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.
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 OHara (19261966)
“When youre thirsty and it seems that you could drink the entire oceanthats faith; when you start to drink and finish only a glass or twothats science.”
—Anton Pavlovich Chekhov (18601904)
“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 (18991961)