Glass is made from silica and other additives like soda ash and lime. Modern glass uses sand, soda ash, and limestone. Different colors are achieved by adding metal compounds like cobalt for blue. The float glass process involves floating molten glass on liquid tin to create flat sheets. Float glass makes up most flat glass products and is made in thicknesses from 2-25mm. Non-sheet glass includes cast glass blocks and profiled sections. Sheet glass undergoes further processing like annealing, toughening, laminating, etching, and adding coatings. Structural glass elements use toughened glass in columns, fins, and load-bearing walls fixed with clamps or adhesive.

1. GLASS, ITS TYPES
LECTURE # 6

2. Glass and its brief history
 Glass is a blend of metallic oxides, primarily Silica.
 Silica does not crystallize when cooled from liquid to solid and is non crystalline and
amorphous. That gives rise to the transparency of glass.
 Early glass was made from Sand, Soda Ash, & Lime that was used to glaze stone beads
5000 years ago by Egyptians. Later it was used to make glass beads in 2500 BC and then
into long hollow vessels by 1500 BC.
 For many centuries it has been worked out by drawing molten material from furnace and
than rolled out pressed into appropriate moulds which were later fashioned by cutting and
grinding.
 In Medieval Era Potash was added instead of soda ash with increase quantity of Lime that
give birth to the less durable glass that is the cause of deterioration of some church glass in
that period.
 The various colors in glass were obtained by adding different metal compound to the melt.
Cobalt was added to give blue color. Copper produced Blue or Red. Chromium produced
green.
 In fifteenth century white opaque glass was produced by addition of tin or arsenic.
 Clear Glass could only be obtained by adding manganese or antimony as a decolorizer to
remove green colorization due to presence of iron impurities within the sand

3.  With the advent of Fully glazed facades by the late 20th century ; the construction
industry has become major consumer of glass and acted as a proactive force in
the development of new products.
 COMPOSITION: Modern Glass is manufactured from Sand (Silica) , Soda Ash
(Sodium Carbonate) & Lime stone (Calcium Carbonate) along with other
additives..

4. Manufacture of Float Glass
FLOAT GLASS: The term "float" refers both to a type of glass and to the process by which
it is made.
Float glass is the basic glass from which almost all the flat glass products are derived. It
may be clear or colored, and is produced in large sheets that are normally processed
into secondary products.
The float process involves literally floating the molten glass on a bath of liquid tin,
producing a perfectly flat surface on both sides.
The raw materials for float glass are 73% sand (silicon dioxide), 15% soda (sodium
carbonate), 10% limestone (calcium carbonate) and 2% various additives.
MANUFACTURING PROCESS
 A furnace produces a continuous supply of molten glass at approximately 1100 C.
 It flows across the surface of a large shallow bath of molten tin in presence of
hydrogen and nitrogen which prevents oxidation of molten metal.
 The glass ribbon moves across the molten metal initially at high temperature for
irregularities on both surfaces to become evened out leaving a flat and parallel
ribbon of glass. It solidifies at 600C.

5.  Any further residual stresses are removed as glass passes through the annealing lehr
leaving a fire polished material
 The glass is washed then.
 Thickness of glass is controlled by the speed it it is drawn from the molten bath
 The float glass made for construction industry is made within the thickness range of
2-25mm.

6. Non-Sheet Products
NON SHEET PRODUCTS
Non Sheet Products are those products that are made
directly without the formation of sheet. It includes the
following products.
CAST GLASS: Glass may be cast and pressed in to shapes
for glass blocks and extrude sections
 Glass Blocks: Glass blocks for non-load bearing and
partition walls are manufactured by casting two half
blocks at 1050C And joining them together at 800 C
and followed by annealing. The Standard blocks are
115, 190, 240 and 300 mm Square with 80 and 100 mm
thickness. These blocks can be joined with mortar that
gives fire resistance of 60 mins

7. PROFILED TROUGH SECTIONS:
 Profiled trough sections are available in different sizes that can be used horizontally
or vertically with single or double glazing
 Silicon sealant is used to conceal the joints

8. Sheet Products
 The standard thickness for float glass are 3, 4, 5, 6, 8, 10, 12, 15, 19 and 25 mm And
the sheet sizes available in Pakistan are 4’-0” X 8’-0” and 5’-0”X 10’-0”
 Although the maximum sheet size available is 3 X 12 m in other European countries

9.  Annealed glass: Annealed glass is the basic flat glass product that is the first result of the
float process. It is common glass that tends to break into large, jagged shards. It is used
in some end products and often in double-glazed windows. It is also the starting material
used to produce more advanced products through further processing such as
laminating, toughening, coating,
 Toughened glass/Tempered Glass: Toughened glass is treated to be far more resistant to
breakage than simple annealed glass and to break in a more predictable way when it
does break, thus providing a major safety advantage in almost all of its applications.
Toughened glass is made from annealed glass treated with a thermal tempering process. A
sheet of annealed glass is heated to above its "annealing point" of 600°C; its surfaces are
then rapidly cooled while the inner portion of the glass remains hotter. The different cooling
rates between the surface and the inside of the glass produces different physical
properties, resulting in compressive stresses in the surface balanced by tensile stresses in the
body of the glass.
These counteracting stresses give toughened glass its increased mechanical resistance to
breakage, and are also, when it does break, what cause it to produce small, regular,
typically square fragments rather than long, dangerous shards that are far more likely to
lead to injuries. Toughened glass also has an increased resistance to breakage as a result of
stresses caused by different temperatures within a pane.
Toughened glass has extremely broad applications in products for both buildings and,
automobiles and transport, as well as in other areas. Car windshields and windows, glass
portions of building facades, glass sliding doors and partitions in houses and offices, glass
furniture such as table tops, and many other products typically use toughened glass.
Products made from toughened glass often also incorporate other technologies, especially
in the building and automotive and transport sectors.

10.  Laminated glass: Laminated glass is made of two or more layers
of glass with one or more "interlayers" of polymeric material
bonded between the glass layers.
Laminated glass is produced using one of two methods:
1. Poly Vinyl Butyl (PVB) laminated glass is produced using heat
and pressure to sandwich a thin layer of PVB between layers of
glass. On occasion, other polymers such as Ethyl Vinyl Acetate
(EVA) or Polyurethane (PU) are used. This is the most common
method.
2. For special applications, Cast in Place (CIP) laminated glass is
made by pouring a resin into the space between two sheets of
glass that are held parallel and very close to each other.
Laminated glass offers many advantages. Safety and security are
the best known of these, so rather than shattering on impact,
laminated glass is held together by the interlayer. This reduces the
safety hazard associated with shattered glass fragments, as well as,
to some degree, the security risks associated with easy penetration.
But the interlayer also provides a way to apply several other
technologies and benefits, such as coloring, sound dampening,
resistance to fire, ultraviolet filtering and other technologies that
can be embedded in or with the interlayer.

11.  Mirrored glass: To produce mirrored glass, a metal coating
is applied to one side of the glass. The coating is generally
made of silver, aluminum, gold or chrome. For simple
mirrored glass, a fully reflective metal coating is applied
and then sealed with a protective layer. To produce "one-
way" mirrors, a much thinner metal coating is used, with no
additional sealing or otherwise opaque layer.
Mirrored glass is gaining a more prominent place in
architecture, for important functional reasons as well as for
the aesthetic effect.
 Patterned Glass: Patterned glass is flat glass whose
surfaces display a regular pattern. The most common
method for producing patterned glass is to pass heated
glass (usually just after it exits the furnace where it is made)
between rollers whose surfaces contain the negative relief
of the desired pattern(s).Patterned glass is mostly used in
internal decoration and internal architecture. Today, it is
typically used for functional reasons, where light but not
transparency is desired, and the patterns are accordingly
subtle. However, it has also at times been fashionable as a
design feature in itself, in such cases often displaying more
prominent patterns.

12.  Decorative Etched/ Sand Blasted Glass: Acid
Etched glass is available in all thicknesses of glass
these glasses have low obscuration factor and
should not be used in area of high humidity, as
condensation or water causes temporary loss of the
pattern. Etched glass should be handled with care
at site as grease, oil and finger marks are difficult to
remove completely. Etched glass may be
toughened and laminated.
 Similar visual effects can be achieved by sand
blasting techniques although the surface finish is
less smooth. Pattern may be clear on a frosted
background or the reverse depending on the
aesthetic effect and level of privacy required

13.  Extra clear glass: Standard float glass is
slightly green due to the presence of iron
oxide impurities within the key raw material
sand. However, clear white glass can be
produced, at a greater cost by using purified
ingredients. The light transmittance of clear
white glass is 2% greater than standard float
glass. Clear White glass is colorless at edges.

14. Structural Glass
 Glass columns are frequently used as fins to restrain excessive deflection caused by
wind and other lateral loads to glass facades.
 The fixing between the glazing and columns is done through SS Clamps bolted
through performed holes before applying any coating or toughening, although
silicone adhesive can also be used. Silicon adhesive is only structural adhesive that
is suitable for glazing units.
 Typically a storey height fins are used that are connect with the floor through
aluminum/ SS shoe.
 Toughened glass is strong in compression therefore an appropriate material for load
bearing columns and walls

15. Clamps
for
holding
glass