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This is not the case; glass is a [[solid]. |
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<h3>Does glass flow?</h3>
It is sometimes claimed that glass may show some of the properties of [[liquid]]s that [[rheology|flow]] at room temperature, albeit very slowly. As an example, it is sometimes claimed that old windows are often thicker at the bottom than at the top, and that this might be due to flow.
This is not the case; glass is a [[solid]. It is a bit unclear where this belief came from, or if there was ever any evidence to support it. One possible source of this belief is that when panes of glass were commonly made by glassblowers, the technique that was used was to spin molten glass so as to create a round, mostly flat and even plate (the Crown glass process, described above). This plate was then cut to fit a window. The pieces were not, however, absolutely flat; the edges of the disk would be thicker due to [[centrifugal force]]s. When actually installed in a window frame, the glass would be placed thicker side down for the sake of stability. There is anecdotal evidence that occasionally such glass has been found thinner side down, as would be caused by carelessness at the time of installation.
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