Making Glass From Sand
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Brief History of Glass
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History doesn't show when people first began to manufacture glass or even who discovered how to turn sand into glass. What we do know is that the oldest pieces of manufactured glass are beads that date to around 3500 BC. Glass was primarily used as jewelry until the 16th century BC when artisans discovered how to fashion glass into vases and other art objects. The first written manual containing instructions on how to make and shape glass dates to 650 BC. Glass was so precious and hard to come by that glass objects were used as currency by ancient Romans, Egyptians and Greeks.
Facts About Glass
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When sand is heated to 1700 degrees Celsius it melts. The molecular structure of sand changes during the heating and subsequent cooling and becomes glass. Glass is actually a cross between a solid and liquid, with the crystalline structure of a solid and the molecular structure of a liquid, and is known as an amorphous solid. This is why old window glass appears wavy, the glass slowly "drips" or slides down the pane, leaving the top of the window pane thinner than the bottom of the window pane. Glass is prized for being chemically inert and tolerant of high temperatures, which makes it ideal for use in laboratories and kitchens. Glass can also be recycled over and over without damaging its molecular structure. In fact, much of the glass made now is made from recycled glass.
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How Glass Is Made Today
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In most commercial glass factories sand, recycled glass, sodium carbonate and calcium carbonate are heated together to make glass. The sodium carbonate lowers the temperature at which sand liquefies and the sodium carbonate makes the glass sturdier. Glass made from this mixture is referred to as soda-lime-silica glass, and most manufactured glass is made from this. However, other chemicals and dyes can be added to make "specialty" glass. Blue dye added to liquid soda-lime-silica glass makes blue-colored glass. Pyrex makes its glass containers by adding the chemical boron oxide. Glass is shaped into an end product by pouring liquid glass into molds or floating it on molten tin and allowing it to cool. Artisans still shape glass by "blowing" it. A hollow pipe is dipped into liquid glass, as the artisan blows through the pipe the glass expands like a balloon. The artisan can then shape the glass by twirling the pipe and controlling how much air he uses.
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Comments
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"This is why old window glass appears wavy, the glass slowly "drips" or slides down the pane, leaving the top of the window pane thinner than the bottom of the window pane." This is a falsehood. Old panes are thicker at the bottom due to casting processes, or so I have read repeatedly by archaeologists.
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"the glass slowly "drips" or slides down the pane, leaving the top of the window pane thinner than the bottom of the window pane." This is a myth, the glass is thinker at the bottom because it was placed there that way. Medieval methods of glass production were imperfect and resulted in glass of nonuniform thickness. Glass does not flow or drip.
