Talk:Glass/Archive 1

Glass Properties
I am desperately looking for glass properties and by properties I mean: Young's Modulus, Density, Poisson's Ratio etc. I am tempted to add space in the article and leave the values empty - could spark someone to edit it, but I supt; if you would like to see a section on the subject included, at least provide seed information that others can build upon. --Cheers, Folajimi (leave a note) 15:37, 27 September 2006 (UTC)

Cylinder glass predates Blenko by 150 or more years
The Broad, Cylinder, French or German technique for making window glass is illustrated in Diderot's Encyclopedie (circa 1750-70), and can probably be dated to much earlier than that. I will try to dig up some earlier references. As an earlier author suggests, Blenko started working in West Virginia no earlier than the 1920s(?) Ids135 04:05, 22 July 2005 (UTC)
 * Now corrected in article Parasite 06:37, 4 February 2006 (UTC)

9 pound crown glass. ??
Question about 'crown glass process' - 9 pounds seems so - so - so random. Are there technical reasons (does it make a nice, 5' diameter circle?)? Otherwise this is a neat article which I hadn't bothered to read yet! I love the glass-flow section. I've been to the Corning Glass Museum where they not only deny it categorically but go to some length to stamp out the idea with very nice displays.--MichaelTinkler

==Would like to see some discussion of industrial uses of glass, such as for fiber optics (a very important use) and as an insulator. jimaginator

Egyptian priority for glass
I'm not convinced by the Egyptian bit. They would not have been able to melt sand on its own (despite its ready availability!) so at the very least they must have added soda. It also seems extraordinary that they appear to have invented the float glass process millennia before Pilkington Glass of St Helens. jimfbleak 15:56 9 Jun 2003 (UTC)


 * The ancient Egyptian glass (circa 1500 BC) is a soda-lime-silica glass that is not that different compsitionally from modern container and plate glass manufactured today. The soda was derived from littoral natron (hydrated sodium carbonate) in which lime and magnesia were impurities.  The first applications were as simulated gems then rudimentary containers. Reference: Kurkjian, Charles R. and Prindle, William R. (1998). Perspectives on the History of Glass Composition. ''Journal of the American Ceramic Society, 81 (4) 795-813.--tod 05:59, 29 Jul 2004 (UTC)

Egyptian float glass, 1998 plant
Mott MacDonald (http://www.mottmac.com/html/01/01_05_afr1.cfm) claim the credit for "Egypt's first float glass plant, opened in 1998". Perhaps someone should tell them! -- Heron

flow=/=creep. True or not?
What is exactly the difference between "flow" and "creep"? Is it a matter of linearity of response? And then tar pitch: how is this different from glass? Isn't the fact that tar pitch flows and glass doesn't a quantitative rather than qualitative difference? -- T


 * Flow and creep are two different ways of looking at the same physical phenomena
 * The creep function describes the relation between stress and deformation
 * In other words creep is related to time dependent elastic constants
 * The word flow is usually applied to systems with constant viscosity
 * Here the word viscosity describes the relation between stress and deformation rate

3 improvements
Three things: 1. Nowhere do I see a broader definition of glass (non-crystalline solid) - this SHOULD be mentioned! 2. Everything flows at sufficient pressure/force (or decomposes). 3. Comparing glasses of different ages (eg Modern vs Egyptian) is spurious unless the chemical composition and the heat treatment is identical.DEN/3/13/2004

ASTM definition and comments
1. A broader definition would complicate and confuse the article. All glasses are non-crystalline (syn. amourphous) by definition. However, not all non-crystalline solids are glasses. Non-crystalline is a more general term. A definition would be good though. One possibility is the ASTM definition: A glass is an inorganic product of fusion that has been cooled to a rigid condition without crystallization. Translation: A glass is material (not based on chains or rings of carbon atoms) that has been produced by melting a liquid that was subsequently cooled to solid form without forming crystals. Note that in addition to being non-crystalline, a glass is not a polymer (plastic) but can be a metal. There exist non-crystalline polymers (i.e., polycarbonate, polymethylmethacrylate (plexiglas)), not a glass. And non-crystalline metals (metallic glasses) which are a glass. Also a glass must be formed from a molten liquid. Therefor this definition would exclude non-crystalline materials produced by other such as vapor deposition, oxidation, grinding, radiation exposure. For example, fused quartz is a pure silica glass produced by melting quartz sand and is a glass. The non-crystalline silica produced by oxidizing a silicon wafer in computer chip manufacturing is not a glass. 3. see comment above. --tod 05:59, 29 Jul 2004 (UTC)

Statistical physics definition
1) In statistical physics the word glass is often used to describe a disordered system that has been cooled to a temperature where the dynamics of the system is slow compared to a given experimental timescale. Experimentalists will typically compare the relaxation time with a timescale of 100s, whereas a computer physicist will compare to much shorter timescales.In this respect the word glass is used to describe a range of systems including polymer, molten metal, supercooled organic liquids as well as the spin glass. Sometimes the term glass is used to emphasize that a system that has been kinetically trapped in a non-equilibrium state, but in other cases the term glassy response is used to describe any fast response of a viscous liquid at equilibrium. Sometimes the term ideal glass transition describes a hypothetical low temperature second order phase transition in supercooled liquids. (anonymous coward. 2 aug 04.. just added some links 17 oct)

more on 'flow=/=creep'
When a solid "creeps," this refers to a permanent, plastic, time-dependant deformation that usually relies upon some applied force *usually* at high temperatures. (Think of centrifugal forces on a nickel-base turbine engine blade.) Creep for crytalline solids is heavily dependant on things like dislocations, difussion constants, Burgers vectors, and others. Flow, however, is more poorly understood for glasses. There exists only a very fine line between creep and flow, and sometimes to avoid addressing the issue, the literature will talk of "time-dependant flow" of glass. Flow depends heavily on viscosity, which is a very non-linear variable related to a exponential function of temperature. An added level of indirection is the *type* of flow, be it Newtonian or non-Newtonian, which relates to strain-rate effects. Those are questions better asked to a fluid-mechanics expert instead of a materials scientist, though.

Flow is failry well understood for glasses. Molten glass in general pretty much behaves as a newtonian liquid. The temperature dependence of viscosity is common to most all liquids. Near the glass transition temperature it is viscoelastic (which arguable can be complicated, but known), below it is an elastic solid. There are two additional situations that complicate things further. One is flow under very high strain rates as may occur during very high speed fiber drawing or very high speed press and blow manufacture (i.e. bottles). You then can run into shear thinning, a non-linear viscosity effect. Second, occurs if the particular glass composition is susceptible to phase separation (think oil and water). --tod 05:59, 29 Jul 2004 (UTC)

Toughened and laminated glass; catastrophic failures
Re: toughened glass and laminated glass - there's no mention of a specific issue I've heard of. With large plates of toughened glass used for walls and ceilings, is there not an issue with "catastrophic failure"? A bad batch will just suddenly shatter one day, or one by one over a few days? I had heard of this as a reason for laminated glass being a safety measure - a form of backup. Is this nonsense or is it something that should be included - I don't know any facts bar what I've described. Zoney 14:23, 21 Jul 2004 (UTC)


 * For this reason laminated toughened will sometimes be used - the toughening process gives the glass its strength, while the PVB laminate will hold the glass in place in case of failure. 


 * Also, there are restrictions on where toughened glass should be used - for example, in Australia it can not be used if not if the glass could fall from a 10m height above a trafficable area when shattered.


 * A destructive testing process called "Heat Soaking" is used to minimise spontaneous breakage. Toughened occassionaly shatters for no apparent reason, mainly due to nickel-sulphide inclusions.  To reduce this risk, glass can be heated after toughening (but not greater than the annealing point).  This causes any panes with nickel-sulphide stones to shatter, and the remainder are safe for use.


 * --Parasite 06:27, 16 Aug 2004 (UTC)

material properties of tempered glass, fiberglass
NB: Tod's comments below. This account is 'still' correct, just inverted as to compression placement at room temp. It's an important point, though. ww 16:17, 4 Aug 2004 (UTC)
 * The article speaks of toughened glass and this is perhaps a misnomer. An alternative term (also a misnomer in respect to tempering in ferrous metallurgy) is tempered glass. In either case, the fast cooling has the effect of solidfying (though in glasses this is itself a bit of a problem) the surface while the interior is still molten. In most glasses, solidification results in a contraction as for many other materials. This means that the outer layer of the piece goes into tension, while the inner mass (still not 'solid') is placed in compression. This situation continues even after everything has reached room temperature.


 * Now consider a break in the surface layer (still under tension even at room temp). The tendency will be for the break to propagate (much more so than for normal glass, which is itself quite willing to pass a crack along rather rapidly) and for the interior, being quickly relieved of its compressive strain, to expand. The result is an almost explosive release of both tension and compression and an extremely prompt shattering of the entire mass. It is indeed a catastrophic failure and if anyone was so foolish as to rely on that piece of glass for structural support of anything, well.... Even when the only structure being supported is the glass itself, the stuff is dense and can cause problems merely falling to rest if it's up in the air somewhere when it fails. Glass is not a sane structural material. But this is a good thing in some circumstances as small bits of glass are far less dangerous than large hunks, especially large falling hunks. The stuff has sharp edges, and small and light sharp edges are much less dangerous than large and heavy sharp edges when they connect with cuttable skin and eyes and ...
 * There are also ways to 'case harden' glass objects rather analogous to case hardening in metal work. These employ chemicals and mild heat to produce a tougher surface layer. One or another of these is common in treating glass spectacles for increased resistance to scratching and such. It is NOT the same thing/process as the forcible cooling business discussed in the article and above.
 * And now someone will surely ask, "what about fiberglass? Does not the glass fiber provide the strength in that stuff? Surely the binder does not, it has poor strength and toughness either in tension or compression?" And the answer is, yup, that's so. The difference is that glass is actually rather strong in tension, but never exhibits this strength in the usual case (eg, windows encountering baseballs hit by youngsters) as even minute scratches provide a focal point for strains and so are a failure waiting to happen when even the smallest additional strain is added. It's why glass is called 'brittle'. Properly produced and applied glass fibers retain much of that strength, are protected from more such scratches by the binder material in fiberglass, as well as constrained to be here and not there when the load appears, and are actually quite useful under some loading conditions.
 * This aspect of glass is notably missing from the article, but involves so many additional considerations (eg, failure modes, strain concentrations, etc) that I'm at a loss how to add it w/o too much increase length. Ideas anyone? ww 15:21, 23 Jul 2004 (UTC)

not too long, just add it

 * I would recommend just adding it, possibly under "architectural glass" - what you have written is fascinating and would make an excellent addition to the article. Length is not really a problem, certainly not for material this topical (it answers questions like "Why is broken glass dangerous?" "How do they make car windows safer?").  The fibreglass stuff might should go here in summary only and into the fibreglass article in detail, but your comments here certainly seem very apropos. --Andrew 19:08, 23 Jul 2004 (UTC)
 * A, One of the reasons car windows are safer is the multiple layer nature of (windshields in the US, I don't know elsewhere) as the plastic internal layer hangs onto all (most, anyway) of the sharp dangerous pieces and keeps them from flying about cutting this and that important thing. You generally get a drooping layer of plastic with sharp bits stuck to it. Much safer, if not entirely safe, and a better deal all around. Better still, of course, is to stay out of accidents altogether. ww 16:17, 4 Aug 2004 (UTC)

surface in compression in tempered glass, not interior
While you are correct that 'toughened glass' could be considered a misnomer (toughness has a specific meaning with regard to the strength of materials), tempering glass is not. In fact there are two ways to temper glass to increase its strength: thermal and chemical. Regarding thermal tempering, you are incorrect that the surface of a glass is in tension even at room temperature. On initial cooling you are correct that the surface is in tension and the interior is in compression. However, below the glass transition temperature the stresses reverse and the surface is in compression and the interior is in tension increasing the strength of the glass. Prince Rupert's drops are a laboratory curiousity demonstrating this phenomena. If a drop of molten glass is cast into a container of water, it solidifies into a shape roughly resembling a tadpole. You can bang on the big end with a hammer and the glass drop will not break. However if you nip the tail, the drop disintegrates into dust usually with a pop. Thermal tempering is usually applied to windshields. Chemical tempering is usually accomplished by ion exchanging a smaller atom for a larger atom at the surface again putting the surface in compression. Although glazing and surface crystallization can also be used. For example, soda-lime-silica glass can be placed into molten potassium nitrate and exchange potassium for sodium in the surface increasing the strength of the glass. Thermal tempering can increase the strength of glass from 70 to 200 MPa while chemical tempering can increase it 500 to 700 MPa. Chemical tempering is commonly used to increase the strength of beverage containers. --tod 05:59, 29 Jul 2004 (UTC)
 * Tod, You know, I've played with that tadpole drop thing, and had completely forgotten it. I stand corrected, ouch. I was inverted. And Prince Rupert's drops are a great WP article. I encourage you to creat it if it doesn't yet exist. ww 16:17, 4 Aug 2004 (UTC)

Ultraviolet transparency confusion

 * Most ordinary glass is opaque to ultraviolet light with wavelengths shorter than about 380 nm, though special glasses are made which have less transparency toward the ultraviolet.

This sentence from the article seems to be self-contradictory or confusing. Someone other than me ought to fix it. --Yath 05:49, 26 Jul 2004 (UTC)


 * I am really confused. A simple experiment will show the reason why greenhouses are built of glass.  1)Put a sheet of ordinary window glass between your face and the sun; you will still feel the solar radiation. 2)Put the same sheet of glass between your face and a barbeque grill; you will be shielded from the heat.  Conclusion?  glass is relatively transparent to ultraviolet compared with infrared.  Will someone with more knowledge than I have please explain the discrepancy?  Too Old 17:04, 17 Sep 2004 (UTC)
 * Yes you can feel the solar radiation through glass. But since most of the power is in the visible, that would be true independent of whether or not it passed any ultraviollet at all. The conclusion you have doesn't follow from the given experiment.  The correct conclusion for that experement (if the facts are as reported) is that glass is more transparent in the visible than in the infrared. Nahaj 01:52, 23 April 2006 (UTC)

about UV/IR transparency

 * Heat is transmited by convection/conduction as well as from radiation. In your experiment, the glass sheet shields you from the *hot air* coming from the grill. This is not relevant in experiment 1, where air at both sides of the sheet is at the same temperature. -- T

due to poor precision in terms used; too common in article
This confusion probably arises from the undefined term 'ordinary glass.' I suspect what was meant was the family of glasses based on the 1:1:6  soda-lime-silica composition (roughly 14 Na2O, 12 CaO, 75 SiO2 on a weight percent basis) that is nearly ubiquitous in the manufacture of clear container and window (plate) glass. The UV cutoff wavelength of glass is primarily composition dependent. Pure silica (100% SiO2) glass can have a UV cutoff below 200 nm, while glasses containing, for example, ceria (CeO2) or titania (TiO2), will shift the cutoff to wavelengths below 380. If enough of these oxides are added the cutoff will shift to wavelength below 400 nm which will manifest itself as a coloration of the glass as the blue end of the visible spectrum is absorbed along with the UV.

Which brings up my main criticism of the article. There are many instances of vague or undefined terms such as 'common', 'pure', and 'ordinary' that can be confusing without context. --tod 05:59, 29 Jul 2004 (UTC)

Agreed, why do we mention cerium as preventing UV stuff, when it said it blocks all, etc... Some clarity on this would be nice. -- ~ender 2005-02-13 11:18:MST

Addition by anonymous user
Here is the diff. I removed it not because I thought it was accurate or inaccurate, but because this thing is going to be on the main page tomorrow (Sep. 17) as a featured article and I'm not comfortable trying to rework or incorporate it in such a short amount of time. Can someone else tackle this? --Ardonik.talk 19:32, Sep 16, 2004 (UTC)
 * Well, I was the one who put it in - I am a glassblower. But what I find interesting is that any corrections I have made simply disappear.  For example, if this is a feature page - William Blenko did not invent cylinder glassblowing in the early 1900's, it was used decades before - yet the misinformation appears nice and clean on a feature page.

Crystal? (glass with lead-oxide)
I don't see any mention of crystal glass in the article, and I don't quite know how I could fit it in, does anyone care to do so? 3:56 UTC 17-Sept-04

Is the flowing question contraversial?
The heading 'Arguments against glass flow' seems to imply that the question of glass flowing is contraversial. If this is the case, the article should make that more clear IMHO and have a "for glass flowing section". If this is not the case, the heading should reead "Evidence against glass flow", not "Arguments" Bletch 12:32, 17 Sep 2004 (UTC)

liquid?
Okey, glass is not flowing.

But is it a liquid? I think that, but I am not sure. But it would be important to include that in the article (whether or not it is) It _is_ a liquid if there is no first order phase transition between room temperature and high temperatures, and the decrementation of viscosity is continual.

So..?

It is my understanding that glass is indeed a liquid. Glass knives are frequently used to process samples for electron microscopy. Only freshly made knives are sharp enough due to the liquid nature of the glass.


 * Try using fused quartz instead. Flint glass undergoes some (highly localized) dissolution in water, because of minute fluctuations in sodium and calcium content: this is probably what causes your knives to dull.--Joel 00:36, 24 Apr 2005 (UTC)

My understanding is that glass is a liquid at room temperature. The arguements that older glass (Midevel, etc.) are irrelevant as the flow rate is so low that event that time frame is not sufficient for the glass to lose its shape. Its a liquid we treat as a solid, but that doesn't make it so. Bismuth is radioactive, but at least one isotope we treat as if it isn't (sorry, I can't remember which one). It's half-life is much longer than the age of the universe, but it is radioactive. I encourage the reader to check out the Straight Dope Archives on this one at glass which I'm going to add to the main article. Rt66lt, August 5, 2005


 * Not a physicist or chemist, but I've seen it said glass is "extremely low viscosity liquid". Comment? Trekphiler 05:27, 9 December 2005 (UTC)

For what its worth, one of my chemistry professors at UC Berkeley referred to glass as a liquid in passing and it struck me as odd so it stuck with me. Also, I've seen documentaries on the world's largest telescopes (located in Hawai'i and owned by the UC system as I recall) which noted that larger lenses were impossible to make since the glass would "pour" and distort images too much. BoomBox 17:08, 7 January 2006 (UTC)

Liquid vs glass - terminology
If you wish to discuss if glass is a liquid, then you must use the terminology of glass physics.

1) The wikipedia page defines liquid to be one of the four phases of matter. This definition is of course correct and very useful, but it does not apply to silicate glass at room temperature. The problem is that if you define the word liquid in terms of a phase diagram, then you are only able to treat equilibrium states.

2) In glass physics a sample is usually defined to be liquid if the viscosity is smaller that 10^12 Pascal seconds, or if the ratio between viscosity and instantaneous shear modulus is smaller than 100s. These definitions are practical as they allows you to compare the glass transition temperature of different chemical compositions, and I pressume that they are also used in the glass industry. Strictly speaking the term viscosity is an equilibrium property, and therefore the viscosity of a non-equilibrium states is only welldefined within models. However I still think that it is fair to use this definition to rule that silicate glasses at room temeprature are not liquids.

3) You asked for a thermodynamical definition: Sometimes the term liquid is used to describe a sample at equilibrium, whereas the term glass is used to described a system that is frozen in a non-equilibrium state (Here I mean frozen within a suitable experimental timescale). In other words the term glass is usually defined to be the opposite of a liquid. It is correct that in a phase diagram the boundary between the liquid phase and the glass phase is not a phase transition. Instead it marks the temperature where the system leaves equilibrium. (Actually it is very dangerous to draw this kind of phase diagrams, because the boundary between liquid and glass depends on the cooling rate). Anyway silicate glass at room temperature has been frozen in a non-equilibrium state and therefore it is not a liquid.

BTW: The article describes that additives are added to lower the melting temperature. I don't think that this is correct. The the word melting temperature refers to the temperature at which the system can crystalize. In other word the sample is supercooled whenever it is cooled below the melting temperature. HOwever temperature is unimportant for the production process, so there is no reason to try to change it. I would pressume that the additives are added to lower the Glass_transition_temperature.

The article seems to imply that silica glasses are not supercooled at room temperature. I have a feeling that this is wrong. At least it is inconsistent with the claim that system has a melting temperature of 1000 K. The sentence should probably be double checked or deleted.

UV Radiation
The article describes the ability of some glasses to block UV light, which is parenthetically described as "ionizing radiation." It is my understanding that the term 'ionizing radiation' usually applies to high-energy particles resulting from radioactive decay, or electromagnetic radiation at frequencies higher than UV, such as x-rays or gamma rays. Although the article is correct in saying that UV may be biologically harmful, it may not be accurate to describe the UV blocked by glasses as 'ionizing radiation.'
 * No, ionizing radiation is anything with enough energy to ionize an atom/molecule, i.e. to break a bond. Look at Ultraviolet for confirmation that UV does indeed have this property.  You're right, however, that most other forms of ionizing radiation are more energetic, and many can pass through glass quite easily, especially if there's no lead or uranium in the mix.--Joel 01:08, 24 Apr 2005 (UTC)

Melting point additives
Hello. As a casual reader, I find the following two statements a little confusing. They do not seem to be consistant:
 * From the 3rd paragraph in the introduction: Pure silica has a melting point of about 2000 °C (3632 °F), so two other substances are always added to the sand in the glass-making process. One is soda (sodium carbonate Na2CO3), or potash, the equivalent potassium compound, which lowers the melting point to about 1000 °C. However, the soda makes the glass water-soluble, which is obviously unhelpful, so lime (calcium oxide, CaO) is the third component, added to restore insolubility.
 * From the 3rd paragraph in the Overview: Sodium is generally used to lower the otherwise impossibly high (when glass was first discovered) temperatures needed. Additional soda or potash is sometimes added to further lower the melting point.

I think this should be cleaned up. I don't know anything about glass making, so I am not making this change. -- JamesTeterenko 22:33, 17 Sep 2004 (UTC)


 * I gave it a once over. See what you think.--Joel 01:24, 24 Apr 2005 (UTC)

Supercooling is not relevant to whether or not glass flows
The melting points of various kinds of glass are wellknown. Therefore it is well known that all glass is supercooled at room temperature.

It is not controversial to write that glass is supercooled at room temperature is supercooled. It would be wrong (and thus controversial) to say that windows glass is a liquid at room temperature. The information of glass being supercooled It is not relevant to to question of whether or not windows flow.

Please remove the part about amorphous solids
The introduction of the article is inconsistent. First you write that glass is transparent, and then you write that the term glass is used to describe any substance thats is cooled below the glass transition temperature. This definition also includes some liquids that have a color. Later again you introduce terms like common glass and ordinary glass without definition. How about adding the following sentence instead.

"In physics the term glass often refer to an amorphous solid or a liquid that is cooled below the glass transition temperature." --- Following the format of other Wikipedia articles, I moved the physical definition of a "glass" to the top, gave an example, then stated that the remainder of the article is concerned with the common definitiono f "glass"

Self-cleaning glass
I've just noticed that the section on Self-cleaning glass starts: "A recent innovation&mdash;once more from Pilkingtons" yet there are no other references in the page to Pilkingtons. Is this a reference to something that was once but is no longer in the article; a subtle peice of self-advertising; or something else entirely? 192.171.162.101 16:28, 31 Jan 2005 (UTC)


 * Well Alastair Pilkington is famous for the invention of float glass. Both he and the family business are in fact mentioned in that section.
 * I think the problem is that the company may have changed its name several times over the past couple of decades. I'm pretty sure it used to be called Pilkington Glass and it now seems to be just Pilkington, but there is a good chance that it was called Pilkingtons with the extra 's' some time in between (not that the article on Pilkington Glass tells you much). -- Solipsist 17:36, 31 Jan 2005 (UTC)


 * Thanks for the info! I've replaced "Pilkingtons" with "Pilkington Glass" now; hopefully I'll be the last person confused by this :O) (the same person, now no longer at work) -- Whitepaw 19:29, 2005 Jan 31 (UTC)


 * Pilkington Glass are based in St. Helens (my hometown), and as a "short" they are known as "Pilks". As in "something is going on at Pilks".  In the same respect "Pilkingtons" is used when referring to something they're doing or is happening to them.  S'just a colloquial habit. Koncorde--82.42.56.236 17:51, 22 May 2006 (UTC)

flow sentence argument thing
"This section is an argument in favor of a position; it does not belong as part of a reference work. The statement that glass is a supercooled liquid refers to the lack of a specific melting point for glass, not to any perceived rate of 'flow', so the argument that follows is meritless."


 * I want to remove this sentence, but I imagine there might be some controversy behind it? - Omegatron 00:05, May 16, 2005 (UTC)


 * No harm in toning down the rhetoric to be less aggressive. If that editor comes back and yells "I wanted it to make prior editors feel like dirt!  It has to be worded my way!  Change it back, you moron!" then it will be safe to remove the statement entirely.  One thought is that you might reword it to clarify that the argument is meant to combat the common misconception that old panes of glass have flowed since installation etc. etc.--Joel 07:57, 16 May 2005 (UTC)

It was changed by someone else, but a bunch of information was removed? - Omegatron 17:35, May 18, 2005 (UTC)
 * The fact that glass "creeps" doesn't really belong in the room temperature flow argument, because (as a previous editor neglected to mention) creep is a response to high temperature as well as stress. From the standpoint of fundamental physics, it is the same glass-transition behavior discussed above.  We can probably debate about the suitability of newsgroup discussions as reference material, however.--Joel 18:12, 18 May 2005 (UTC)


 * aha! there are two different types of movement being discussed!  this should be more obvious, methinks. - Omegatron 19:42, May 18, 2005 (UTC)


 * I was the one who removed it. I rewrote the whole section. I was being bold. Change back whatever you think I overstepped. moink 03:39, 19 May 2005 (UTC)

The new section title, "The myth of glass being liquid at room temperature", seems clunkier than the previous, "Does glass flow?". &mdash;wwoods 23:15, 18 May 2005 (UTC)


 * Yeah, it's clunkier but more accurate (i.e., there's no real debate). Change it to something simpler if you like. moink 03:39, 19 May 2005 (UTC)

Edited introduction
I've edited the introduction to the article (mostly new headers and a reorder of some material) to make it easier to read. Also there was some repetition of information and a little too much detail in the first section. Possibly still needs some work though. clare