Is glass a liquid?

Glass is not a liquid. While it has some properties that are not common in solids, it is still not really a liquid. People only really consider it a liquid if their definition of a solid is a very viscous liquid.

In other words, people saying its a liquid are just arguing semantics. The fact of the matter is that glass really doesn't have the properties of liquids that would allow it to be defined as such. Specifically, glass does not deform or flow under its own weight.

Hmm Moonrise I heard some differing viewpoints on that. I remember in high school, that they *might* have said that glass is a slow slow moving liquid. My teacher said to look at windows that are 50+ years old that they are thicker at the bottom than they are at the top. I could be wrong however, it was quite a long time ago.

Moonrise -  1189 pts -  (2 years ago)

Those are inaccurate. There are glasses from Roman times that have shown no difference in thickness at the bottom than the top. Same thing with stained glass in old cathedrals. Any "sagging" seen is due to the manufacturing process. Another example is telescope lenses that are over 150 years old. ANY deformation or sagging in these would make the lenses completely useless, yet they work just as well now as they did when they were made.

Glasses are amorphous solids. There is a fundamental structural divide between amorphous solids (including glasses) and crystalline solids. Structurally, glasses are similar to liquids, but that doesn't mean they are liquid. It is possible that the "glass is a liquid" urban legend originated with a misreading of a German treatise on glass thermodynamics.

	Moonrise -  1189 pts -  (2 years ago)
	Hm, I've never heard that explanation (the German misreading). It certainly adds some insight as to where people got the idea.

The reason why people say "look at old windows" is because people back then couldn't cut glass accurately. My Chemistry professor from college gave a long explanation about why glass is a solid and NOT a liquid. People who believe that glass is a liquid are just easily fooled by unique ideas.