Many old and historic homes have window panes that are thick and "wavery" at the bottom. Why?
Answer:
In spite of the persistent misconception, glass is an amorphous solid, not a liquid. The window panes are the same shape that they were when they were installed. At the time, the process of making window panes produced glass that was thin on one edge, and got thicker towards the other side. As it was installed, the panes were usually put in with the thick side down, to make them more stable.
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