Ever see windows in an old building? Notice how the glass appears wavy, distorted? That’s because glass, a liquid, has been running and settling over the years in the window frame.
are you sure it just not the process that they used to make the glass? I have never seen such a example in glass ware that is over 100-150 years old.
Urban legend!
This wavy glass was made before truly flat, float or rolled sheet glass became common. It was made from spun disks.
Old buildings (ones erected before the invention of flat glass) have windows made from spun glass - made by spinning a disc of molten glass and cutting bits from the cooled disc. Window glass from such a source could very well appear distorted, especially if you used an edge piece.
“Ever see windows in an old building? Notice how the glass appears wavy, distorted? That’s because glass, a liquid, has been running and settling over the years in the window frame.”
No, this is because the modern “tin float” method of making sheet glass is so superior to the older ways of doing it.
However, glass DOES very, very slightly flow over many decades. Telescope lenses and mirrors lose their figure over these time periods. It isn’t much, but telescope mirrors and lenses are figured to incredible accuracy in order to provide maximum focal sharpness, and even small errors become obvious.
Or they made crappy glass way back when. Did you see the pane when it was originally installed?