We know that glass is used for making many articles, but we cannot use same type of glass for making everything. This means that we need different types of glass for different purposes. These types of glass can be made by changing the chemical composition of ordinary glass.
Now we will study different types of glass, their chemical composition and there uses.
1. Soda Glass or Soft Glass or Ordinary Glass
Soda glass is the cheapest and most commonly used glass. It is made by fusing a mixture of sodium carbonate, calcium carbonate and silica. It is called soda glass because it is prepared from soda ash or sodium carbonate. It is called soft glass because it becomes soft after heating.
Uses:- Soda glass is used for making glass tumblers, mirrors, window panes, electric bulbs, bottles, and dishes etc.
2. Potash Glass or Hard Glass
It is prepared by fusing a mixture of potassium carbonate, calcium carbonate and silica. As its name indicates it is very hard and have high melting point. It is also more resistant to action of acids.
Uses:- Hard glass is used for making hard glass laboratory apparatus.
3. Optical Glass
It is prepared by fusing potassium carbonate, lead oxide and silica.
Uses:- It is used for making lenses which are used in spectacles, cameras, microscopes, telescopes and other optical instruments. It is also used for making glass prisms.
4. Pyrex Glass or Borosilicate Glass
It is made by fusing a mixture of sodium carbonate, potassium carbonate, calcium carbonate, silica, borax and aluminium oxide.
Uses:- It is used for making laboratory apparatus such as flasks, and beakers because it can withstand high temperature while heating without breaking. It is also used for making ampoules which are used for storing the medicines for injections. In our homes the utensils which are used in microwave ovens are made up of Pyrex glass.
5. Safety Glass
It is prepared by sandwiching a thin sheet of plastic between two layers of glass by applying suitable adhesive on both the sides. These three layers are then joined together by the action of pressure and heat to form a single sheet of safety glass. This glass is very strong. It cannot be broken into small pieces by hitting with heavy objects. That is why it is called safety glass.
Uses:- It is used mainly for making the windscreens of automobiles, trains and aeroplanes. It is also used for making bullet-proof jackets.
6. Photo Chromatic Glass
This glass has a unique property of becoming dark coloured when exposed to bright sunlight and coming back to original state when bright sunlight is removed. This happens due to the presence of a layer of silver bromide over it.
Uses:- This glass is used for making spectacles, cameras and goggles.
7. Lead Crystal Glass
It is made by fusing a mixture of potassium carbonate, lead oxide and silica.
Uses:- This glass has the property of shining so it is used for making expensive glass products.
8. Coloured Glass
Coloured glass is made by mixing small amount of colouring materials such as certain metal oxides during the preparation of glass. For example
| S No. | Name of the metal oxide | Colour imparted to the glass |
| 1. | Iron oxide | Brown |
| 2. | Cobalt oxide | Blue |
| 3. | Copper oxide | Red |
Glass Fibers
Glass fibers are fibers which are used in various applications in industries. These are obtained by forcing molten glass through very fine holes under high pressure. It is used in two forms:
1. Glass wool
Glass wool is a mass of loose glass fibers. Glass wool is an excellent insulator that is why it is used as an insulation material in refrigerators, electric ovens etc. Glass wool is also used for making fire proofing clothing.
2. Optical Fibers
The optical fibers are thin and long glass fibers which transmit signals in the form of light through the process of total internal reflection. These days’ optical fibers are being used extensively in examining the internal parts of human body by a technique called as ‘endoscopy’. These also help in conducting surgical operations. Optical fibers are also being used in telecommunication like telephones.
Test your understanding and answer these questions:
- What are different types of glass? Explain.
- What is soda glass? give its use.
- What is potash glass? give its use.
- What is pyrex glass? give its use.
- What is optical glass? give its use.