Ma’am Aasia Farrukh
Faheem Abbas (22)
Saeed Akhter (23)
Rafique Khan (03)
Muhammad Zubair (19)
Muhammad Mohsin (39)
Abbas Khattak (40)
Syed Imad Zakir (56)
Wah Engineering College, Wah Cantt.
Composition of glass
Few properties of glass
Method of manufacturing
Process flow diagram
Types of glass
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• This Material is made by Pliny.
• While cooking a meal in a vessel placed
• accidently upon a mass of trona at the seashore.
• In early 6000 or 5000 B.C the Egyptians were making sham jewels of
• Window glass is made in 290 A.D
• The Hand Blown glass is made in 12th century.
• Glass works is funded in USA in1608 at Jamestown.
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Glass may physically be defined as a rigid, undercooled liquid having no definite
melting point and a sufficiently high viscosity greater than 10^12 Pa.s to prevent
Glass is chemically defined as the union of the non volatile inorganic oxides resulting
from the decomposition and fusion of alkali and alkaline earth compounds, sand and
other glass constituents, ending in a product with random structure.
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Formation of Silica Sand
Mechanical and chemical weathering of quartz being igneous and
Less stable minerals break down to become silica sand.
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Formation of Soda ash
Erosion of igneous rock from sodium deposits. Transport
by waters as runoff and collect in basins when sodium comes in contact
with CO2 precipitates out sodium carbonate.
Chemically soda ash is
obtained by Solvay process
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Includes hydrated Ca(OH)2 and quick lime CaO. Only quick lime can be used
to make glass.
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Composition of the Glass
1.Soda lime glass:
Soda lime glass constitutes 95% of all glass manufactured.
SiO2 70 to 74% ,CaO 8 to 13% , Na2O 13 to 18%
2. Lead glass:
These glasses are of very great importance in optical glass.
SiO2 67% , As2O 0.5%, CaO 0.9% , Na2O 9.5% , K2O 7.1% , PbO 14.8%.
3. Borosilicate glass:
B2O3 10 to 20% , Silica 80 to 87% , less than 10% Na2O
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Properties of glass
Following are the properties exhibited by glass.
1. Capacity to absorb different colors without effecting transparency.
3. Chemically inert.
4. High refractive index
7. Transparency and translucence
10. Electrical insulators.
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In condensed matter physics, an amorphous (meaning without shape or
form) or non crystalline solid that lacks the long range order characteristic
of a crystal.
A material is brittle if, when subjected to stress it breaks without
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TRANSPARENCY AND TRANSLUENCE:
In the field of optics, transparency is the physical property of allowing light to pass
through materials; translucency allows light to pass through diffusely.
Capacity to absorb different colors without effecting transparency
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In optics dispersion is the phenomenon in which phase velocity or a wave depends
upon its frequency or alternatively when the group velocity depends on the frequency.
Media having such a property are termed dispersive media.
In a prism, material dispersion causes different colours to refract at different angles
splitting white light into a rainbow.
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It is a word (from Latin vitrium “glass” via French vitrifier) is the deformation of a
substance into a glass. Usually, it is achieved by rapid cooling a liquid through the glass
transition. Certain chemical reactions also result in glasses.
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Following are the raw materials.
2. Soda ash: Forms basic part of glass
3. Sodium nitrate: Accelerates melting
4. CaO: Forms the basic part of glass.
5. Silica: Forms acidic part of glass.
6. Barium sulphate: remove impurities in the form of scum.
7. Feldspar: Retards de-vitrification.
8. Potassium oxide: Used as a softening agent.
9. Borax: Increase hardness or refractive index.
10. Boric oxide: Improves chemical or corrosive resistivity.
11. Phosphoric oxide: To impart bright appearance.
12. Lead oxide: Increases insulation.
13. Selenium: Used as decolorizer. 28/05/2k14 15Wah Engineering College, Wah Cantt.
FOLLOWING ARE THE STEPS FOR THE MANUFACTURING OF GLASS:
2. SHAPING AND FORMING:
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Based on the type of the glass suitable glass manufacture materials are
selected. Raw materials are reduced in size by crushing and grinding. Raw
materials are now subjected to melting in furnace.
For special glasses like optical glass. Raw materials are melted in pot furnace
made of ceramic material capacities varying from 1-2 tons and is used for
small production batches
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Molten glass is obtained by melting the raw materials in 1350-1400 ton capacity
regenerative tank furnace and can be used in continuous processes. During melting of
raw materials various reactions occur at various temperatures.
Chemical reactions :
Na2CO3 +aSiO2 Na2O.aSiO2+CO2
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SHAPING OR FORMING :
Glass may be shaped by either machine or hand molding. The outstanding factor
to be considered in machine molding is that the design of the glass machine should be
such that the article is completed in very few seconds. During this relatively short time
the glass changes from a viscous liquid to a clear solid. The design problems like flow
of heat, stability of metals, and clearance of bearings should be solved.
• Fourcault process window glass
• Colburn process window glass
• Continuous automatic process plate glass
• Float process float glass
• Glass blowing bottles, light bulbs, tubing
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To reduce internal stresses; in annealing oven.
• Walls are comparatively thick and cooling will not be even.
• The inner and outer skins of a glass become rigid.
• The still contracting inner portion build up internal stresses.
• Uneven cooling develop substantial stresses in the glass.
• Glass passes through a lehr after removal from the blow mold.
• Lehr is a belt passing through the controlled temperature oven of about 200mm-300mm
per minute. Glass temperature is raised to 565 *C and then gradually cooled to room
temperature with all internal stresses reduced to safe level in about an hour as they exit.
• Improperly annealed glass are fragile and high breakage.
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All types of annealed glass must undergo certain finishing operations, which are
simple and important. These include:
• Grading etc.
Although these are not required for every glass object, one or more is almost
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• Pilkington Brothers in England it employs the tank furnace melting
• Molten glass passes through narrow canal which connects furnace and
• Rate of flow is controlled by gate that spans the canal
• controlled heating melts irregularities and produces both sides flat
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• The Danner process was developed for the continuous production of
glass tubing and rods
• Glass flows from a furnace in the form of a ribbon, and passed
through a revolving hollow pipe inclined at 30⁰
• Glass flows and air is blown to form a tube, a belt pair grip it and
draw it at uniform speed
• Temperature, speed of drawing, volume of air blown control the dia
and wall thickness of tube
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• "ribbon machine" is used for the process
• ribbon of glass is passed along a conveyor belt, heated in a furnace
• then blown by air nozzles through holes in the conveyor belt into
• Bulb envelope is formed
• The filament and its supports are assembled on a glass stem, which is
fused to the bulb
• the air inside the bulb is evacuated, and the casing is filled with an
argon and nitrogen mixture.
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Fused Silica Glass:
• May be made by pure silica.
• Manufactured by Corning by high temp pyrolysis of SiCl4.
• This process lends itself naturally to controls which permit chemically
• The raw silica produced in the form of plates or boules.
• The high temp give pure glass with low contaminants with ratio of
• It have lowest ultrasonic absorption of any material.
• It have low thermal of expansion that is why this is used in telescopes.
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High Silica Glass:
• This is also known as Vycor.
• It is imp and advance in production of fused silica in composition and
• The product contain 96% silica, 3% boric oxide and rest is alumina and
• Borrosilicate glass compositions of about 75% silica content in which
glass is melted and molded. After cooling the articles are subjected to
heat treatment and annealing which is induce the glass to separate
into tow distinct phases.
• One phase is High in boric and alkaline so dissolve in hot acid soln.
• Second is rich in silica and insoluble in those soln.
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Decorated and Colored Glass:
• Transparent colored glass are essential for science and technical use.
These are three types;
a). Color is produced by the absorption of certain light frequencies by
agent in solution of glass.The coloring agents are oxides of Ti, V, Cr, Mn,
Fe, Co, Ni, and Cu.So NiO dissolved in sodium lead glass yields brown
b). Color is produced by colloidal particles ppted within an originally
colorless glass by heat treatment. Example, ppt of colloidal gold
producing gold ruby glass.
c). Color is produced by microscopic particles which may be colored
themselves, as selenium reds (SeO2) used in traffic lights.
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• This is grouped into two types;
1). Laminated glass:
It consists of two sheets of thin plate glass of 3mm
thickness whit center of non-brittle plastic material. They are washed
and an adhesive material is applied to the glass under moderate pressure
2). Tempered Glass:
This is very strong and used in doors and window of
vehicles. It possesses high internal stresses. Its manufacturing involves
controlled heat annealing whereby the uniform stresses in glass are
replaced by controlled, uniform, low-level, stress.
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• A special glass, low in silica, is used for the production of fibers.
• Efforts have been made to produce a fiber for the reinforcement of
concrete that would not be attacked by and weakened by alkali.
• The most successful of these alkali-resistant fibers are made from
glass containing 17% ZnO.
• This is very expensive.
• This is also difficult to produce.
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Applications and Uses of Glass
Tableware (drinking glasses, plate, cups, bowls)
Housing and buildings (windows, facades, conservatory, insulation,
Interior design and furniture (mirrors, partitions, balustrades, tables,
Appliances and Electronics (oven doors, cook top, TV, computer
Glass is used in the following non-exhaustive list of products:
Packaging (jars for food, bottles for drinks, flacon for cosmetics and
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Automotive and transport (windscreens, backlights, light weight but
reinforced structural components of cars, aircrafts, ships, etc.)
Medical technology, biotechnology, life science engineering, optical
Radiation protection from X-Rays (radiology) and gamma-rays
Fe optic cables (phones, TV, computer: to carry information)
Renewable energy (solar-energy glass, windturbines)
All of this is made possible by the countless properties of the glass
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