Glass is never solid.

[Toleman]

i heard that glass is not a solid and a pane of glass will be thicker at the bottem than to top after x amount of years. Is this true?

ta

[dundurn]

Yup - glass is a super-cooled liquid and will flow under gravity. Don't hold your breath waiting to see it though, it takes a while. If you prop a long piece of glass tubing in the corner of the science lab and forget to move it, it will develop a distinct curve over time.

[funkymoped]

no way !!!!
im impressed. i always thought glass was a solid.
i am confused though. glass being made from sand, how does it become a liquid ??? doesnt that change the laws of physics ?
:-)

[Teddio]

Glass is not a crystalline solid. Glass at room temperature does not flow under gravity. Below the Transition Temperature, a glass is a brittle solid and does not plastically deform.
The story that window glass slowly deforms under gravity is a myth.

[CT]

I agree with Teddio's answer. I'm sure it was in the news recently somewhere in a science article. They believe that the glass deformed in old windows etc when it was still cooling. ie when it was newly installed.

[wildwood]

No, it is not true.

It does become somewhat brittle and is harder to cut without breaking after 100+ years but never alters its shape.

[alfgbt]

Wish someone would tell my hammer glass is not solid.........

[dundurn]

Happy to be corrected. Sounds as though the bent tubing was the result of solid plasticity under (constant) stress rather than (fluid) flow.

The crown glass process will always produce glass of uneven thickness or with ripples etc. What I would find surprising is if mediaeval glass was always used with the thinnest portion uppermost. That may have been a convention but it's unlikely that no one ever made a mistake. So for all the examples of glass thicker at the bottom there should be some where it's thicker on one side or at the top.