Glass is really fascinating because it is strong enough to protect us, yet fragile enough to break so easily. It is made from the opaque sand yet it is transparent. We all know glass as a solid material, but in actual it is frozen liquid or amorphous solid. We cannot think of a world without the glass because it has that much important in today’s life.
The man has used glass for many centuries now. Historians have discovered that first use of the glass by men was Obsidian – a natural glass formed as a result of volcanic eruptions which melted the sand, which was used by men on the tip of the spear. Archaeologists have found the evidence of man-made glass in 4000 BC, but it was in 1500 BC, the production of hollow glass container started. In 1st century BC onwards it was made by blowing, but it was highly colored due to impurities contain in the raw material. But from the first century AD onwards colorless glass was made, if the color was needed, they would add the coloring agent.
Through the years glass manufacturing has gone many changes. Now it has become fully automated and can make a whole lot of glass within a short time.
The following steps are included in the manufacturing of glass:
- The raw materials like limestone, sand and soda ash are put in the tank furnace, which is very hot at a temperature of about 1500 degree Celsius. The tank is shallow at one end and deeper at the other end.
- The raw material will start to move slowly towards the deep end. Silica will melt only at a very high temperature in order to reduce the temperature soda ash is added, which will reduce the cost by saving the energy.
- The glass will become insoluble in water because of the presence of limestone.
- The raw material melts inside the furnace and a clear jelly like substance is formed, which can be used to get the desired shape and size of the glass.
The above mentioned steps show the general way of preparing the glass, but other raw materials are added as per the desired glass are required.
In general glass, manufacturing can be further subdivided into a Continuous and Batch process.
Continuous Process: In this process, raw materials are continuously added in the furnace from one end and the molten glass is removed from the other end. During this glass will passes through a different process in the furnace. It’s used for the preparation of high volume products like food and beverage containers, architectural glass etc.
Batch Process: All the raw materials are added at one time in the furnace and once it is melted, a portion of it removed and made into the desired product. This step is repeated until the vessel becomes empty of molten glass which ends one batch. This process helps to scale up or down the production as per the requirement. It’s mainly used for the small to medium scale production of aircraft lighting glass, custom molded glass for industry and signal application etc.
Nowadays we use glass in almost everything. We can find it in many different shapes, size, density etc., in short, we can find in different chemical and physical properties. Let’s look into the different type of glass.
Soda glass or soda-lime glass:
This is prepared by heating sodium carbonate and silica and it is the most commonly used variety. It’s used in window panes, tableware, bottle and bulbs.
Depending upon the color needed the desired metallic oxide are added to the hot molten mixture of sand, sodium carbonate and limestone to get the different color to the glass. It’s used for decorating walls, making sunglasses, for the making of light signals for automobiles, train and aeroplanes
It is made by floating a layer of molten glass over a layer of molten tin. It has got a smooth surface and is thicker than ordinary glass. This type used for the shop windows and doors.
This type of glass is also known as shatterproof glass and it is made by placing a sheet of plastic such as celluloid between a sheet of glass. It is used in automobiles.
In this type, several layers of safety glass are bound together with a transparent adhesive as the layer increase the strength of the glass will be more. It is also known as bulletproof glass.
It is used in the manufacturing of the lens, prism and other optical instruments. It is softer than other glasses and is clear, transparent. It is also known as flint glass. This optical glass is made by adding potassium and lead silicate.
It is highly resistant to heat because some of the silica is replaced by boron oxide, which expands very little on high heating, so it has a high melting point and resistant to many chemicals because of this it is used in the laboratory equipment and ovenware. It is also called as borosilicate glass.
In this glass, silver iodine is added so that the glass acquire the darker shade when exposing to brighter light and returns to original lighter shade in dim light.
Lead crystal glass:
This glass has a high refractive index with a maximum brilliance because the lead oxide is used to increase the refractive index, so has the maximum brilliance. It sparkles and its used for high-quality art object and expensive glassware. It is also called the Cut glasses because the surface is cut into decorative patterns to reflect light.
The glass is 100% recyclable and can be recycled infinite time without degrading its quality. So in order to save our environment from plastic pollution, we should pledge ourselves in using the glass products instead of plastic wherever possible.