Glass is a transparent amorphous kind of solid, which may be hard or brittle and is used in windows, some types of bottles and spectacles or eyeglasses. In technical words we can say that glass is an inorganic substance which is cooled to rigid state without its crystallization. Silica is the main component of the glass.
Types of glass:
Glasses are divided into its different types based on the composition and use of the glass. Different types of glasses have their different chemical and physical properties. Following are certain kind of glasses according to these properties:
1. Commercial Glass also called Soda-lime glass
2. Borosilicate Glass
3. Glass Fibre
Types of special glass include:
1. Vitreous silica
2. Alkali-barium silicate glass
3. Optical glass
4. Aluminosilicate glass
5. Glass Ceramics
6. Technical Glass
7. Sealing glass
Recycling of glass:
Glass recycling means converting waste glass into a usable form (product) like bottles etc. In fact glass recycling is an important part of the hierarchy of waste management- Reduce, Reuse and Recycle. Glass recycling has many advantages like conservation of raw materials, reduction in energy consumption and the reduction in the amount of glass waste thrown to dumps. Glass recycling is done by crushing glass materials in to the basic form of the glass which is called cullet and then mixing it with some other raw materials like silica sand or limestone.
There are certain steps in the process of the recycling of glass:
1. First step starts from the consumer’s side. People are encouraged to throw glass containers to the selected bins from where they are picked up by the recycling factory vehicles. If the bottle is returnable and can be reused then it is more advantageous to reuse that bottle rather than recycling it because it saves energy, time and money.
2. Glass is selected according to its composition. Glasses with impurities are discarded because these kinds of glasses can not be used for recycling purpose.
3. Glass recyclers then must clean the glass. Caps and labels are removed from the glass bottles. Bottles with caps and labels can not be used for recycling purpose because these caps etc can cause damage to glass manufacturing machines or the glass manufactured after including these caps and labels has a very low quality and customers does not buy this kind of low quality glass.
4. In the last step all glass materials are crushed in to the basic form of the glass Cullet. Cullet is then mixed with the silica sand. Limestone or soda ash for the manufacturing of more glass substances to save more glass recycling cycles.
5. Most of the glass we see in our daily life is commercial kind of glass like glass used in jars, windows, bottles or glasses for drinking purpose. Sand is the main component of commercial glass. Sodium bicarbonate (Na2CO3) is also used which lowers the temperature of fusion (the temperature at which fusion occurs). It lowers the fusion temperature to 800 oC which is actually 1700 oC in case of the sand only.