Glass is an enigma to many people. Most of us know that it is made from sand, but how can tiny grains of rock be turned into a transparent, durable material? Glass is actually made using liquid sand. To turn sand into a liquid, it needs to be heated at a temperature of 1700°C (that’s 17 times the boiling point of water)! Once the sand has been turned into a molten liquid, it completely changes its structure and can never quite set into a solid form again. Instead it becomes a sort of frozen liquid (referred to as an amorphous solid). Once the sand is liquefied, it can be mixed with various other ingredients to create the glass we are used to seeing everyday.
Modern glass manufacturers use a mixture of sand, cullet (recycled glass material), calcium carbonate (limestone) and sodium carbonate (soda ash) to create new glass items. The soda ash reduces the melting point for sand, therefore saving energy, but in turn this also makes the glass able to dissolve in water, which isn’t ideal! The limestone is added to stop this from happening. This mix is commonly referred to as soda-lime-silica glass.
How Are Glass Bottles Made And Moulded?
Once you have the base ingredient for your glass bottles ready to go, all that remains to be done is to mould it into shape. This is mostly done by pouring the glass mix into the designated mould and left to cool and set. Up until the point of setting, the glass mixture must be kept at the same temperature throughout the process, as even a small increase or decrease could affect the structure of the glass.
This same process is used to make any type of mass produced glass item, but you can also create beautifully shaped glass using the old technique of glass blowing. This is a specialist job that is highly skilled and is mainly used to create stunning, unique glass figurines and one-of-a-kind glassware pieces. This is done by wrapping a lump of molten glass (known as a gob) around an open pipe, which is slowly rotated whilst air is blown through it, which causes the glass to blow up like a balloon. You can create all types of different shapes using this method, depending on how the glass is rotated or blown!