GLASS MANUFACTURING

How are glass bottles made?

To make glass bottles, moulds are used. A lump of molten glass is dropped into the mould. A rush of compressed air forces the molten glass to reach the bottom of the mould. Due to the pressure of the compressed air, the glass sticks to the sides of the mould and acquires it's shape. This is then transferred to another mould where it is given the final shape of the bottle or any other special shape desired.

Float Glass

Float Glass is used in windows, glass doors, table tops etc. Making glass for windows is a tough task. The glass has to be absolutely smooth and clear without any distortions. One way of making this glass to flatten it between rollers , however the sheet so formed is not perfect. A better way to manufacture perfect glass is by the float glass method. Raw materials used in the manufacture of glass such as Sand, Waste Glass and Calcium Carbonate is introduced into the furnace. The temperature in the furnace is around 1400 degrees centigrade. Due to this high temperature the raw materials melt and combine to form molten glass. This molten glass is made to float on a stream of moving molten metal, such as tin. The molten metal is very smooth and hence the glass floating on this molten metal also becomes very smooth. The molten metal is kept in an atmosphere free from oxygen in order to prevent the formation of metal oxide which could cause the glass to be uneven in shape. The glass is carried forward by rollers which take it through different temperature zones so that cooling is achieved.

Changing the properties of Glass

The properties of glass such as its color can be changed by adding chemicals. for example red colored glass can be obtained by adding selenium sulfide, blue glass can be obtained by adding copper oxide and milky glass can be obtained by adding alumina or phosphate. Green tint in the glass can be removed by adding cobalt and selenium oxide.