Glass

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*************GLASS************
DEFINITION:


Glass is an amorphous (non-crystalline) solid material



A glass is defined as an inorganic product of fusion which has been cooled
through its glass transition to the solid state without crystallizing



Contains silica as their main component

INGREDIENTS:
SODA-LIME GLASS


Silica is the major ingredient of any glass



It has a glass melting point of over 2300 deg C



Pure Silica glass is used for special applications



Sodium Carbonate(in the form of soda ash) is added to lower the melting
point to around 1500 deg C



But soda makes the glass “water soluble” which is undesirable



Hence calcium oxide(obtained from limestone CaO),magnesium oxide and
aluminum oxide is added for the chemical stability



The resulting glass is called “soda-lime glass”



It contains about 70-75% of silica by weight



Soda-lime glass accounts for about 90% of manufactured glass

COMPOSITION
There are three classes of components for oxide glasses:
1. Network formers
2. Intermediates and
3. Modifiers

PROPERTIES



It absorbs, refracts or transmits light



It is extremely brittle



It has no sharp melting point



It has no definite crystalline structure



It is affected by alkalis.



It is available in various colors



It can take up a high polish and may be used as substitute for very costly
gems.



It is an excellent electrical insulator at elevated temperatures due to the fact
that glass may be considered as an ionic liquid.



It behaves more as a solid than most solids in the sense that it is elastic .



It is not usually affected by air or water



It is possible to obtain glasses with diversified properties. The glasses may be
clear, colorless, diffused and stained.



It is possible to weld pieces of glass by fusion.



It is transparent and translucent.



The glass panes can be cleaned easily by any one of the following methods.



Painting the glass panes with lime –wash and leaving it to dry and then
washing with cleaning water.

MANUFACTURING:
Broadly divided into following five stages
1. Collection of Raw Materials
2. Preparation of Batch
3. Melting in Furnace
4. Fabrication
5. Annealing
Collection:


Depending on types suitable raw material is collected



In addition,cullets and decolorizes are also added

Cullets:


Waste glass or pieces of broken glass



Increase fusibility of glass



Prevent loss of alkali by volatisation



Reduce the cost

Decolorizes:


Raw Materials like

USES:


The fiber glass reinforced with plastics can be used in the construction of
furniture, lamp shades, bathroom fittings, navy boats, aeroplanes , cars ,
trucks etc.



In the construction of modern homes, the walls and ceilings of hollow glass
blocks can be made. Cuts off the glare



Admits sunlight and controls sound and heat in a better way.



Color changing glass- a window with such glass will be transparent during day
time and it will be source of light during night.

SPECIAL TYPE OF GLASSES:
The following are the special types of glasses with modified properties:
1. Sheet glass
2. Plate glass
3. Safety glass
4. Tinte coated glass
5.



Glass Blocks

Soda lime (soda glass or soft glass glass-cheap, available in clean and clear
state.
o

Uses – manufacture of glass tubes , plate glass, window glass



Potash lime glass-hard glass, manufacture of glass articles



Potash lead glass- flint glass,
o



Uses – artificial gems, electric bulbs, lenses and prisms

Common glass-bottle glass

SPECIAL VARITIES OF GLASS
BULLET PROOF GLASS


Several layers of plate glass and alternate layers of vinyl resin plastic



Outer layers are thinner than inner layers



Thickness – 15mm to 75mm



It will not allow bullet to pierce through it

FIBER GLASS:


consists of two distinct materials,

1. a fibers of glass (ceramic), which is the reinforcement
and
2. a polymer resin called polyester, which serves as the
matrix


Minute glass rods that does not absorb water ,



Proof against fire.



Used in thermal insulations, sheets, fiber glass, reinforced plastics etc

GLASS REINFORCED PLASTIC (GRP):


Is a composite material or fiber reinforced plastic made of a plastic reinforced
by fine fibers of glass

FLOAT GLASS:


The molten glass coming out of the furnace is allowed to float on the molten
tin



Annealed to remove all the stresses



Used for smaller windows in domestic housing. Larger windows are made
from toughened glasses.



Allows the occupants to see out and at the same time allowing light in.
Commercial glazing



Float glass is becoming more and more popular in commercial applications.



Displays: based on its transparency, hardness and ease of cleaning, glass is
often used for display cases in retail outlets and countertops.

CLEAR FLOAT GLASS:


1)Smooth and flat surface



2) Excellent optical performance



3) Stable chemical properties



4) Resistant to acid, alkaline and corrosion.



5) Flexible size specifications, minimizing cutting loss



6) Substrata for each level of glass processing



7) Thickness: 2-19mm



8) Applications: architecture, mirrors, furniture, automobiles

REFLECTIVE FLOAT GLASS:
1) CVD coated tinted glass
2) Can be for tempered, hot curved and
laminated
3) Width: 5mm 4) Size: 1,200 x 900 – 3,300 x
6,000mm 5)
4) Applications: walls, doors, windows, indoor
decorations
LOW E-GLASS:


Low emissivity (low e) is a quality of a surface that radiates, or emits, low
levels of radiant energy,



Emissivity is the value given to materials based on the ratio of heat emitted
compared to a blackbody, on a scale of 0 to 1



To make low-e glass, certain properties such as the iron content may be
controlled



Specially designed coatings, often based on metallic oxides, are applied to
one or more surfaces of insulated glass.



These coatings reflect radiant infrared energy, thus tending to keep radiant
heat on the same side of the glass from which it originated,



It allows visible light to pass.

FOAM GLSS:


Prepared in the form of rectangular glass blocks



Finely ground glass and carbon are mixed and melted to get foam glass



During melting it expands and assumes form of a black foam



Contains more than 350 million inert air cells per cu.m



Foam glass can float in water



Can be cut like wood



Fire-proof, rigid and an excellent heat insulator.



Can be a substitute for cork in refrigeration industry

GLASS BLOCK


Partially evacuated and completely sealed hollow units which are
formed by fusing together two – halves of pressed glass.



Sq sizes – 150mm, 200mm and 300 mm



Thickness -100mm


Faces of the blocks are
suitably treated to obscure
the glass and to diffuse
light. These blocks possess
high insulating value and they are
set in cement motor.

Advantages


They are easy to clean



Excellent light transmission



Very good insulation against cold



Heat and noise.



Glass brick, also known as glass block, is an architectural element made from
glass. Glass bricks provide visual obscuration while admitting light.



Used in the early 1900s to provide natural light in industrial factories.



Installing glass bricks is in a cement based mortar.



These mortar joints are reinforced with stainless steel rods of 5-6 mm
diameter horizontally and vertically to improve both the strength of the
glass brick panel and to help achieve fire resistance where required.



Most glass bricks require a 10-15 mm mortar joint to accommodate any
minor irregularities in the alignment of the.



Specially shaped plastic spacers within the mortar joints to enable the
panel to be constructed more quickly and accurately.



Provision must be made when installing glass blocks to allow for differential
thermal expansion of the glass.



This is normally achieved by installing a ‘sliding’ joint at the base of the panel
and the inclusion of a compressible packing strip at the panel’s abutments
with the jambs and head.



Panel’s perimeter are packed with a compressible material usually a
polythene foam

Heat Excluding Glass:


This glass allows light to pass thro it but it eliminates heat. It is used in
windows of coaches of higher class in railways, in window panels of important
buildings.

Obscured Glass



Used at places where light is to be transmitted and vision is to be obscured.



Uses – public toilets , office doors, partitions etc



Figured glass, corrugated glass

Perforated Glass


Perforations are made in sheet glass with the help of rollers panels in
ventilators.

Safety Glass:


They area shatter proof glass



Glass is formed by placing celluloid between two sheets of the plate glass and
then applying glue to make a single unit



They do not fall apart when broken

Shielding Glass


Special variety of glass and it contains heavy elements like lead oxide.



Windows – high radiation is observed

Ultra Violet Glass


This glass transmits effectively ultraviolet rays even though it is not in the
direction of sun.



Uses – windows of schools and hospitals

STRUCTURAL GLASS


Glass – crete squares or lenses which are set in cement concrete and
reinforced with steel frames- glass bricks-light structural members also,
pavement lights, partitions. Lantern lights etc.



Stair and upper landing with glass beam support

WIRED GLASS:


Wired glass is float glass which has been formed with a layer
of fine wire mesh in the centre of its cross-section.



This layer of mesh is visible when the pane of glass is looked
through. Wired glass is very strong and is used for security
purposes and also in locations where safety is a concern.



Steel wire mesh is placed in glass during rolling operation



Wired glass – roof, skylights, fire resisting
doors and windows

LAMINATED GLASS
It is actually two layers of glass sandwiching a thin plastic sheet.
One or both of these layers of glass may be tempered. The middle plastic sheet
serves to hold the overall glass sheet assembly together when broken.
Laminated glass is used in automotive windshields and in buildings where safety is
a concern
INSULATING GLASS (IG)
Glass units are hermetically sealed combinations of two or more tiles of glass
separated by a dry airspace. IG units improve thermal performance, significantly
reducing heating and air conditioning costs. IG units also reduce interior
condensation in cold climates.

A wide range of applications include:
Fixed and Operable windows
Storefronts and Curtain Walls
Sloped/Overhead Glazing
Non vision (Spandrel) Locations
HEAT TREATED GLASS
Heat-treated glass is glass that has been processed through a tempering oven to
increase its strength to resist impact, mechanical loads and thermal stress
breakage.
There are two distinct heat-treated glass products,
1. heat-strengthened
2. Fully tempered.
APPLICATIONS:


Doors: Patio, Entrance, Storm and Sidelites



Tub and Shower Enclosures



Windows: Commercial/ Residential, Fixed and Operable



Displays, Partitions



Storefronts and Handrails

LAMINATED GLASS
It is a multifunctional glazing material that can be used in a variety of applications.
It is manufactured by permanently bonding two or more tiles of glass with layers of
polyvinyl butyric (PVB) interlayer, under heat and pressure, to create a single
construction
APPLICATION:


Sloped/Overhead Glazing



Museums, Prisons, Government Buildings



Jewelry Stores, Banks, Airports



Safety Glazing Applications



Schools, Hospitals, Hotels



Interior Partitions, Office Buildings

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