Glass is an amorphous solid made through the melting and cooling of raw materials such as silica sand, soda ash, limestone, and recycled glass. There are many types of glass with different compositions and properties. Glass is manufactured through mixing raw materials, melting in furnaces, fabrication into desired shapes, and annealing to relieve internal stresses. Common glass products include float glass, fiberglass, safety glass, and specialty glasses used for optical, electrical, and scientific applications.

1. GLASS

2. UNIT V - GLASS
Composition of glass
Manufacture, Treatment, Properties, Uses of glass.
Types of glass - Float glass, Cast glass, Glass blocks, Foamed glass.
Decorative glass, Solar control, Toughened glass, Wired glass, Laminated
glass, Fire-resistant glass, Glass blocks, Structural glass
Properties and Application in building industry, Glazing and Energy
Conservation Measures

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.
I
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
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

5. Raw materials used in manufacturing glass
Raw Materials
• Sodium as Na2Co3 (used in soft glass).
• Potassium as K2Co3 (used in Hard Glass).
• Calcium as lime stone, chalk 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).
• Cullets or pieces of broken glass to increase fusibility.

7. Manufacturing steps
FIVE STAGES OF MANUFACTURE
1. Collection of Raw materials
2. Preparation of the Batch
3. Melting in Furnace
4. Fabrication
5. Annealing

9. Cullet –
1. Indicates waste glass or pieces of broken glass, They increases the
fusibility of glass
2. Prevent loss of alkali by vitalization during the reaction in forming new
glass
3. They also reduce the cost.

12. • The raw materials , cullet and de-colouriser are finely
powdered in grinding machines.
• They are accurately weighed in correct proportions before
they are mixed together.
• The uniform mixture is called Batch or Frit
Preparation of Batch

13. Melting process
 Raw materials in proper proportions are mixed with
cullets. 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.
POT FURNACE
TANK FURNACE

14. POT FURNACE TANK FURNACE

15. Fabrication of Glass
BLOWING- 12mm dia and 1.8m long blow-pipe is used. One end is
dipped in to molten glass and 50N of wt. of glass is taken out.
CASTING – Pouring into moulds-allowed to cool slowly
DRAWING – Iron bar dipped in molten glass sideways and sheets of glass
are drawn to spread in the form of thin sheet.
PRESSING- molten glass is pressed into moulds- mechanically or
manually
ROLLING- either passed between heavy iron rollers and flat glass is
obtained or poured on a flat ironcasting table and turned flat with heavy
iron rollers.
SPINNING – the molten glass is spun at high speed to obtain fine glass
fibres.It does not allow fade, decay and shrink

17. 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. Sudden drops
in temp is highly not recommendable.
1. Flue Treatment – large scale production.
2. Oven Treatment – small scale production.

18. Treatment of Glass
1. Bending – to rods, sheets or tubes
2. Cutting – cut using diamond/rough glass/steel
wheels
3. Opaque Making- grinding the surface with emery
or chemically treated (hydrofluoric acid)
4. Silvering- a thin coat of tin is applied to the
surface. Silver is deposited on this layer of tin. A
suitable paint is applied on top to give protection
against the atmospheric effects.

21. Varieties of glass
Soda lime or
soft glass
Potash lime or
hard glass
Lead glass or
flint glass
Borosilicate or
Pyrex glass
Alumino-
Silicate glass
Silica glass Soluble glass Safety glass
Optical or
Crook’s glass
Poly-crystalline
glass
Toughened
glass
Colored glass
Wired Glass Glass Wool Fiber glass Photosensitive
glass
Photo-chromic
glass
Neutral glass Laminated glass Insulating glass
Float glass, Cast glass, Glass blocks, Foamed glass. Decorative glass, Solar control,
Toughened glass, Wired glass, Laminated glass, Fire-resistant glass, Glass blocks, Structural
glass

22. Soda lime or soft glass
• About 90% of all glass is soda-lime glass made with silica
(sand), Calcium carbonate and soda ash.
• 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

23. Borosilicate / pyrex glass
• It is common hard glass containing
silica and boron.
• 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.

24. Lead glass or flint glass
• It is made up of lead oxide fluxed with silica
and K2CO3
• To get dense optical glasses about 80% lead
oxide is used.
• 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.

25. 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:
Copper Sulphate
Brown: Iron
Opaque milky white: Cryolite
of Calcium phosphate
Ruby : Auric Chloride

26. Safety glass
• Tempered Glass: The side and rear windows in most
consumer automobiles are customarily made of tempered glass
due to its high impact resistance and safe shattering qualities-
commercial building doors, bathtub and shower enclosures,
sliding doors
• Laminated Glass: Laminated glass provides improved
safety features .It can also be used for added security in windows
or balconies, aircraft windshields, and tank viewing windows.
• Armed Glass: Armed glass is most commonly used in the
roofing of industrial building or other outdoor structures. This type
of glass can provide additional light from above, but its metal grill
lowers overall visibility.

28. • Tempered glass is a glass that has been subjected to an
additional heat treatment after annealing in order to increase its
mechanical strength •
• The tempering process lies on the controlled creation of
permanent stresses in the glass
• Tempered glass can be as much as 4 to 5 times stronger than
annealed glass (without tempering) • When fracturing, tempered
glass breaks into small fragments. It is often referred to as “safety
glass
Tempered glass

29. Toughened glass
• 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.

30. 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

31. 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

32. Fibre 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

33. 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

35. Float Glass – The molten glass coming out of furnace is allowed
to float on the molten tin. This is annealed to remove all the stresses.
It is superior to ordinary glass in many ways
1. Environmental friendly
2. Aesthetically appealing
3. Available in larger sizes
4. Cost-effective compared to bricks, paints etc
5. Suitable for solar applications due to high light transmission
6. Tougher and more scratch resistant
7. Mirrors that give true mirrors
8. For ideal window
9. Optical clarity, superior saftey
10. No refraction defect due to uniform thickness and superior
optical clarity( eye lenses)

36. Foam Glass :
They are in the form of rectangular blocks. The finely ground
glass and carbon are thoroughly mixed and melted. At the
time of melting the mixture expands and assumes the form of a black
foam.
This floats in water and it can be cut like wood. It is fore proof, rigid
and excellent heat insulator. It is a substitute for cork.
Glass Blocks

37. 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.

38. 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.

39. Alumino-silicate glass
• This type of glass possess
exceptionally high softening
temperature.
• Uses:
It is used for high pressure
mercury discharge tubes,
chemical combustion tubes
and certain domestic
equipments.

40. silica glass / vitreosil
• 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.

41. Optical or crook’s glass
• It 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.

42. 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

43. 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.

44. 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.

45. Mitigate climate change
In many of its application glass can help to save energy. It is most obvious in the
case for insulating glass for windows and facades but also for less known products
such as weight-lightening reinforcement glass fibre used in automotive, aviation
and other transport modes to reduce the weight of vehicle and their fuel
consumption.
Save natural resources
Glass is a resource efficient material which is made of abundant natural raw
material such as sand and glass waste (cullets). Glass is a fully recyclable material
that can be recycled in close loop over and over again.
Safeguard people’s health and well-being
Glass is among the preferred materials not only for its aesthetics but also for its
own characteristics. Glass preserves taste and vitamins.
Sustainability & the Environment