Hello all, I’m starting a intermittently regular series here on Dweebed: Debunkery. Where I’ll briefly (or sometimes not so briefly) debunk, examine, or otherwise explain the truth behind a common myth.
For the first entry into the Debunkery series we have liquid glass!
At some point in years past I heard that glass is actually a liquid that moves at an incredibly slow pace. That very old windows would have a thickening at the bottom glass when compared to the top. And that old windshields would eventually droop onto the steering wheel if left untouched. This is in fact untrue however.
Glass is for all regular Earthly purposes, a solid. That is to say at the temperatures and pressures that we encounter it at, it will remain solid and stable indefinitely. To the physicists or engineers out there however, glass is an “amorphous solid“, meaning it does not have a definite melting point. Some might call glass a “supercooled liquid” which is a term also applicable to igneous rocks and… well anything solid that can be liquid at higher temperatures.
Regarding the “thicker at the bottom” windows that one might come across; this phenomenon is caused by poorly made glass panes, or rather ones made with an outdated technique. These techniques included mainly variations on this theme; spinning the glass. As described in the link, molten glass was spun into large circles and then cut to make window panes. This often lead to a thicker side and a thinner side, not unlike spinning pizza dough. If spun too forcefully the outside rim would be thicker, if not spun forcefully enough, the inside. This resulted in panes that could be heavier on one end than the other, prompting them to be installed (although doubtedly 100% of the time) thicker side down.
So the next time to find a window with a thick bottom, look around for one with a thick top, chances are there’s one near by. And when you next hear that “glass is a liquid”, politely explain their misconception, and maybe even direct them here!
- Tipsy-Melting-Glasses: http://cdn.hiconsumption.com/wp-content/uploads/2013/01/Tipsy-Melting-Glasses.jpg