Years after grade school taught us about solids, liquids, and gasses, it is shocking to learn that one of the main revelations of that topic is not true: Glass is not a liquid.
Instead, glass is an amorphous solid. An amorphous solid is a non-crystalline solid, meaning that it “lacks the long-range order characteristic of a crystal.” This classification is shared with gels, thin films, and nanostructured materials. As an amorphous solid, glass is structurally similar to a liquid, but it is not factually a liquid.
The prolonged survival of this legend, chiefly among English speakers (and particularly among North Americans) is puzzling — especially when one considers that glass and glassy materials are readily available, and one can easily verify if one can pour a gallon of glass, or drain a pint of obsidian.
Many people cite antique windows as evidence that glass is a liquid. According to this logic, as time passes, the glass has slowly flown down so that it is thicker at the bottom. In actual fact, there has been no statistical research establishing that the bottom part of antique glass is thicker at the bottom to a statistically significant degree. The better explanation of the variation in glass thickness is attributed to the glass making process at that time.
The legacy of this urban legend, however, is still pervasive. Check Yahoo Answers and you will be inundated with misinformation. Let’s fix that!
Neumann, Florin. “Glass: Liquid or Solid — Science vs. an Urban Legend.” David W. Brooks Teaching and Research, 1996. Web. 14 July 2013.
Plumb, R. C. “Antique windowpanes and the flow of supercooled liquids.” Journal of Chemical Education, 1989. 66(12): 994-996.
A compilation of resources on the subject at Glass: Liquid or Solid — Science vs. an Urban Legend
Wikipedia distinguishes glass from its former designation as a “supercooled liquid” in its article on Glass