electricity.
• The solar cells are embedded between two glass panes
and a special resin is filled between the panes, securely
wrapping the solar cells on all sides. Each individual cell
has two electrical connections, which are linked to other
cells in the module, to form a system which generates a
direct electrical current.
• Need for Photovoltaic Glass
Apart from providing privacy and protection from noise
and rain, other features such as thermal insulation and
shading are becoming increasingly desirable. All of these
functionalities can be obtained simply by installing
photovoltaic glass to the shell of a building.
 SELF-CLEANING GLASS
• Self-cleaning glass is a specific type of glass with a surface which
keeps itself free of dirt and grime through photocatalytic
decomposition.
• A nanometer-scale coating of titanium dioxide on the outer surface
of the glass introduces two mechanisms which give it the self-
cleaning property.
• Self cleaning glass cleans itself in two stages.
• The first stage is called photo-catalysis which is the action of
light on the surface of the glass to basically chomp away or
eat the dirt on the surface.
• The next is a process known as hydrophilicity. This basically
ensures that any water that falls on the surface forms sheets
and washes away dirt uniformly. The glass spreads the water
evenly over its surface, without forming droplets.
 SMART GLASS
• Smart Glass or Switchable Glass is a
product of cutting-edge technology that
allows users to block either all light or just
some by simply turning a knob or pressing
a button.
• Smart glass technologies include
• electrochromic devices,
• suspended particle devices and
• liquid crystal devices
• Suspended Particle Devices are constructed with two panes of
glass separated by a conductive film with suspended, light
absorbing, microscopic particles. These microscopic particles
within the Suspended Particle Devices (SPD) absorb light, thus
preventing it from passing through the film. When the electrical
current is added to the film, the particles align themselves to allow
light through the glass.
• Electrochromic Glasses work in the opposite manner. When a
current is supplied, they darken and when electricity is withheld
they become clear. Another unique aspect of these is that they
aren’t so black and white. Instead they are able to create varying
levels of light penetration, allowing total management of the
sun’s power.
 WIRED GLASS
• Wired or Wire mesh glass has a grid or wire mesh of thin metal embedded within the glass.
• Wired glass does not fall apart into splinters when it breaks and is fire resistant. It is made by fusing wire in
between the two glass layers.

Uses:
For making fire resistant doors, roofs, skylights and windows
 PHOTO-CHROMIC GLASS
• The three dimensional silicate network contains large no. of
microscopic particles of silver halide which on exposure to
light produce color.

• Uses:
In making tinted car glasses and goggles.
 FIBER GLASS
• It is transformed into a fine thread of filament and has got a high tensile strength.

Uses:
Found extensive use for the manufacture of fabric, reinforcing plastics and production of thermal
insulation materials etc
 PHOTOSENSITIVE GLASS
• These are glasses by which a colored picture may be
developed by exposing the glass to black and white
negative in ultra violet light.
• The appropriate proportions of potash-alumina
glass, mixed with LiSO3, cerium and Silver salts have
also been used as photosensitive glass.

• Uses:
Photographic development
 GLASS WOOL
• Glass wool consists of tiny fibers formed by action of
steam jets on dripping molten glass down from very fine
hole.

• Uses:
Heat Insulation, for filtration of Corrosive chemicals,
sound insulation etc
 INSULATING GLASS
• Two or more plates of glass are filled with dehydrated air and the edges are sealed air-tightly.

• Uses:
Provides thermal insulating and so houses remain cool in summer and warm in winter.
 FRACTURE / FAILURE OF GLASS
• Glass does not have crystal lattice structure hence it breaks. Fracture is caused by small imperfections,
flaws and irregularity on the surface of the glass. Flaws are very fine cracks cause concentration of stress
and the crack proceeds quickly causing a fracture.