What is glass? What are different types of glass?

What is glass? What are different types of glass?

 

Invention of glass is considered to be an accident when some nomadic tribes ignited fire on sandy patches of ground and in the ash that was formed they found a shiny and transparent material. They thought it to be a magic. First formal creation of glass is considered to have occurred way back in about 2500 B.C.E. in the Middle Eastern countries where sand is found in abundance.

Today, glass is widely used in our daily lives and finds numerous applications. Sir Alastair Pilkington is credited with industrial manufacturing of glass through mass production. The main ingredients of glass are Limestone, Soda Ash and Sand.

Limestone, sand and soda ash are mixed and poured into a tank furnace that looks like a small swimming pool. These materials are heated to 1500 to 1700 degrees Celsius. The furnace is shallow at one end and deep at the other. The raw material moves slowly towards the deeper end with gravity. Silica melts at a very high temperature. In order to lower its melting point, soda ash is added. Limestone makes glass insoluble in water. The heated mixture melts and forms a jelly-like substance that we call molten glass. The molten substance is then formed into different shapes as it cools down and solidifies. Addition of some metallic oxides gives colour to the glass – red, blue, green, yellow etc.

We use glass for different purposes. There are nine types of glass - Soda glass or soda-lime glass, Coloured glass, Plate glass, Safety glass, Laminated glass, Optical glass, Pyrex glass, Photo-chromatic glass and Lead crystal glass.
 
Soda Glass: It is the most common variety of glass. It is used for making windowpanes, tableware, bottles and bulbs.
 
Coloured Glass: Coloured glass is much in demand. It is used for decorating walls, making sunglasses, and for making light signals for automobiles, trains and airplanes.
 
Plate Glass: It is used in shop windows and doors. Plate glass is thicker than ordinary glass.
 
Safety Glass: It can also be called shatterproof glass. It is made by placing a sheet of plastic such as celluloid between sheets of glass. It is used in automobiles and bulletproof screens.
 
Laminated Glass: It can also be called bulletproof glass. Several layers of safety glass are bound together with a transparent adhesive. It is used in air planes and windshields of cars.
 
Optical Glass: It is softer than any other glass. It is clear and transparent. Potassium and lead silicates are used in making optical glass. It is also called flint glass. The main use of flint glass is in the manufacture of lenses, prisms and other optical instruments.
 
Pyrex Glass: In Pyrex glass boron oxide is used. Boron oxide expands very little when heated, thus, Pyrex glass does not crack on strong heating. It has a high melting point and is resistant to many chemicals. Laboratory equipment and ovenware are made of this glass.
 
Photo-Chromatic Glass: Photo-chromatic glass turns dark in shade when exposed to bright light and returns to its original lighter shade in dim light. This happens because of silver iodide that is added to this glass during manufacturing. Silver iodide becomes dark with the intensity of light.
 
Lead Crystal Glass: This type of glass has a high refractive index, and so sparkles and is used for high quality art objects and for expensive glassware. It is also called cut glass because the surface of the glass objects is often cut into decorative patterns to reflect light. Cutting of the glass adds additional refraction to the surface of the glass. To achieve higher refractive index lead oxide is added during the process of manufacturing.
 
(Reference: http://www.preservearticles.com/201012291928/glass-types.html)
 
 
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