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:
“Only one marriage I regret. I remember after I got that marriage license I went across from the license bureau to a bar for a drink. The bartender said, “What will you have, sir?” And I said, “A glass of hemlock.””
—Ernest Hemingway (1899–1961)
“O, what a noble mind is here o’erthrown!
The courtier’s, soldier’s, scholar’s,eye, tongue, sword,
Th’ expectancy and rose of the fair state,
The glass of fashion and the mold of form,
Th’ observed of all observers, quite, quite down!”
—William Shakespeare (1564–1616)
“A sudden violent jolt of it has been known to stop the victim’s watch, snap his suspenders and crack his glass eye right across.”
—Irvin S. Cobb (1876–1944)