what is glass

Glass is a non-crystalline solid that is often transparent, brittle, and chemically inert. It has widespread practical, technological, and decorative use in window panes, tableware, and optics, among other things. Glass is most often formed by rapid cooling (quenching) of the molten form; some glasses such as volcanic glass are naturally occurring. The most familiar and historically the oldest types of manufactured glass are "silicate glasses" based on the chemical compound silica (silicon dioxide, or quartz), the primary constituent of sand. Soda-lime glass, containing around 70% silica, accounts for around 90% of manufactured glass. Glass is made from natural and abundant raw materials such as sand, soda ash, and limestone that are melted at very high temperatures to form a new material. At high temperatures, glass is structurally similar to liquids, but at ambient temperature, it behaves like solids. As a result, glass can be poured, blown, pressed, and molded into plenty of shapes. Glass manufacturing has an age-old tradition that dates back to around 3500 BC when glass is believed to have been first artificially produced in Egypt and Mesopotamia to be used as jewelry and later as vessels. Since then, processes have constantly evolved from craftsmanship to todays high-tech industrial processes, and the number of glass types and applications has multiplied.