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• Some Special Kinds of Glass and Their Properties and Uses
• Colored glass

Glass is a hard, brittle substance that is usually transparent or translucent. It is made by melting together sand (silicon dioxide), soda (sodium carbonate), limestone (calcium carbonate), and other ingredients. The simplest form of glass (containing only sand, soda, and lime) is known today as plate or window glass.

Scholars believe that the first humans to make glass may have been Phoenician sailors living around 5000 B.C. Examples of glass used for

weapons, ornaments, and money from Egypt and Mesopotamia—dating to about 1550 B.C.—still survive.

Humans may well have learned about glass-making by witnessing the natural formation of glass by lightning bolts. When lightning strikes areas where sand, soda, and limestone...