Glass is an amorphous (non-crystalline) solid material. Glasses are typically brittle and optically transparent.
The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica (SiO2) plus sodium oxide Na2O from soda ash, lime CaO, and several minor additives. Often, the term glass is used in a restricted sense to refer to this specific use.
In science, however, the term glass is usually defined in a much wider sense, including every solid that possesses a non-crystalline (i.e., amorphous) structure and that exhibits a glass transition when heated towards the liquid state. In this wider sense, glasses can be made of quite different classes of materials: metallic alloys, ionic melts, aqueous solutions, molecular liquids, and polymers. For many applications (bottles, eyewear) polymer glasses (acrylic glass, polycarbonate, polyethylene terephthalate) are a lighter alternative to traditional silica glasses.
Read more about Glass: Silicate Glass, Structure, Glass Versus Supercooled Liquid, Glass Art
Famous quotes containing the word glass:
“Before the beginning of years
There came to the making of man
Time, with a gift of tears;
Grief, with a glass that ran;”
—A.C. (Algernon Charles)
“Thou didst create the night, but I made the lamp.
Thou didst create clay, but I made the cup.
Thou didst create the deserts, mountains and forests,
I produced the orchards, gardens and groves.
It is I who made the glass out of stone,
And it is I who turn a poison into an antidote.”
—Muhammad, Sir Iqbal (1873–1938)
“Heaven has a Sea of Glass on which angels go sliding every afternoon. There are many golden streets, but the principal thoroughfares are Amen Street and Hallelujah Avenue, which intersect in front of the Throne. These streets play tunes when walked on, and all shoes have songs in them.”
—For the State of Florida, U.S. public relief program (1935-1943)