# Glass - liquid or solid?
**URL:** https://boards.straightdope.com/t/glass-liquid-or-solid/135210
**Category:** Cecil's Columns/Staff Reports
**Created:** [November 4, 2002, 1:53pm UTC](https://boards.straightdope.com/t/glass-liquid-or-solid/135210 "2002-11-04T13:53:20Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@braintree](https://boards.straightdope.com/u/braintree)
#### Post date: [November 4, 2002, 1:53pm UTC](https://boards.straightdope.com/t/glass-liquid-or-solid/135210/1 "2002-11-04T13:53:20Z")
I’d always thought that nearly all substances could be gas liquid or solid depending on their temperature. For example, carbon dioxide is a gas at room temperature but you can buy dry ice which is frozen CO2. Water is a gas as steam, liquid at room temerature and a solid as ice. So howcum we have to ask if glass is a liquid or a solid? My theory: if you can break it it’s a solid, if it gets you wet it’s a liquid and if you can inhale it then it’s a gas. So why the distinction for glass, eh?
---
### Author:  [@AndrewL](https://boards.straightdope.com/u/AndrewL)
#### Post date: [November 4, 2002, 1:58pm UTC](https://boards.straightdope.com/t/glass-liquid-or-solid/135210/2 "2002-11-04T13:58:17Z")
Glass is an amorphous solid and does not flow. It can deform under its own weight, but so will any other solid. Cecil is wrong on this one.
---
### Author:  [@jjimm](https://boards.straightdope.com/u/jjimm)
#### Post date: [November 4, 2002, 2:00pm UTC](https://boards.straightdope.com/t/glass-liquid-or-solid/135210/3 "2002-11-04T14:00:03Z")
Mercury doesn’t get you wet, but it’s a liquid.
---
### Author:  [@AndrewL](https://boards.straightdope.com/u/AndrewL)
#### Post date: [November 4, 2002, 2:27pm UTC](https://boards.straightdope.com/t/glass-liquid-or-solid/135210/4 "2002-11-04T14:27:27Z")
From:
[http://www.urbanlegends.com/science/glass.flow/glass\_flow\_math.html](http://www.urbanlegends.com/science/glass.flow/glass_flow_math.html)
"Therefore, we can not apply a yield stress to the glass that could cause it to flow without first breaking our sample. "
"This applies to glasses below 600C (or 270C for infinite time lengths). "
---
### Author:  [@mnemosyne](https://boards.straightdope.com/u/mnemosyne)
#### Post date: [November 4, 2002, 2:40pm UTC](https://boards.straightdope.com/t/glass-liquid-or-solid/135210/5 "2002-11-04T14:40:53Z")
Also, though, there are many divisions and definitions of “gas, liquid, solid”. The you start getting into weird stuff like amporphous solids, and supercritical fluids (liquid and gas-like properties at the same time) and then a whole bunch of definitions fall apart. Even something as simple as water - it has (at least) SIX different forms of ice, all with different lattices and conditions under which they are formed. It just isn’t as clear-cut as you say.
---
### Author:  [@jmacleod9975](https://boards.straightdope.com/u/jmacleod9975)
#### Post date: [November 4, 2002, 3:00pm UTC](https://boards.straightdope.com/t/glass-liquid-or-solid/135210/6 "2002-11-04T15:00:47Z")
Dear Cecil,
Your answer and the following discussion about seeing through glass
completely misses the point of why we can see through glass and not
other materials. It has nothing to do with being a solid or a liquid.
For instance you can see through diamonds and they are solids. And you
cannot see through mercury which is liquid a room temperatures. Also
you can see through ice if it is air bubble free, which is a solid and a
crystal.
The truth of the matter is that the reason we can see though certain
materials is that the energies that the material absorb do not match
with photons with frequencies between about 400-700 nanometers. This
happens to be the frequency that our eyes are sensitive to. Remember
light is just a small part of the electromagnetic spectrum. If we were
only sensitive to ultraviolet light instead of “normal” we would not
see through glass at all.
Thanks.
Jared
---
### Author:  [@Phlosphr](https://boards.straightdope.com/u/Phlosphr)
#### Post date: [November 4, 2002, 3:04pm UTC](https://boards.straightdope.com/t/glass-liquid-or-solid/135210/7 "2002-11-04T15:04:42Z")
Apparently our Lord of Lords has never been to New England, or even in a house older than say 200 years. I live in a house built by a man - and his family - in the good year 1756. Some of the glass windows in the house are original and still intact, yet one can not discern what is beyond them because they have _Warped_ out of shape over the years. Also anyone who lives in a very old house knows never to run their finger over the top of a pane of glass, because the top is razor sharp because over the years the glass has _melted_ or _flowed_ downwards, give the appearance of strations in the glass and making the bottom thicker than the top.
So, the quote from our lord of lords from the Discovery Magazine guy is also a load of shit, because the windows in my house are certainly not millions of years old and they _have_ deformed and changed shape, maybe the bottom is roughly 5% bigger than the top. Perhaps!
\*\*Don’t hurt me sir.
---
### Author:  [@porkchop\_d\_clown](https://boards.straightdope.com/u/porkchop_d_clown)
#### Post date: [November 4, 2002, 3:29pm UTC](https://boards.straightdope.com/t/glass-liquid-or-solid/135210/8 "2002-11-04T15:29:29Z")
The reason colonial windows are thicker at the bottom is because, guess what, they were made that way.
The technique of making pane glass was imperfect and led to uneven thicknesses. The glaziers thought (rightly, I believe) that putting the thicker end down would leave a stronger window.
---
### Author:  [@porkchop\_d\_clown](https://boards.straightdope.com/u/porkchop_d_clown)
#### Post date: [November 4, 2002, 3:31pm UTC](https://boards.straightdope.com/t/glass-liquid-or-solid/135210/9 "2002-11-04T15:31:00Z")
The simple proof that the legend about colonial windows is wrong is this: Many European cathedrals have windows older than anything in the USA. Not one has a puddle of glass at the bottom of the window frame.
---
### Author:  [@whitetho](https://boards.straightdope.com/u/whitetho)
#### Post date: [November 4, 2002, 5:51pm UTC](https://boards.straightdope.com/t/glass-liquid-or-solid/135210/10 "2002-11-04T17:51:28Z")
You don’t tug on Superman’s cape, you don’t spit into the wind, and when you comment on a Cecil column the powers-that-be want you to include a link to same: [How come you can see through glass?](http://www.straightdope.com/classics/a1_120.html). (This column also appears on page 120 of the original _Straight Dope_ collection.)
---
### Author:  [@Coda](https://boards.straightdope.com/u/Coda)
#### Post date: [November 4, 2002, 5:54pm UTC](https://boards.straightdope.com/t/glass-liquid-or-solid/135210/11 "2002-11-04T17:54:22Z")
\*\* porkchop\*\* - If that acertion is correct, then why do older windows have the striations in them ? I too live in an older home, early 19th century. And some of the windows in the barn and in the upper floors have the striations phlosphr is talking about. Why would they be made that way and not clear. I understand their method was imperfect, but are you telling me they could not make clear glass, that is to say, glass without striations in it?
---
### Author:  [@happyboy](https://boards.straightdope.com/u/happyboy)
#### Post date: [November 4, 2002, 9:14pm UTC](https://boards.straightdope.com/t/glass-liquid-or-solid/135210/12 "2002-11-04T21:14:59Z")
I was under the impression that the reason we “knew” glass was a slow-moving liquid was research done on European cathedral windows. Each color of a stained glass pane is cut to fit a certain shape; the randomly “heavy” end couldn’t always be placed “at the bottom.” I’m sure I read this in one of the scientific magazines a few years ago: Discover, National Geographic, etc.
Also, it seems to me that if glass were simply a solid that deforms under its own weight (instead of flowing), the old windows would be thicker at the bottom without becoming thinner at the top. There’s no reason for the heavy top to compress inward unless some of it is flowing to the bottom. Just a thought.
---
### Author:  [@Scylla](https://boards.straightdope.com/u/Scylla)
#### Post date: [November 4, 2002, 10:29pm UTC](https://boards.straightdope.com/t/glass-liquid-or-solid/135210/13 "2002-11-04T22:29:18Z")
Cecil’s wrong on this. The calculations that are used to show glass flowing over millions or billions of years (the calculation I have shows a plate of glass 1 meter tall and one centimeter thick, would deform by only 10 angstrom units in 10 billion years,) are somewhat fanciful, as they are not applicable to the actual physical properties of glass **which does not flow** , the exercise is purely theoretical, as the stochastic ooze of matter itself is greater than this.
If we want to talk about something’s flow rate, what we are really talking about is viscosity. All elements in either solid or liquid form have a viscosity, which is measured in units called poises.
Glass is less viscous and more solid than most conventional solids. Even glasses like germanium oxide (the softest most viscous glass) are held tightly together by strong chemical bonds, and it does not flow whatsever. This can be demonstrated by its anelasticity.
For example, if you twist a length of lead, not quite to its breaking point, leave the pressure on for a while and then release it, the lead will permanently have retained the shape you have twisted it into.
If you try this with glass the glass will return to its original shape slowly. This occurs because a length of glass is basically like one giant molecule in that it is chemical bonds which hold it into its shape, and those chemical bonds are not permanently malleable without destroying the glass or heating it up past it’s glass transition temperature.
To give you an idea of what I’m talking about, metallic lead and gold have a viscosity in poises of about 10 to the 11th power (water is .01.)
Glass at room temperature has a viscosity between 10 to the 20th and 10 to the 32nd power in poises, more I believe than all metals (but I’m not looking up any more poise values.)
Nobody here believes that a solid metal flows or isn’t a solid, so if we are going to argue that glass isn’t a solid were going to have a tough time saying what a solid is, because there are few if any things that are better as an example of a solid than solid glass.
If glass could flow consider that lead has a flow rate about a billion times higher than glass.
The myth about flowing glass is persistent, but the fact is that glass has a viscosity rate lower than that at which flow can exist.
It is this way because Stochastic ooze is the inherent quality of matter to screw around and move about on the quantum level. Stochastic ooze is greater than glass’s poise value.
Glass in infinitely anelastic.
Sorry to burst your bubble, Cece, but I got you again.
---
### Author:  [@Arnold\_Winkelried](https://boards.straightdope.com/u/Arnold_Winkelried)
#### Post date: [November 5, 2002, 2:00am UTC](https://boards.straightdope.com/t/glass-liquid-or-solid/135210/14 "2002-11-05T02:00:42Z")
From [Scientific American’s website](http://www.sciam.com/askexpert_question.cfm?articleID=000E7305-705E-1C71-9EB7809EC588F2D7&catID=3):
> [@](#):
>
> Window glass at room temperature has a nearly incalculable relaxation time, approaching the age of the universe itself. For all practical observations, this glass is a solid. But its solidity is in the eye of the beholder.
I think that the SciAm “expert” falls into the camp “glass is a liquid that flows very very slowly, so you may as well call it a solid.”
---
### Author:  [@AskNott](https://boards.straightdope.com/u/AskNott)
#### Post date: [November 5, 2002, 3:35am UTC](https://boards.straightdope.com/t/glass-liquid-or-solid/135210/15 "2002-11-05T03:35:46Z")
I have neither the credentials nor the nomex gloves to touch solid vs. liquid.
HOWEVER, we’re dancing around the key, here. How was glass made in those crude days when panes were allegedly thicker on one side? Why was this quality present in early American Colonial glass, when European glass makers had got past that problem long before? Were they using birchbark and deerskin molds?
–Nott (I nearly typed Noot)
---
### Author:  [@Scylla](https://boards.straightdope.com/u/Scylla)
#### Post date: [November 5, 2002, 4:26am UTC](https://boards.straightdope.com/t/glass-liquid-or-solid/135210/16 "2002-11-05T04:26:18Z")
> [@](#):
>
> I think that the SciAm “expert” falls into the camp “glass is a liquid that flows very very slowly, so you may as well call it a solid.”
In that case, the term “solid” is meaningless. Most metals fall into that category. Are gold and lead liquids at room temperature?
The flow rate of glass is a total bullshit excuse to call glass a liquid. Some jerkwad scientist got started calling it a liquid a long time ago (I can look up the name,) simply because it doesn’t form a crystalline structure, and probably because he saw that 12th century stained glass was thicker at the bottom than at the top, and he said “Oh, that’s a liquid,” and he told everybody and everybody believed him and started calling it a liquid, and they’ve been trying to defend it ever since.
It’s rigid, inelastic, forms strong chemical bonds, and if you cut into a shape put it on a table, and wait out entropy watching it, and waiting for it to flow, it has a better chance of spontaneously teleporting through the table, and falling on the floor and breaking than it does of actually flowing at all.
The random tendency of subatomic particles to move relative to each other inherent to all matter (stochastic ooze) is greater than the flow rate of glass which means the stupid thing will have evaporated into nothingness long before it flows **at all**.
What this means is that matter in general has a higher flow rate than glass. It is inherently more solid than the matter of which it is compromised!
Carl Sagan in his book **The Demon-Haunted World** (or something it’s still in a box since I moved,) calculates that the permeability of matter is such that if you park your car on a slanted floor next to a wall, and the parking brake fails, your vehicle is statistically likely to flow through the wall in about 32 billion years because of the spaces between subatomic particles.
Are you going to tell me that Bucks are permeable? That they’re gases? That they’re not solid?
I’ll put it another way:
Say you go out to your dealership and you buy the new H2 which gets something like 10 to the negative 50,000 miles to the gallon.
It’s a nonsense number, because at that level of gas mileage, the distance you can travel on a gallon of gas is smaller than a planck space which is the fundamentally smallest unit of space that exists. Nothing below the distance of a planck space actually exists. It’s the fundamental unit of space.
Since a gallon of gas isn’t enough to move your H2 one fundamental building block of distance, your mileage would be exactly zero.
This is exact same thing that happens with the flow rate of glass. In the real world it’s flow rate is less than the fundamental building blocks of the universe itself!
It’s flow rate is entirely hypothetical.
In my earlier post I talk about a pane of glass a meter high by a centimeter thick thickening by 10 angstroms at the bottom in 10 billion years. Do you think that’s a real number? There are vast spaces (relatively speaking) between the subatomic particles that compromise the matter of which glass is itself made. In that much time they will move relative to each other more than that.
Glasses flow rate is a nonzero number, but so is the flow rate of everything else.
Glass doesn’t flow. It never has flowed, it never will flow. It will stay exactly in the same shape until the fundamental matter of which it is made up evaporates or some stupid kid comes along and drops it.
If we’re talking in terms of flow rates and flow rates define whether something is a solid or a liquid, than glass is a solid if most anything else is.
But even the scientists got tired of trying to figure out how to call glass a liquid since liquids flow and glass doesn’t in any real sense, and gave up. They just wanted to keep calling it a liquid because of its structure. Now finally they’ve caved and admitted that they’ve been screwing the pooch for a few hundred years, and decided to come clean and say that glass is an “amorphous solid,” and you want to argue that it’s still a liquid?
Do you also still believe that when it thunders that’s God bowling?
Get with the program man.
Glass is a solid.
Try this simple experiment:
Throw a baseball at a window. When it hits the window does it break, or does it splash? What the hell do you think all those broken pieces are all over the place… ripples?
Now if you walk up to the guy whose window you broke and tell him you’re not going to pay for it, because it wasn’t really a solid and was going to turn into a puddle in 30 or 40 billion years anyway you will deserve the punch in the mouth such overeducated, underinformed opinions have coming.
Still not convinced?
Go find me an example of rounding or flowing in a broken piece of volcanic glass a couple of billion years old.
---
### Author:  [@Scylla](https://boards.straightdope.com/u/Scylla)
#### Post date: [November 5, 2002, 4:38am UTC](https://boards.straightdope.com/t/glass-liquid-or-solid/135210/17 "2002-11-05T04:38:18Z")
> [@](#):
>
> \*Originally posted by AskNott \*
> \*\*I have neither the credentials nor the nomex gloves to touch solid vs. liquid.
> HOWEVER, we’re dancing around the key, here. How was glass made in those crude days when panes were allegedly thicker on one side? Why was this quality present in early American Colonial glass, when European glass makers had got past that problem long before? Were they using birchbark and deerskin molds?
>
> –Nott (I nearly typed Noot) \*\*
What they would do is blow a bubble of glass just like a soap bubble. Then they’d spin it as fast as they could. It would stretch out along the axis of the spin and flatten at the front and back due to centrifugal force. This same process would make it thinner at the center of the axis and thicker at the end.
Picture the way they make a pizza by spinning it in the air. It’s thicker at the edges than at the middle where it gets stretched out, right?
Same thing.
Nowadays they make glass pretty much perfectly flat by pouring a thin layer on top of another molten liquid with a lower solidification temperature. When the glass cools, they just lift it off the molten liquid, and voila, it’s flat.
---
### Author:  [@Kalt](https://boards.straightdope.com/u/Kalt)
#### Post date: [November 5, 2002, 4:49am UTC](https://boards.straightdope.com/t/glass-liquid-or-solid/135210/18 "2002-11-05T04:49:40Z")
i thought it was pretty well established that the “glass is really a liquid” factoid was in fact an urban legend. For every old window that had glass heavier at the bottom there is another equally old window that has glass heavier at the top (from the way they originally put the window in).
---
### Author:  [@psychonaut](https://boards.straightdope.com/u/psychonaut)
#### Post date: [November 5, 2002, 6:53am UTC](https://boards.straightdope.com/t/glass-liquid-or-solid/135210/19 "2002-11-05T06:53:42Z")
Perhaps what is needed to settle this matter is an experiment such as the following:
[http://www.physics.uq.edu.au/pitchdrop/pitchdrop.shtml](http://www.physics.uq.edu.au/pitchdrop/pitchdrop.shtml)
In this experiment, a container (actually, a funnel with the bottom plugged) was filled with liquid pitch in 1927. (Pitch is a substance which, like glass, is a solid at room temperature, and is also quite breakable – you can shatter it with a hammer.) It was allowed to cool, solidify, and settle over a period of several years. Then the bottom of the funnel was cut, allowing the pitch to start flowing. The drops fall at a rate of about once every ten years.
The site referenced says that the viscosity of pitch is over a billion times that of water. If the viscosity of glass is in that neighbourhood, then an experiment such as this might be feasible.
---
### Author:  [@Scylla](https://boards.straightdope.com/u/Scylla)
#### Post date: [November 5, 2002, 2:15pm UTC](https://boards.straightdope.com/t/glass-liquid-or-solid/135210/20 "2002-11-05T14:15:44Z")
> [@](#):
>
> The site referenced says that the viscosity of pitch is over a billion times that of water. If the viscosity of glass is in that neighbourhood, then an experiment such as this might be feasible.
That would be like saying a dust speck and a galaxy are about the same size.
[Next page](https://boards.straightdope.com/t/glass-liquid-or-solid/135210.md?page=2)