The Technology

History of Glass


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 Glass Anealing Ovennatural 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

IS-machineAuto Machine 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.

index1Most 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.

machine bThe 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.


The Technology

Although traditional glass-blowing and blow-molding methods are still used by artists and for custom applications, most bottle manufacturing is an automated process.  The development of glass bottle machining peaked with the advent of feed and flow machines, which enabled manufacturers to generate larger production runs than was previously possible. Glass production is broken down into two general categories: container production and sheet production. Bottle machining is part of glass container production.

Hot End Processes

Bottle manufacturing takes place at a glass container factory in multiple steps. The first stage of glass-container making begins with the hot end processes, which typically employ high amounts of heat to produce and shape a glass container. A furnace is first used to mold molten glass, which fed to the furnace as glass feed stock. Soda-lime glass stock accounts for the majority (around 90 percent) of glass products, and is typically largely comprised of silica, with about 10 percent each of calcium oxide and lime. Small amounts of aluminum oxide, ferric oxide, barium oxide, sulfur trioxide, and magnesia also account for about 5 percent of soda-lime glass. Before melting, cullet (recycled glass) is added to the stock, accounting for anywhere between 15 and 50 percent of the final glass composition.

Once the stock has been fed into the furnace, temperatures inside can be as high as 1675 degrees Fahrenheit. Next, one of two method forming methods is applied: press-and-blow or blow-and-blow.

    Press-and-blow formation takes place in an individual section (IS) machine and is the more commonly used method in glass-container production. IS machines have between five and 20 sections, all identical, which can each carry out the glass-container forming process simultaneously and completely. The result is that five to 20 containers can be produced with one machine at the same time.

When the molten glass reaches between 1050 and 1200 degrees Celsius it is said to be in its plastic stage, and it is during this phase that press-and-blow formation begins. A shearing blade is used to cut and shape the glass into a cylindrical shape, called a gob. The cut gob falls, and using gravitational force, rolls through the appropriate passage to reach the moulds. A metal plunger presses the gob into the blank mold, where it assumes the mould’s shape and is then termed a parison. Next, the parison is moved into a final mold, where it is blown into the mould to assume its final dimensions. This process is typically used for wide-mouthed glass containers, but can also be used to manufacture thin-necked bottles.

    Like press-and-blow formation, blow-and-blow takes place in an IS machine, where a gob is released during the plastic stage and moved along to the moulds. However, in blow-and-blow formation, the gob is forced into the blank mould using compressed air to push the gob into place. The gob, now a parison, is then flipped into a corresponding final mould where it is blown again, to form the interior side of the glass container. Glass bottles of varying neck thickness can be made using blow-and-blow formation.

After formation, bottles often undergo internal treatment, a process which makes the inside of the bottle more chemically-resistant, an important factor if the bottles are intended to hold alcohol or other degrading substances. Internal treatment can take place during formation or directly after, and typically involves treating the bottles with a gas mixture of fluorocarbon. Glass containers can also be treated externally, to strengthen the surface or reduce surface friction.


Once formation is complete, some bottles may suffer from stress as a result of unequal cooling rates. An annealing oven can be used to reheat and cool glass containers to rectify stress and make the bottle stronger. 

Cold End Processes

At this stage in glass production, the bottles or glass containers are inspected and packaged. Inspection is often done by a combination of automated and mechanical inspection, to ensure the integrity of the final product. Common faults include checks (cracks in the glass) and stones (pieces of the furnace that melt off and are subsequently worked into the final container), which are important to catch because they can compromise the component. Packaging methods will vary from factory to factory depending on the specific type of bottle and the size of the production run.