Question

The raw materials used in glass manufacturing are soda, limestone and __________

Answer 1

Hint: To answer this question, you must recall the preparation of glass and its constituents. While soda and limestone are main raw materials involved in the formation of glass, another raw material needs to be added to increase the fusibility of glass.

Complete step by step answer:
Glass is manufactured using abundant natural raw materials. The raw materials used in the manufacture of glass are $71\% $ silica (sand), $14\% $ soda ash (sodium carbonate), $11\% $ limestone (calcium) and $4\% $ other ingredients. To this mixture a very important component is added which is known as cullet.
Cullet is waste glass or broken pieces of glass, either scrap or from the manufacturing process, or from recycling centres or kerbside collection systems. It increases the fusibility of glass and prevents the loss of alkali by volatilization during the reaction in forming of new glass. Cullet also reduces the cost by saving energy and raw materials.

Additional information:
Once the raw materials and cullet are mixed together, the mixture is melted in furnaces continuously, heated to a temperature of around ${3180^o}F$. The raw materials entering the furnace take around 24 hours to be converted into glass.
Next, the molten glass is flown through a series of distribution channels,which are known as forehearths, to forming machines. At the end of the forehearths, the glass flow is cut into lumps of molten glass (gobs)whose weight, shape and temperature are controlled precisely.
The forming machines transform the compact mass of the gobs into the desired shape. Then, the finished glass object is taken out the finish mold, held briefly over a cooling plate and is conveyed away. The glass is still at temperatures of over ${1000^o}F$ when they come out of the forming machines.

Note:
Use of cullet glass in manufacturing of new glass is useful and environment friendly as well because it cuts costs, makes fusing of glass easier and promotes recycling of non-biodegradable waste products.