Is Glass Liquid Or Solid

By Anupum Pant

Glass stories have tormented me for years. A few well informed gentlemen, over the years, have communicated to me anecdotes that have contradicted and shown glass as liquid or solid, without solid proofs that could have helped me believe just one of them. A few days back, like I cleared my doubts about the gas station and cellphone story, I decided to find this out too. So, what is it really? Is glass liquid or solid?

Glass is a liquid?

1. Antique glass panes: A couple of years back I was told (I don’t remember where it came from) that glass windows of very old buildings have glass panes that have been found to be thicker at the bottom. That, according to them, absolutely proves that glass is a liquid that flows very slowly. And apparently explains, how the lower parts of these old panes get thicker – the glass from the upper part of the pane flows down as time passes. I thought it would be something like the world’s slowest experiment; so it could be true.

Till today, I had believed the same. It turns out, I was wrong all along.

Explanation: Firstly, there is no statistical study ever conducted that proves, all antique window panes are thicker at the bottom. Secondly, even if all of them are really thicker at the bottom, the difference in thickness has nothing to do with whether glass is a solid or a liquid. The cause of thicker bottoms is due to the fact that glass manufacturing process that was employed at the time wasn’t able to create perfect glass panes (with uniform thickness). The process made it almost impossible to produce glass panes of constant thickness.

Or, you could simply wait for a few years to see if perfect glass panes stuck on skyscrapers today mysteriously turn thicker in the bottom.

If you think you can NOT take my word for it, I have a quote for you from a distinguished science textbook – Glass Science – below:

Glass is an amorphous solid. A material is amorphous when it has no long-range order, that is, when there is no regularity in the arrangement of its molecular constituents on a scale larger than a few times the size of these groups. A solid is a rigid material; it does not flow when it is subjected to moderate forces. – Doremus, R. H. (1994)

2. Glass is a Super-cooled liquid? : This misunderstood phrase from Gustav Tammann’s book is probably the origin of the myth that glass is a liquid. The quote “glass is a frozen supercooled liquid” has been misquoted hundreds of times with the word “frozen”, forgotten. Today, this misquotation has grown to such great levels that it is actually difficult to go down and extricate the original quote that contained the word “frozen” in it. One word can indeed make a huge difference.

Finally, glasses are only amorphous solids. Where the term amorphous and solid have been separately been explained clearly in the year 1994 by Doremus R. H.
Together, these two words mean the same as definition of two separate words put together. Glass is not a liquid.

If you haven’t read about the ancient Nanotech marvel, Lycurgus cup, you are probably missing something amazing about ancient glass technology.

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