The idea that glass after being formed is in a state of flux concerns the belief, held by many, that because glass is a "super cooled liquid" it actually has a degree of "flow" at temperatures within the human comfort range. This urban legend would have us believe that the windows in colonial homes and in very old stained glass windows are thicker at the bottom than at the top because glass is a "supercooled liquid" and is slowly flowing. Ahh that pesky gravity. The acceptance of that story is not based on fact but on a mythological story that has been circulating for many many years. (I read it on the internet so it must be true). There was a time, in the dim dark past that, in my ignorance I believed in the myth of glass flow. Without question I accepted the myth of glass flow. My blind acceptance of what I thought passed for fact should not be a trait of the curious mind. What could I have been thinking when I accepted the "fact" that the Rose Window would soon spill out of the confines of the lead cames that have held it in place all these years. Okay, lets get to the heart of the myth of glass flow, but before reading on do some research and look up the word "poise" and then when you understand what poise is then look up the poise of lead and glass. If you're still a believer in glass flow after that then Read On!



I was made aware of the fallacy of the glass flows myth many years ago by the late great glass chemist, Nick Labino. Nick offered this simple analogy, "...if the windows found in early Colonial American homes were thicker at the bottom than the top because of "flow" then the glass found in Egyptian Tombs should be a puddle." Wow, that was a shocker. And there's this one from Wikipedia, "If glass flows at a rate that allows changes to be seen with the naked eye after centuries, then the effect should be noticeable in antique telescopes.

Any slight deformation in the antique telescopic lenses would lead to a dramatic decrease in optical performance, a phenomenon that is not observed". I just love real world examples! For those of you that are still skeptical I cite research that tells us that although 1/2 of the glass in old stained glass windows is thicker at the bottom, take three guesses where the other half are thicker and the first two guesses don't count. You got it, sides and top. Hmmm, what do you suppose that indicates? In other words, if glass flowed then ALL the glass in antique windows would be thicker at the bottom and research tells us that's not true. If you still don't believe it, read below what the brainiacs have to say. When that know - it - all antique dealer whips out the urban legend of glass flow, send him or her to this page. After they read all the information below and they still refuse to believe that glass doesn't flow have them email me with a reason other than "thicker at the bottom."



Finally, Dr. Neumann relates the following. Read this carefully: "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."

What Dr. Neuman and Labino is saying is that if glass flowed, all the glass that comprised antique windows should be thicker at the bottom, but we know that is just not true.

Authors note: In the real world glass is for all intents and purposes (in every practical sense) frozen in place but in the laboratory physicists are still at work proving that there is some movement as purported in this abstract sent to me by Dan Watts. The abstract is a real page turner.