Quote:
Originally Posted by Bill Douglas
Even glass itself has liquid properties. Supposedly old windows have more glass at the bottom of the pane than at the top after being verticle for 80 to 100 years.
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"The question of antique windowpanes has been addressed by Plumb, 1989[2]. He noted the following:
[...W]hy are the panes of antique window glass thicker on the bottom than the top? There really are observable variations in thickness, although there seem to have been no statistical studies that document the frequency and magnitudes of such variations. This author believes that the correct explanation lies in the process by which window panes were manufactured at that time: the Crown glass process.
In other words, while some antique windowpanes are thicker at the bottom, there are no statistical studies to show that all or most antique windowpanes are thicker at the bottom than at the top. The variations in thickness of antique windowpanes has nothing to do with whether glass is a solid or a liquid; its cause lies in the glass manufacturing process employed at the time, which made the production of glass panes of constant thickness quite difficult."
"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."
"Structurally, glasses are similar to liquids", e.g., one doesn't actually "cut" glass with the age old, carbide wheeled glass cutter; one applies just enough pressure to scribe a line on the surface of the glass. That scribed line is a "break" in the "surface tension" of the "similar to liquid" glass.
When the pane of glass is then stressed on both sides of the scribed line (be it a straight or curved line), since the surface tension of the glass is broken by that scribed line, the glass parts along that weakened line.
Glass: Liquid or Solid -- Science vs. an Urban Legend
(Harrumph!)