Glass has evolved into an inevitable material that is being used in an average person’s day to day life. The transparency nature of the glass has given it a unique purpose oriented material. The manufacturing process of glass has gone through remarkable progress since its inception.
The earlier found natural glasses were used during the Stone Age period for making tools. The sharp nature of the glass edges made it to be used as the cutting tools. During the Bronze Age, the Soda ash and sodium bicarbonate were used to form the glass material. This was extensively found at Egypt and since then glass manufacturing process has got upgraded each time resulting in a better quality of glass. It became one of the luxury materials as years passed. Its scope widened and as a result of which it gradually became indispensable in a household.
Two different types of glass manufacturing are the Float-glass process and glassblowing process. The Float-glass process yields a Sheath of glass material while the glassblowing process produces glass for containers. In the case of the float-glass process, the molten glass material is processed on the bed of molten metal. This was majorly used for the windows and other such needs. The glassblowing process was done by exploiting the inflation nature of the glass material. The molten glass was blown into the desired shape by introducing air in the molten glass material. As this blob starts to lose heat, it gets hardened.
The three major steps involved in the glass production are the Batchhouse, Hot end and Cold end. The Batchhouse involves the handling of the required raw materials. The selection of raw materials that forms the very initial step in the glass manufacturing is made by considering various factors that governs the nature of the glass and temperature plays a vital role. The raw materials are mixed in the required proportion and if needed some of them are also pre-heated. This is then transferred through the conveyor belt to the furnace. The main raw material used in the process of glass making is the fused silica. The fused silica requires a very high glass transition temperature which might not be easy to achieve. And so Soda is added to this mixture of silica which will help in reducing the glass transition temperature. This will make the entire mixture water soluble and yield unwanted effects. To avoid this, lime, Magnesium oxide and aluminum oxide are added. This ultimate mixture produces a glass material that is of high durability.
This is followed by the hot end section of glass production. The prepared raw materials are poured into the furnace that is capable of molting the glass at a very high temperature of 1575°c. It’s the composition and nature of the end glass product result and the construction of the furnace that decides the transition or the heating temperature. The furnace is supported by natural gas or the oil. The other process that is a part of the hot end section is the forming process. In this process, the molten glass material is shaped into the desired container or sheath form. It is of two types and they are as follows: the blow and blow process, the press and blow method which differs based on the shape of the end glass container type. For getting a narrow neck bottle done, the blow and blow process is adopted. In this method, the molten glass material is
poured in a baffle and blown into the desired shape by making use of a valve and a ring mould. The Initial level of this includes providing the details for the glass mould and thus forming a molten glass material with a detailed shaping but is slightly lesser than the actual size. This is known as the parison, which is finally blown into the final product with the help of the final moulds. The molten glass that has been cut into cylindrical shapes is used for this purpose. Shape of the glass product depends upon the mould’s shape and these products come in various shapes and sizes. The air cooling mechanism is used to cool the soft hot glass for taking out the container. This is done allowed to anneal. Annealing is done with the help of a machine to bring about even hardening of the glass container. It is done by heating the finished glass container for about 500°.
The process of Internal Treatment is done following the forming process for the containers that are used for liquids that might chemically react with the glass container. In this process, the sulphur or the fluorine gas mixture is introduced at very high temperature. This will render a restriction for the glass container to react with the liquid filled.
Next section of glass production is the Cold end which includes the testing of the glass products that are manufactured. During this process, the completely finished product is tested for any defect and then finally labeled for shipment.
Most common defects that one can find in the glass products are the uneven surfaces or the small cracks that would have been formed during the production process. Sometimes, there are chances for the brick lining of the furnace to get mixed with the molten glass, which might result in the presence of refractory stones in the glass containers. The bubbles that are formed in the end glass product are known as blisters and it spoils both the quality and the credibility of the glass material that has been manufactured. Inspecting the Product before shipping forms the very crucial aspect of glass manufacturing as this process helps in establishing the quality and standard of the end products. Both manual inspection and machine based inspection are done by the glass manufacturing companies. Machines are used in the case of a large scale production. It speeds up the entire process and also increases the possibility to inspect almost all the glass products that have been manufactured. The inspection of the products helps to determine the source of defect. And, by detecting the defect’s source, the future damage for the glass products can be avoided.
After the process of inspection, the processed glass material is labeled as per the company’s standards. The glass products undergo two coatings during its production. One is at the end of the hot end process and the other at the initial stage of the cold end process. The coating that is done in the hot end process renders adhesiveness for the coating that will be available at the cold end process for the glass material. The second coating is done during the initial stages of the Cold end process to make the glass product resistant towards scratches and the few other external factors.Commonly, Tin oxide is used as the first coating and the Polyethylene wax forms the second coating for the glass product. The coatings are required to render a standard quality for the glass product. It finally leads to the packaging process that almost all the glass manufacturing company’s take care of due to the brittle nature of the glass products. Transportation of the packaged product forms a very important factor to avoid the damages that might get induced in the glass products. Glass products have the added advantage of getting recycled easily. This makes it to be considered as one of the stable materials that can be used extensively.
The Float-glass process which is also known as Pilkington process involves the production of glass sheets. A metal sheath that has high melting point is used as the base for floating the molten glass during the glass production. The basic raw materials required for the float-glass production are the sand, sodium carbonate, dolomite, sodium sulfate and limestone. Window panels and the glass panels that are found in various electronic appliances are few examples that would illustrate the Float-glass products.
There are other types of glasses which differ in terms of the raw materials being used and process that are followed. The ones that do not make use of silica as one of the raw material is known as the network glass and this type of glass material is used in the fiber optics. The other forms of glass materials are the Electrolytes, Amorphous metals, Aqueous solutions, Molecular liquids, Polymers, colloidal glasses and ceramic glasses.
Recycling these glass materials has developed as a major process due to its extensive use by the ever growing large population. The need for the glass products have been rising ever since it was manufactured. And the ease that exists in the recycling glass products increases its use by a large volume.