Glass is made from sand that is melted into a liquid form. The sand must be heated to 3090 degrees Fahrenheit to melt. When the liquefied sand cools, the structure changes, and it does not turn back into grains of sand. Instead, the liquid sand can be formed and cooled into glass, says Explain That Stuff.
In a commercial glass manufacturing plant, glass is made from sand, recycled glass, soda ash and limestone that are all heated together to make the liquid version of glass. From there, the liquid version of glass is formed into glasses, bottles, windows or other glass pieces.
Different types of glass are made by adding additional products to the glass mixture. Iron and chromium chemicals are added to the glass mixtures to make green tinted glass, boron oxide is added to glass to make Pyrex, and bullet-proof glass is made from multiple layers of glass and plastic mixed together.
Scientists call glass an "amorphous solid" because it is a solid material without a regular crystalline structure. Some refer to glass as a "frozen super-cooled liquid," says Explain That Stuff.
Glass naturally occurs as volcanic glass, also known as obsidian. The first glass was manufactured by man around 3500 B.C. in Easter Mesopotamia and Egypt, according to History of Glass.