Glass is technically an amorphous solid, not a liquid, and old windows are thicker at the bottom due to manufacturing methods, not because glass flows over time.
Sources
- https://sciencenotes.org/is-glass-a-liquid/ (sciencenotes.org)
- https://www.scienceabc.com/pure-sciences/is-glass-solid-or-liquid-does-glass-flow-amorphous-crystalline-melting-windows-cathedral (scienceabc.com)
- https://www.scientificamerican.com/article/fact-fiction-glass-liquid/ (scientificamerican.com)
- https://ceramics.org/ceramic-tech-today/glass-viscosity-calculations-definitively-debunk-the-myth-of-observable-flow-in-medieval-windows/ (ceramics.org)
- https://www.newportrestoration.org/glass-is-not-a-liquid-early-windows-glassmaking/ (newportrestoration.org)
- https://www.glassnotes.com/WindowPanes.html (glassnotes.com)
- https://math.ucr.edu/home/baez/physics/General/Glass/glass.html (math.ucr.edu)
- https://www.britannica.com/technology/crown-glass (britannica.com)
- https://historicengland.org.uk/whats-new/research/back-issues/the-origins-and-use-of-medieval-glazing-in-england/ (historicengland.org.uk)