Glass is an amorphous, brittle material created from a mixture of metallic silicates or borates, notable for its lack of a definite melting point and high compressive strength. The manufacturing process involves melting raw materials, forming and shaping, and finishing to produce various types of glass like soda-lime, potash-lime, and lead glass, each with specific properties and uses. Applications range from everyday items like bottles and windows to specialized glassware used in laboratories and for optical purposes.

2. GLASS
 Definition
 Preparation
 Composition
 VARIETY
 Uses

3. DEFINITION
Glass is an amorphous, hard, brittle, transparent or
translucent super cooled liquid of infinite viscosity,
having no definite melting point obtained by fusing a
mixture of a number of metallic silicates or borates of
Sodium, Potassium, Calcium, and Lead.
It possess no definite formula or crystalline structure:
 “An inorganic product of fusion which has cooled to a
rigid condition without crystallizing”
 Does not have a specific melting point
 Softens over a temperature range

4. PROPERTIES OF GLASS
 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

5. RAW MATERIALS USED IN MANUFACTURING GLASS
Raw Materials
 Sodium as Na2Co3 .
 Potassium as K2Co3 .
 Calcium as lime stone, and lime.
 Lead as litharge, red lead (flint glass).
 Silica arc quartz, white sand and ignited flint.
 Zinc is zinc oxide (Heat and shock proof glass).
 Borates are borax, Boric acid (Heat and shock proof
glass).
 Culets or pieces of broken glass to increase fusibility.

6. GLASS COMPONENTS
 Formers – Network Formation
SiO2, B2O3, P2O5, GeO2, V2O5, As2O3,
Sb2O5
 Fluxes – Softeners
Na2O, K2O, LiO, Al2O3, B2O3, Cs2O
 Stabilizers – Provide Chemical
Resistance
CaO, MgO, Al2O3, PbO, SrO, BaO,
ZnO, ZrO

7. MANUFACTURING STEPS
 Melting
 Forming and Shaping
 Annealing
 Finishing

8. MELTING PROCESS
1). Raw materials in proper proportions are mixed with culets.
2).It is finely powdered and intimate mixture called batch is fused
in furnace at high temperature of 1800°C this charge melts
and fuses into a viscous fluid.
CaCO3 + SiO2  CaSiO3 + CO2
Na2CO3 + SiO2  Na2SiO3 + CO2
3).After removal of CO2 decolorizes like MnO2 are added to
remove traces of ferrous compounds and Carbon.
Heating is continued till clear molten mass is free from
bubbles is obtained and it is then cooled to about 800°C.

9. FORMING, SHAPING, AND ANNEALING
 Forming and Shaping.
The viscous mass obtained from melting is poured into
moulds to get different types of articles of desired shape by
either blowing or pressing between the rollers.
 Annealing.
 Glass articles are then allowed to cool gradually at room
temperature by passing through different chambers with
descending temperatures. This reduces the internal Strain
in the glass.

10. FINISHING
Finishing is the last step in glass manufacturing.
It involves following steps.
 Cleaning.
 Grinding.
 Polishing.
 Cutting.
 Sand Blasting.

11. 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

12. POTASH LIME 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.

13. 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.
 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.

14. BOROSILICATE
 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.
 It is common hard glass
containing silica and boron
with small amount of
alumina and less alkaline
solids.

15. ALUMINO-SILICATE GLASS
 The typical approximate composition
of this type of glass SiO2(55%),
Al2O3(23%), MgO(090, B2O3(07%),
CaO(05%) and Na2O, K2O(01%).
 This type of glass possess
exceptionally high softening
temperature.
 Uses:
It is used for high pressure
mercury discharge tubes,
chemical combustion tube and
certain domestic equipments.

16. 99.5% VITREOSIL GLASS
 It contains pure silica heated to
its melting point. It is translucent,
the coefficient of thermal
expansion is very low hence it has
high resistance to thermal shock,
have high chemical resistance to
corrosive agents.
 If Vitreosil glass is heated above
its melting point, it becomes
transparent and is known as clear
silica glass.
 Uses:
They are used in construction of
chemical plants, laboratory
crucibles, induction furnace lining,
electrical insulators and heaters
and have high light transmission
properties.

17. SAFETY 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.

18. OPTICAL OR CROOK’S GLASS
 It contains Phosphorus, PbCO3, silicates and
Cerium oxide which has the property to absorb
harmful ultra-violet light. This glass is given
through homogeneity by heating it for a
prolonged period of time. These glasses have
low melting point and are relatively soft.
 Uses:
They are used for making optical lenses.

19. COLOURED GLASS
Addition of transition metal compounds to glass gives
color to the glass. They are outlined below.
Yellow: Ferric Salts Green: Ferrous and Purple: Magnese dioxide
Chromium salts salt
Red: Nickel and cuprous Lemon Yellow: Cadmium Fluorescent greenish
salts Cu2O sulphide yellow: Uranium oxide
Blue: Cobalt Salts, CuO Greenish Blue Color: Brown: Iron
Copper Sulphate
Opaque milky white: Ruby : Auric Chloride
Cryolite of Calcium

20. WIRED 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

21. 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

22. NEUTRAL GLASS
 These glasses are highly resistant to chemical attacks and they are
specialized soda lime glass where alkali has been replaced by alumina,
boron oxide and zinc oxide.
 Uses:
Making Syringes, Injection Ampoules and vials etc.

23. LAMINATED GLASS
 The sheets of glass fiber or glass wool are soaked in a solution of
thermosetting plastic like phenol formaldehyde resin and placed one
above the other and then cured under heat or pressure. It is strong as
steel. Non flammable and insulating. In bullet resistant glass vinyl
resins are added in alternate layers.
 Uses:
Shatter, shock and
Bullet proof Glass

24. 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.

25. 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….

27. IT IS CLEAR THAT GLASS PLAYS
A VITAL ROLE IN OUR
LIFE…GLASS COVERS A VERY
LONG JOURNEY BEFORE IT
COME TO US..AND IT’S REALLY
HARD TO MAKE GLASS. SO BETTER
WATCH BEFORE CRACKING ONE.