Glass and Its Uses
It is needless to point out the use of glass in modern times especially in the manufacture of many useful house-hold and novelty articles.
But the discovery of glass itself is accidental. It is said that many centuries ago, a party of sailors were lighting a fire on the shore. The heat melted the sand and small stones on which the fire was built resulting in the formation of glass.
Glass therefore is made of sand and other minerals. When a tougher variety is required, a little aluminum Is added.
The glass is melted and a blower takes up some, on the end of a large pipe and blows it into whatever shape it is required. Bottles and flasks are made in this way. When molten glass is allowed to run between rollers, It comes out as a sheet. After cooling, it is polished and made fit for use.
Opaque glass is one through which one cannot see. After the making of the glass, fine sand is blown against the glass with great force and this gives it the frosted appearance which makes it opaque. This is called mirror.
We are now making unbreakable glasses. This is very valuable and useful for motor cars and the windscreens cannot be broken due to accidents and there is no danger for the passengers being cut by the flying pieces of glass.
The glass which is used for the manufacture of spectacles, telescope and microscopic lenses and other scientific instruments naturally requires more care in its manufacture than ordinary glass.
First of all the glass is mouldod roughly to the shape required. Then it is cut with diamond to the exact shape. A diamond is always used because a diamond is so hard hat it can cut glass quite easily. After this, the glass is polished first with rough polishing material then with fine materials. The finer type of work is all done by hand and requires great skill on the part of the workers.
Nowadays, plastic glass is often used particularly in aircraft and optical work. The great advantage of plastic glass is that it is both light in weight and unbreakable.
We find beautiful windows of stained glass. In these glass colour is not painted on the glasses but actually mixed into it along with the sand used for the manufacture of glass. A stained glass windows therefore consists of many pieces of glass of different colours fitted together like a jig-saw puzzle to form a picture. The various pieces of glasses are joined together by pieces of lead. As lead is a heavy metal,stained glass windows are very heavy and they are very costly.
Venetians were famous glass blowers and we still find many examples of their glassware in important cities all over the world.
