Glass is made by melting silica, a chemical that comes from sand. At extremely high temperatures, silica melts and becomes liquid. Other substances are usually added to the melted silica to make the glass strong. In its liquid state, glass can be molded into different shapes.
Glass was first made at least 4,000 years ago. About 2,000 years ago, people in the Middle East discovered that molten (melted) glass could be blown into different shapes. They put a gob of glass on the end of a metal tube. Then they blew air through the tube. The glass at the end of the tube expanded, just like a balloon. Glass blowing remained the usual method for making glass vessels until the early 1900s. In 1903, an automatic glass blowing machine was invented.
Glass can also be made into sheets that are flat and smooth. It can be shaped in molds. Substances can be added to glass to give it color. And once glass is cold, it can be decorated by cutting and painting.
Glass can be recycled. It is sorted by color and then melted in big furnaces. The molten glass is formed into new shapes.
Modern glass is made by melting together several minerals at very high temperatures. Silica in the form of sand is the main ingredient and this is combined with soda ash and limestone and melted in a furnace at temperatures of 1700°C. Other materials can be added to produce different colors or properties.
The basic ingredients of glass have remained unchanged for thousands of years. Silica sand, lime and soda still make about 90 percent of the world's glass, but the production scale has been considerably increased to meet modern demands.
Today's glassmakers scrupulously select tons of pure raw materials, weigh them to the ounce, thoroughly mix them and then feed the mixture, or batch, to gigantic tank furnaces that can hold more than 1,000 tons of molten glass. Although added cullet, or scrap glass of the same formula to be manufactured, speeds the melting process, the furnace must be heated to about 2,800 degrees Fahrenheit! So corrosive is molten glass at this temperature that the process has been compared to melting a block of ice in a container of sugar. The heat-resistant furnace walls must usually be replaced every two to four years.
However, once the process is in operation it continues day and night, week after week, until repairs or changes in formula force a shutdown. The batch is continuously fed into one end of the furnace while workable glass, mixed and refined to uniform viscosity, free of bubbles and impurities, is drawn from the other. The red-hot liquid is then ready to be drawn, pressed or blown into service.
The basic ingredients of glass have remained unchanged for thousands of years. Silica sand, lime and soda still make about 90 percent of the world's glass, but the production scale has been considerably increased to meet modern demands. Today's glassmakers scrupulously select tons of pure raw materials, weigh them to the ounce, thoroughly mix them and then feed the mixture, or batch, to gigantic tank furnaces that can hold more than 1,000 tons of molten glass. Although added cullet, or scrap glass of the same formula to be manufactured, speeds the melting process, the furnace must be heated to about 2,800 degrees Fahrenheit! So corrosive is molten glass at this temperature that the process has been compared to melting a block of ice in a container of sugar. The heat-resistant furnace walls must usually be replaced every two to four years. However, once the process is in operation it continues day and night, week after week, until repairs or changes in formula force a shutdown. The batch is continuously fed into one end of the furnace while workable glass, mixed and refined to uniform viscosity, free of bubbles and impurities, is drawn from the other. The red-hot liquid is then ready to be drawn, pressed or blown into service.
Glass basically is a mixture of sand, flint, spar or various other silicon substances, with one or the other of the fixed alkalies, and occasionally with a metallic oxide. The metallic oxide generally used is litharge, or some other material made from lead.
Glass is a consistent material of uncertain phase, and is created when the viscous molten material cools very quickly to below its glass transition temperature, lacking adequate time for a regular crystal lattice to be created. Glass is a biologically motionless matter which can be created into smooth and impermeable surfaces.
Glass is usually prepared in factories with the help of furnaces, and every section of common glass comprises of 70 to 72 per cent of silicon dioxide by weight and the chief raw material used to create glass is sand.
Glass has been made by human about 4500 years ago.it is made from a fusion of silicia in the form of sand ,potassium or soda, lime, and occasionally some other chemicals as well.They are melted at high temperature together and cooled at air temperature ,when they get cooled down and the material gets hard , it has a smooth flowing shape like a liquid.thus the glass is formed.
Glass is basically made by melting silica (SiO2). To make processing easier by lowering the melting point of silica, sodium carbonate is often added. Thus silica melts at 1500oC after adding sodium carbonate. Further, oxides of Calcium, Magnesium and Aluminum are added to increase the durability of the glass and prevent its solubility in water (a feature that comes about as a result of adding sodium carbonate). This type of glass may be known as soda lime glass. Contemporary science has also made it possible for us to produce glass without silica, for example flouroaluminate glass and chalcogenide glass. Fiber optics is a widespread use example of silica free glass.
