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:
“A glass of papaya juice
and back to work. My heart is in my
pocket, it is Poems by Pierre Reverdy.”
—Frank O’Hara (1926–1966)
“The highway presents an interesting study of American roadside advertising. There are signs that turn like windmills; startling signs that resemble crashed airplanes; signs with glass lettering which blaze forth at night when automobile headlight beams strike them; flashing neon signs; signs painted with professional touch; signs crudely lettered and misspelled.... They extol the virtues of ice creams, shoe creams, cold creams;...”
—For the State of Florida, U.S. public relief program (1935-1943)
“We all drew on the comfort which is given out by the major works of Mozart, which is as real and material as the warmth given up by a glass of brandy.”
—Rebecca West (1892–1983)