Friday, August 28, 2020


Glass is a hard, transparent and brittle material with nature of super cooled liquid. On glass formation process it is cooled to below its melting point and then solidifies. Glass on windows after long time becomes slightly thicker at bottom part as glass molecules move down very slowly under gravity. Main raw material of glass is silica(SiO2). And the main source of silica is sand. Let’s discuss about some types of glass here.

1.  Silica Glass: Silica is heated to 1600oC to melt it and cooled down to form silica glass. It is used to make laboratory apparatus and electrical appliances.

2. Water Glass: Water glass is formed by heating silica with Sodium Carbonate or Potassium Carbonate at 800oC.  It is called water glass as it is slightly soluble in water. This glass is used to make silica garden.

3. Ordinary Glass: This glass is formed by heating 50% Silica, 15% Sodium Carbonate, 10% Calcium Carbonate and 25% old glass pieces at temperature of about 850oC. Bottles, windows glass and many other general purpose glass is made from this glass. This glass is also called soft glass and soda lime glass.

4. Hard Glass or Soda Lime Glass: This glass is prepared by heating potassium Carbonate and Calcium Carbonate with silica. It has high melting point and used to make hard glass test tube and othe laboratory apparatus.

5. Borosilicate Glass or Pyrex Glass: It is formed by heating sodium carbonate, calcium carbonate and boric oxide with silica. This is used to make heat resistive lab apparatus

6. Lead crystal Glass: This glass is formed by heating potassium carbonate and lead monoxide with silica. Mostly it is used to make lenses, spectacle glass etc as it has high refractive index.

To make coloured glass we have add some metal oxide on heating process.


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