fact of the day from the future (Japan time):

glass gradually degrades when in contact with air, the speed at which this happens (which is pretty slow regardless) depends on the formula used in the batch. Lots of older glasswork suffers from pretty dramatic degradation, and in museums sometimes you can notice a fine white dust on the base of the display. This can be observed even in modern glass batches (which are more consistent and more resilient generally), especially when the glass is first removed from the annealer, or if it breaks. When it's first removed from the annealer, it will make a squeaky noise when rubbed against another piece of glass, this is because the surface is still rough (although not observably so), it will stop making the noise shortly. Freshly broken glass has a microscopically sharp edge, which quickly degrades, becomes ever so slightly blunt.

Glass would still be considered a solid at that temperature, although you are sort of right, it's amorphous, meaning it lacks the strong structure of crystalline solid and such. So theoretically given thousands of years (maybe more), you would be able to observe such a change. It would be dependent on the structure of the glass, and the ambient temperature/amount of heat it absorbs on average. Amorphous solids all have a deformation temperature (forget the proper name), as well as a melting point. For glass, this is around 900 F, so not reachable in daily circumstances, so it probably wouldn't deform from heat (also, fire = shattered windows, not melted). But if the bonds between the molecules aren't ideal (angle, etc.) it would be possible for them to shift. It's definitely over-exaggerated though, so I'd say no, it is definitely not a liquid, and no, you can't just find an antique window and have it be thicker at the bottom. Although theoretically the molecules could end up shifting around some, it would take far too long to be measured by our eyes.


coincidentally, our annealers start at around 900 degrees F (plateau there for a little bit), and slowly bring the glass down to room temperature. and not in a strictly linear pattern. they stop at certain temperature plateaus to allow the stress to seep out of the glass so it is stronger when removed from the annealer. I think one of the peaks is around 400 F but I forget the rest.

Yea, I'm a student, I mainly do casting and furnace work. and no offense, but if you have, it's probably from the manufacturing process (it's very possible that older techniques could produce uneven float-glass, or that it wasn't cut or cold worked perfectly), seriously, look into amorphous solids & glass transition (the term for when an amorphous solid transitions into a slightly viscous phase). The idea doesn't mesh with the observed characteristics of the material. Any silica or soda-lime based glass won't deform significantly until it gets close to 1000 F. The only possible exception would be if the bonds were not at ideal angles, there's a relatively small range, if the bond isn't somewhere around a 140 degree angle, it very well could deform slightly. But that's a process that would take much much longer than heat deformation.

here's a good explanation of the myth, with citations from academic papers on the characteristics of glass, in case you're still not sure

I love klein bottles, so much. here's a slightly more practical one