# Glass a Fluid? **URL:** \ **Category:** Factual Questions\ **Created:** [November 1, 2001, 9:44pm UTC](https://boards.straightdope.com/t/glass-a-fluid/90993 "2001-11-01T21:44:55Z")\ **Posts on this page:** 17\ **Page:** 1
**Author:** ![renigademaster](https://avatars.discourse-cdn.com/v4/letter/r/71c47a/32.png) [@renigademaster](https://boards.straightdope.com/u/renigademaster)\ **Post date:** [November 1, 2001, 9:44pm UTC](https://boards.straightdope.com/t/glass-a-fluid/90993/1 "2001-11-01T21:44:55Z")
My physics teacher was going on and on how glass is actually a superdense fluid that flows downwards and how they have proof from old buildings? Is this true? I read someware it wasn’t but can’t find the article. Thanks Ben ---
**Author:** ![Tranquilis](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tranquilis/32/3639_2.png) [@Tranquilis](https://boards.straightdope.com/u/Tranquilis)\ **Post date:** [November 1, 2001, 9:50pm UTC](https://boards.straightdope.com/t/glass-a-fluid/90993/2 "2001-11-01T21:50:24Z")
Ever look at a really old window? Did you notice that the glass was rippled? That’s not _entirely_ due to quality control issues. It’s also partly due to flow. ---
**Author:** ![Phlip](https://avatars.discourse-cdn.com/v4/letter/p/ed8c4c/32.png) [@Phlip](https://boards.straightdope.com/u/Phlip)\ **Post date:** [November 1, 2001, 9:52pm UTC](https://boards.straightdope.com/t/glass-a-fluid/90993/3 "2001-11-01T21:52:14Z")
It was presented to me as a plasma, not a fluid by my physics teachers. There are old churches in europe that have glass that is 2" thick on the bottom, and paper thin on the top because of downward flow. Ive seen photos in school, but no links unfortunately. ---
**Author:** ![45ACP](https://avatars.discourse-cdn.com/v4/letter/4/e5b9ba/32.png) [@45ACP](https://boards.straightdope.com/u/45ACP)\ **Post date:** [November 1, 2001, 9:54pm UTC](https://boards.straightdope.com/t/glass-a-fluid/90993/4 "2001-11-01T21:54:41Z")
Try this link [http://www.ualberta.ca/~bderksen/florin.html](http://www.ualberta.ca/~bderksen/florin.html) Conclusions from this person’s website? Glass is an amorphic solid, not a liquid. Old glass is variable in thickness due to the way in which it was manufactured. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [November 1, 2001, 9:59pm UTC](https://boards.straightdope.com/t/glass-a-fluid/90993/5 "2001-11-01T21:59:41Z")
[This link](http://www.howstuffworks.com/question404.htm) doesn’t 100% directly answer the OP but it implies that glass has many of the properties of a liquid. To summarize from the linked article most gasses and liquids are transparent. The reason for this is they have a much more loose and jumbled molecular makeup. This allows light ot pass through. As things turn into a solid they get a nice, tight knitting of the atoms that block light. The article mentions that solid glass is more like a liquid in its makeup of having a loose and jumbled makeup. While this doesn’t directly say glass is a liquid it seems to suggest they at least have a lot in common. ---
**Author:** ![BlackKnight](https://avatars.discourse-cdn.com/v4/letter/b/eb8c5e/32.png) [@BlackKnight](https://boards.straightdope.com/u/BlackKnight)\ **Post date:** [November 1, 2001, 10:00pm UTC](https://boards.straightdope.com/t/glass-a-fluid/90993/6 "2001-11-01T22:00:19Z")
This is all I could find in the archives at the Straight Dope, but I didn’t look very long and hard: [http://www.straightdope.com/columns/000211.html](http://www.straightdope.com/columns/000211.html) ---
**Author:** ![Gaspode](https://avatars.discourse-cdn.com/v4/letter/g/aeb1de/32.png) [@Gaspode](https://boards.straightdope.com/u/Gaspode)\ **Post date:** [November 1, 2001, 10:04pm UTC](https://boards.straightdope.com/t/glass-a-fluid/90993/7 "2001-11-01T22:04:17Z")
[The Master speaks.](http://www.straightdope.com/columns/000211.html) Both the rippling in old glass windows and especially the fact that old glass panes are thicker at the bottom than the top are mostly the result of the manufacturing process used. Back in the good old days glass was spun out on plates, letting centrifugal force produce the flat sheets. Needless to say this resulted in the edge being a different thickness to the center. Logically the glaziers placed the wider edge on the bottom. ---
**Author:** ![Cargogal](https://avatars.discourse-cdn.com/v4/letter/c/48db29/32.png) [@Cargogal](https://boards.straightdope.com/u/Cargogal)\ **Post date:** [November 1, 2001, 10:07pm UTC](https://boards.straightdope.com/t/glass-a-fluid/90993/8 "2001-11-01T22:07:10Z")
Glass is a supercooled liquid (think molasses taken to an extreme). Unlike solids, it does not have a crystalline molecular structure. It will flow and run, but takes a million or so years to do so (when they say supercooled, they mean it). The transition from liquid to solid is an exothermic transition; if you cool melted glass, it just cools, it does not turn into a solid. ---
**Author:** ![NutWrench](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nutwrench/32/20193_2.png) [@NutWrench](https://boards.straightdope.com/u/NutWrench)\ **Post date:** [November 1, 2001, 10:15pm UTC](https://boards.straightdope.com/t/glass-a-fluid/90993/9 "2001-11-01T22:15:31Z")
_\>Glass a fluid?_ Yes. But it flows so slowly, that for all practical purposes, it might as well be solid. It doesn’t have a crystalline structure that you might expect in what looks like a solid, rigid material. Like Gaspode pointed out, you can see these flow distortions in very old glass (cathedrals especially), where gravity has had several hundred years to act on the glass. Is IS weird, but consider that mercury is actually a _metal,_ which just happens to be a liquid in same temperature ranges that we humans like so much. 🙂 ---
**Author:** ![BlackKnight](https://avatars.discourse-cdn.com/v4/letter/b/eb8c5e/32.png) [@BlackKnight](https://boards.straightdope.com/u/BlackKnight)\ **Post date:** [November 1, 2001, 10:23pm UTC](https://boards.straightdope.com/t/glass-a-fluid/90993/10 "2001-11-01T22:23:46Z")
Here’s some more info: [http://www.urbanlegends.com/science/glass.flow/](http://www.urbanlegends.com/science/glass.flow/) ---
**Author:** ![Waverly](https://avatars.discourse-cdn.com/v4/letter/w/57b2e6/32.png) [@Waverly](https://boards.straightdope.com/u/Waverly)\ **Post date:** [November 1, 2001, 10:27pm UTC](https://boards.straightdope.com/t/glass-a-fluid/90993/11 "2001-11-01T22:27:57Z")
Glass is an amorphous solid, though if it helps, you can look at it as a super-cooled liquid. In the later case, the emphasis is on ‘super-cooled’, meaning that it has indeed solidified, but has done so too quickly for the material in question to form a crystalline structure. Glass does **not** flow. The ripples and the thicker bottoms of very old windows are indications of how it was [processed](http://www.abc.net.au/science/k2/moments/gmis9844.htm), not that it has been flowing all these years. Please let’s put this fallacy to rest. ---
**Author:** ![Bob\_Scene](https://avatars.discourse-cdn.com/v4/letter/b/e19adc/32.png) [@Bob\_Scene](https://boards.straightdope.com/u/Bob_Scene)\ **Post date:** [November 1, 2001, 10:37pm UTC](https://boards.straightdope.com/t/glass-a-fluid/90993/12 "2001-11-01T22:37:18Z")
> [@](#): > > \*Originally posted by Whack-a-Mole \* > **As things turn into a solid they get a nice, tight knitting of the atoms that block light.** It does indeed say that at [howstuffworks.com](http://howstuffworks.com), but it’s completely wrong. That page says the following: > [@](#): > > This progression from ordered to random organization is the primary reason that light can pass through liquids and gases. Just like bricks stacked neatly on top of one another, the ordered molecules of most solids are virtually impenetrable to light waves. That just isn’t true. The ordered structures of most pure, nonmetallic solids are, in fact, transparent. Salt crystals and a LOT of other kinds of crystals, for example, are transparent, despite having a very tightly ordered structure. And there are kinds of glass that are disordered like window glass, but aren’t transparent because they aren’t homogeneous. Opacity arises from either the presence of free electrons, as in a metal, or from scattering of light by different phases in substances of variable composition, like wood. The degree of order and bonding strength really aren’t relevant. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [November 1, 2001, 10:42pm UTC](https://boards.straightdope.com/t/glass-a-fluid/90993/13 "2001-11-01T22:42:23Z")
[Glass: Liquid or Solid – Science vs. an Urban Legend](http://www.ualberta.ca/~bderksen/florin.html) "Abstract I compiled this short article to address the widespread urban legend according to which glass is a liquid. It consists chiefly of a selection of quotes from recent works by specialists in materials science which state unambiguously that glasses are amorphous solids. I also speculate that at the origin of the legend may have been a misreading/mistranslation of an influential paper by Gustav Tamman. Additionally, I appended to the article an extract from an ASTM method of discriminating between a liquid and a solid. Contents Introduction An Urban Legend The Antique Windowpanes Story What the Scientists Say Origin of an Urban Legend? Conclusion Notes References Appendix " etc etc ---
**Author:** ![nth](https://avatars.discourse-cdn.com/v4/letter/n/58956e/32.png) [@nth](https://boards.straightdope.com/u/nth)\ **Post date:** [November 1, 2001, 10:48pm UTC](https://boards.straightdope.com/t/glass-a-fluid/90993/14 "2001-11-01T22:48:10Z")
glass is solid, but for arguments sake, let’s say it is liquid… if old cathedral glass has drip to the bottom, thus thicker at the bottom, won’t the color run, too? i have never seen these glasses in person, so can someone who have tell me. just wondering… ---
**Author:** ![45ACP](https://avatars.discourse-cdn.com/v4/letter/4/e5b9ba/32.png) [@45ACP](https://boards.straightdope.com/u/45ACP)\ **Post date:** [November 1, 2001, 10:49pm UTC](https://boards.straightdope.com/t/glass-a-fluid/90993/15 "2001-11-01T22:49:14Z")
Good link there, astro! Wish I had posted it further back up the list. 😉 (Glass is transparent and apparently I am invisible!) ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [November 1, 2001, 10:54pm UTC](https://boards.straightdope.com/t/glass-a-fluid/90993/16 "2001-11-01T22:54:54Z")
> [@](#): > > \*Originally posted by 45ACP \* > \*\*Good link there, astro! Wish I had posted it further back up the list. 😉 > > (Glass is transparent and apparently I am invisible!) \*\* Upon reflection I can see I inadvertently mirrored your link. I apologize, my error was transparent. ---
**Author:** ![Swede\_Hollow](https://avatars.discourse-cdn.com/v4/letter/s/3bc359/32.png) [@Swede\_Hollow](https://boards.straightdope.com/u/Swede_Hollow)\ **Post date:** [November 2, 2001, 2:17am UTC](https://boards.straightdope.com/t/glass-a-fluid/90993/17 "2001-11-02T02:17:22Z")
Here’s some more on the subject from Scientific American. As they conclude: “For all practical observations, this glass is a solid. But its solidity is in the eye of the beholder.” [http://www.sciam.com/askexpert/physics/physics12.html](http://www.sciam.com/askexpert/physics/physics12.html)