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:
“Or your liquors seep to me, in this glass capsule,
Dulling and stilling.
But colourless. Colourless.”
—Sylvia Plath (1932–1963)
“Lay down, lay down the bigly bier,
Lat me the dead look on;
Wi’ cherry cheeks and ruby lips
She lay an’ smil’d on him.
O ae sheave o’ your bread, true-love,
An’ ae glass o’ your wine,
For I hae fasted for your sake
These fully day [is] nine.”
—Anna Gordon Brown (1747–1810)
“We are deranged, walking among the cops
Who sweep glass and are large and composed.”
—Karl Shapiro (b. 1913)