Analysis of Glass


What is Glass ?
Glass is a hard amorphous (it is neither solid nor liquid but exist in various stage) material normally fragile and transparent ,that we use commonly. It is mainly compound of solid (Silicates SIO2)  and Alkali (Base).
At high temperature when materials use together,which then cooled rapidly that no crystalline regular lattice is formed.
With the application and usage in mind the composition of glass and lie cooling rate is rated accordingly to obtain the desired specific properties.

Common Ingredients : 

  • Solid SIO2 (Silica) and Polymer (SIO2)n is used.
  • Sodium carbonate (Soda Ash) Na2Co2


By adding Soda ,the melting point of sand is reduced to 1000OC . Normal saffening point of SIO2 .Is up to 20000C , however degradation starts at 17190C and molecules tend to move freely, Soda ,when added ,makes glass water – soluble soft and not durable.

  • Lime Stone Calcium Carbonate (COCO2) or Dolomite (MgCO2) Magnesium Carbonate


This is naturally found compound known as lime. It is also found in the form of Marble and Chalk.

The purpose of adding lime is to increase the hardness and durability of glass and to make it insoluble in water. Common glass contain 70% amorphous Silicon Dioxide (SIO2) ,This is also known as Soda Lime Glass

  • Other Oxides and Additive are added to get specific properties to get different colours and effects.


There are three main types of Glass.

  • Soda Lime Glass
  • Lead Glass
  • Brosilloats Glass 
  • Soda Lime Glass :

             As explain above .it is the most commonly use glass. It  contains 60% - 75% Silica ,12% - !8% Soda and 5%- 12% Lime . Soda Lime Glass is not resistant to High Temperature, Sudden Thermal Changes and Corrosive Chemical.

Usage :
            Mainly Window Glass, Bottles ,Drinking Glasses, Flower Pots etc.


  • Lead Glass  :

It has high percentage of Lead Oxide (about 20%).

It is soft surface glass suitable for decorative glass. This glass can be subjected to Grinding ,Engroving ,Drllling etc. Lead Glass has a High Refractive Index giving high brilliance to glass.
This glass is not suitable for High Temperatures and sudden Temperature variations.
When the content of PBO is less than is known as ‘Crystal Glasss’.
Addition of Lead in Moderate amounts to Soda Lime Glass increase durability .whereas, in percentage , it low melting  point and decrease the hardness giving the soft surface to glass.

Usage :
            Radiation helding Glass ,Nuclear Park, Decorative Articles and Crystal Glass.


  • Brosilicate Glass :

It a glass having at least 5% Boric Oxide. It has higher Chemical Resistivity and Chemical Corrosion is also slow,

Usage :

            Laboratories ,Chemical Plants ,Ampluse and Viats in Pharamceutical Industries .Electric Bulbs etc. It is used to make Cook ware. Heat Resistant terms are made with Boro Silicate Glass.


  • It is a solid and hard material.
  • Amorphous  structure.
  • Transparent to visible light.
  • Fragile and easy to break small pieces
  • Almost inert to most chemicals.
  • 100% Recyclable.
  • Biologically Inactive.


However, these properties can be changed by addition of other compounds or heat treatment.

Other additives added to change the colour of glass are Metal and Metal Oxides.

  1. Iron (IO2) Oxide : Bluish Green Glass, Add Chromium   : Red Green Glass.
    Used in making bottles in Wine and Beer industries.
  1. Sulphur :Used with Carbon and Iron PolySulphides Amber Colour Glass.More addition can result in Yellow to Black Glass.
  1. Manganee Can remove Green Colour tint due to Iron. It gives puple Colour.
  1. Selerium  Small Quantities are used to decorative glass. Large quantities give Pink to Reddish Colour. Add Cadmium Sulphide for Brilliant Red Colour. This Glass is Called Selerium Rub.
  1. Cobalt Added to give Blue Glass. The result are very good if it is Potash Glass.
  1. Copper Oxide Added to give Turquiose Colour.
  1. Pure Copper Metal to get Dark Reds Colour, Almost OPAQUE Glass, Also called “Ruby Red Glass”.
  1. Metal As the concentration increases colour firm Blue to Voilet to Black is obtained.However Nihol and Cobalt is used to  “Decolourise Lead Glass”.
  1. The Oxides Antromany and Arsenio Oxides.Added to make “White Glass  looks likes POROCELEAN.
  1. Chromium with Tin Oxide and Amonio Added to get Emerald Glasss.
  1. Cadmium and sulphur Added to give Deep Yellow Colour.
  1. Thanium  Added to get Yellowish Green Glass.
  1. Gold Added with email concentration (.001%) provides Rioh Ruby coloured Glass.
  1. Uranimum added to get Flurorecant Yellow and Green Colour.
  1. Silver added in compound form or Silver Nitrate, Produces Orange Red Yellow Glass.

Chemical composition in term of % (percentage ) by weight of various common type of glass.


Type of glass



Soda lime



Borate Silicate.



60 %– 70%

70% - 81%


54% - 65%




2% – 7%





5% - 12%












12% - 18%

4%  - 8%


13% - 18%










7% - 12%








18% - 30%


Chemical Properties of Glass: -

The Glass is mostly chemically inert. The corrosion of glass in contact with atmosphere and aquous solution takes a very long period.

The change (Chemical) depends on the composition of the solution reacting to it.

  1. Glass is a good thermal conductor.
  2. Glass is an Electrically Insulating Material.It does not conduct electricity.
  3. When light falls on glass , partly it is reflected at the surface, partly it is absorbed and part of light is transmitted.
  4. Coloured glass transmits only selective wave length of the light spectrum.


Glass normally does not transmit Ulra Violet Radiations (of short wave length) .Glass transmit infrared Radiations (Long Wave Length) – This turns the glass hot on other side also.

Mechanical Properties Of Soda – Lime – Silica Float Glass

Module of Raptue ,Mean Mor (50% Probability of breakage).

6,000 pel (41 MPa) Annealed
12,000 pel (83 MPa) Heat strengthened
24,000 pel (165 MPa) Tempered

Design Stress for 0.8%
Probability of breakage

2,800 pel (19 MPa) Annealed
5,600 pel (39 MPa) Heat Strengthened
11,200 pel (77 MPa) Tempered

Module of Elasticity (Youngs)

10.4 X 106 pel  (72 GPa)

Module of Rigidly (3hear)

4.3 X 106 pel (30 GPa)

Poieean’s Ratio


Bulk Module

6.2 X 10n pel (43 GPa)


156 lb/Fo (2530 kg/ Mn)

Coefficient of Thermal Stress

50 pel /FO (0.62 MPa /OC) 

Thermal Conductivity of 76 FO

6.5 Btu.In/hr. OF. (0.937 W.m/m2 .C2)

Specific heat at 76FO

0.21 btu/lbnF (0.66Kl/Kg.C)

Coefficient of linear Expansion (75 – 575F)

4.6 X 104 in /in Fo (8.3 X 10-4 mm/mm .OC)

Hardness (Moh’s Scale)


Saffening Point (ASIM C336)

1319OF   (716OC)_

Annealing Point (ASIM C336)

1018OF   (548OC)

Strain Point (ASIM C336)

952OF   (511OC)


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