GLASS Presentation, GORUP 6

8/9/2019 GLASS Presentation, GORUP 6

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PRESENTATION GROUP 6

GLASS


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THIS TOPIC INCLUDES

Introduction

Constituents

Manufacture process

Classication

Commercial forms


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GLASS Defnition and Introduction

Glass:is an amorphous substancehaving homogeneous texture.

The most common types used inbuilding construction are sheet,plate, laminated, insulating, andpatterned glass.


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!EHA"IOR O# GLASS

The expansion and contraction of thematerial is minimum.

Brittle

Hard

Transparent

Chemically inactive in high temperature.

o! electric conductivity

"esistance to corrosive action of gas.


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CONT$

Most ordinary colorless glasses are #l$ali%ime,silicate and al$ali%lead silicate !ith tensile andcompressive strength of about &'%(')*mm+and ''%-''')*mm+.

The strength is very much aected by internaldefects.

The main shortcoming of glass is its brittleness.


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Constituents o% Glass

The ra! materials used inmanufacturing

glass are/%

0ilica

ime

0oda

1otash

ead 2xide and


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CONTD$

Cullet

3 Iron is not describe as a constituent4ho!ever, !hen present it imparts abottle green color to the glass.


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CONSTITUENT O# GLASS

Silica/% is used in the form of pure5uart6, crushed stone, sand stone andpulveri6ed 7int, should be free from

iron contents for best 5uality glass.

0ince it melts at very high temperature

8--'9c: carbonate of sodium orpotassium are added to lo!er do!nthe fusing temperature at about ;''9c.


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CONTD$

Li&e/% is used in the form of lime stone,chal$ or pure marble.

The addition of lime ma$es the glass 7uidand suitable for blo!ing, dra!ing, rollingand pressing and spinning.


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CONTD$

Soda/% act as an accelerator for thefusion of glass and an excess of it isharmful.

Potas'/% renders glass infusible andma$es glass re resistance


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CONTD$

Lead o(ide/% imparts color,brightness and shine.

=hen ->%&'? of it added tosubstitute lime is lo!er the meltingpoint.

Imparts good !or$ability, !hile itstransparency is lost !ith the glassbecoming brittle and crystalline.


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CONTD$

Cullets/% are bro$en glasses addedto act as a 7ux to prevent loss ofal$ali by vitali6ation during the

process of forming glass and also tolo!er the fusion temperature.

It may reduce the resistance of glassto chemical attac$.


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THAN) *OU

NE+T :CLASSI#ICATION

O#GLASS


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,ELL CO-E TO

CLASSI#ICATIO

N O# GLASS


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Cont.

The classification of glass can be discussedbased on its chemical constitutesandcommercial form that the glass can exist.

Based on its constitutes its classified as

soda-lime glasslead glass and

boro-silicate glass.


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1.soda-lime glass

it is also known as soda-ash glass, soda glass orsoft glass.

obtained by fusing a mixture of silica, limeand soda

The quality of this glass can be improved by

adding aluminaand magnesium oxide

and then called crown glass.

This is the most common type of glass used in doors,

windows

for making glass-waressuch as bottles.


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2.Lead glass

also $no!n as .int /lass

is obtained by fusing a mixture ofsilica,leadand 0otas' .

It is free from iron i&0urities1 Lead /lass 'as 'i/' s'inin/ a00earance

and can ta2e 0olis'1

It is not a3ected 45 te&0erature1

Electric 4ul4s o0tical /lasses cut /lassorna&ental /lass 7or2s and radio 8al8esare so&e o% t'e 0roduct o% t'ese /lasst50e1


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3.Boro-silicate glass

is obtained by fusing a mixture of silica,borax, lime and felspar.

The examples are pyrex glass and heatresisting glass.

Boro silicate glass can withstand hightemperatures and is most suitable formaking laboratory equipment andcooking utensils


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,ELL CO-E TO

-ANU#ACTUREO# GLASS


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Manufacture of glass

@lass is manufactured in the follo!ing four steps/

91-eltin// The ra! materials A lime, soda andsand A separately cleaned, ground, sieved 8calledBatch: in denite proportion and mixed !ith

!ater are fused in a continuous type 8tan$:furnace or batch%type 8pot: furnace.

The charge in the rst stage melts, forming abubbly, stic$y mass, and as the temperature is

raised 8--''D CE-F''D C: it turns to a more!atery li5uid and the bubbles rise to the surface.


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The melting process in case of

ordinary soda%glass involves thefollo!ing series of reactions/

CaC2&G0i2F Ca0i2& G C2F

)aFC2& G 0i2F )aF0i2& G C2F

=hen all the carbon dioxide hasescaped out of the molten mass,

decolori6es such as Mn2F or niter areadded to do a!ay !ith ferrouscompounds and carbon.


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The coloring salts are added at thisstage. Heating is continued till themolten mass is free from bubbles

and glass balls. #s the glass cools8;''D C:, it is ready to be dra!n or7oated to its desired thic$ness and

si6e at the other end of the furnaceas sho!n by a 7o! diagram inig.->.-.


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F. Molting and shapingprocess

The molten glass can be fabricatedto desired shapes by any one of thefollo!ing methods/


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a. Blo!ing /blo!ing # F m long and -F

mm diameter blo! pipe is dipped inthe molten glass and ta$en out. It isheld vertically and is vigorouslyblo!n by the operator. The stic$ingmolten glass ta$es the shape of ahollo! ball. 2n cooling it is reheatedand the blo!ing operation repeated a

number of times till the desiredarticles are ready.


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41 #lat dra7in/1The process of dra!ing theglass up into a sheet begins !hen an grille

8bait: is lo!ered into the glass in the $iln. In ashort time the li5uid molten glass adheres tothe bait, and as the bait is slo!ly lifted it dra!sa sheet of glass. The bait and the dra!n sheet

of glass are then dra!n through rollers, the baitis crac$ed o and a continuous sheet of glass isdra!n up. This sheet is then slo!ly cooled in achamber and annealed for cutting into propersi6e. # machine for vertical dra!ing of glass issho!n in ig. ->.F.


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c. compression molding / In this

process moulds are used to obtain thearticles of desired shapes.

d1 S0innin/1 # machine is used to spin

the molten glass. The bres so producedare very ne and are used for heat andsound insulation.

e1 annealin/ @lass articles are allo!edto cool under room temperature bypassing through dierent chambers !ithdescending temperature.


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If cooled rapidly, the glass being badconductor of heat, the supercial

layer cools do!n rst and straindevelops in the interior portions,!hich causes une5ual expansion and

the articles are li$ely to crac$.

fnis'in// #fter annealing the

glass articles are cleaned, ground,polished, cut and sand blasted.


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,ELL CO-E TO

CO--ERCIAL#OR- O# GLASS


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Commercial form of glass

-. 0heet glass/ is used for gla6ing doors,!indo!s and partitions and is obtainedby blo!ing the molten glass into the

shape of a cylinder. The ends of thecylinder so produced are cut a!ay andthe cylinder is 7attened over a planetray. It is available in thic$nesses of F,F.>, &, , >, >.> and (.> mm and up to->' J --'' mm si6e and is classied as


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CONTD$1

a.2rdinary gla6ing 5uality /@eneral engineering purpose

b.0elected gla6ing 5uality /Class !or$s

c.0pecial selected / 5uality0uperior 5uality !or$s such assho! cases and cabinets etc.


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F. 1late glass

% 1late glass/ is used for allengineering purposes and is superiorto sheet glass.

# plate glass diers from a sheetglass in that it has a parallel,distortion%free surface obtained by

grinding or 7oating process. It is produced by pouring the molten

glass on casting tables and leveling

it to an uniform thic$ness. Both the


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&. Tempered glass

is made from plate glass by reheatingand sudden cooling and is & to > timesstronger than plate glass.

#lthough not unbrea$able, it resistsbending stress better than plate glassand, !hen bro$en, the pieces are

relatively small in si6e. It is usedextensively in sports arenas, slidingdoors and curtain !alls.


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. =ired glass

is produced by embedding !ire nets '.( to '.>(mm into the centre of sheet glass during casting.

The minimum thic$ness of !ired glass is ( mm.=hen bro$en it does not fall into pieces.

It has higher melting point than ordinary glass.

=ired glass is used for re resisting doors and!indo!s, for s$y lights and roofs.

# special example of this is !ired%refrax glass!hich transmits -'' per cent more light than theother glasses.


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>.2bscured glass

is made comparatively opa5ue to sunlight.

#lso $no!n aspatterned glass.

They are classied as frosted, rolled and ribbed.

a. rosted glass/ is produced by subjecting the

polished face of the glass to a sand blast which grindso the surface. It can also be produced by etching onglass by hydro7uoric acid.

b. rolled glass/ has a series of !aves of desired pattern

on the surface and is also $no!n as gured rolledglass.

c. ribbed glass: # series of triangular ribs are producedin the glass during casting.


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d d f


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.Heat and sound proofglasses

T!o or more glass plates aresand!iched by a tinted plastic innerlayer.

It provides high resistance to heatand glare.

By increasing the thic$ness of plastic

layer the glass can be made moresound resistant.


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;. Bullet proof glass

is produced by placing vinyl plasticand glass in several alternate layersand pressing them !ith outer layers

of glass. It is used in ban$s, Le!ellery stores

and display !indo!s.


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K. Insulating glass

is composed of t!o glass plates into!hich a layer of (E-& mm thic$dehydrated air is sealed.

The round edges are formed byfusing together the t!o glass plates.

These glasses reduce the heat

transmission by &'E(' per cent.


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-'. Heat absorbing glass

is bluish green in color and cuts ultraviolet rays of sun.

The example is calorex.

It is used in railway carriages,factories, hospitals, health clubs andkitchens.


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--. @round glass

In this type of glass one face of plateor sheet glass is made rough bygrinding.

It is used for maintaining privacy byobstructing vision and at the sametime allo!ing light.

The ground glass is used forbedrooms, toilets and for ma$ingblac$ boards.


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-F. Bloc$ glass

is hollo! sealed made by fasteningtogether t!o halves of pressed glass.

It is used for ma$ing partitions.


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-&. 2ptical glass

contains phosphorus, lead silicateand a little cerium oxide, the lattercapable of absorbing ultraviolet light

inLurious to eyes. They are used for ma$ing lenses.


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THAN) *OU

THE END

GLASS Presentation, GORUP 6

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