Talk:Glass

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[edit] History of glass

There is a historical inaccuracy in this article: "After the fall of the Empire, the Emperor Constantine moved to Byzantium where the use of glass continued, and spead to the Islamic world, the masters of glass-vessel making in the later Middle Ages." The Emperor constantine did moved to Byzantium long before the Western Empire collapsed-not to mention the fact that the Empire endured in the east. —Preceding unsigned comment added by 142.68.45.36 (talk) 22:19, 30 September 2007 (UTC)

Removed this innaccuracy Jdrewitt 13:36, 30 November 2007 (UTC)

[edit] Strength of Glass

In the introductory paragraph there is a statement about glass breaking into shards implying that it is weak in tension and strong in compression. This will lead the reader to understand that glass is a weak structural material in tension. My understanding is that glass can be a very strong material in tension and that is why it is used in fibre reinforced plastic, for instance. I suggest this statement be replaced with a more factual general statement about glass material strength properties. The property of breaking into sharp shards is probably more complex than a simple statement about tensional vs compressional strength can capture, without being misleading.

Mike —Preceding unsigned comment added by 207.189.247.235 (talk) 16:33, 10 October 2007 (UTC)

I removed this statement in the introduction as it is a little superflous and as you suggest not necessarily accurate. This information would also be more suitable in the properties section. Jdrewitt 18:10, 10 October 2007 (UTC)

[edit] Quick-failed good article nomination

Per the quick-fail criteria of the GA process, any article with cleanup or expansion banners and tags such as {{fact}} must be failed without a hold period. Please feel free to renominate the article when the necessary improvements have been made. Other major issues that would need to be dealt with include the following:

  • The prose is, for the most part, a pleasure to read. However, the article needs some work to comply fully with the Manual of Style. At present, the lead section is not a concise overview of the entire article. It only provides a basic definition of what glass is and how it's made. Expanding into a second paragraph which succinctly summarizes the rest of the article is necessary. Another issue is the use of blockquote formatting for quotations of less than four lines. This is improper per the MoS, and needs to be corrected. The sections Renaissance glassmaking, Industrial revolution glassmaking and Market structure also need serious expansion or merging in to larger sections.
  • Another area lacking is inline citations to references. Presently, every section in the article has large portions of text (i.e entire paragraphs and even subsections) that contain no inline citations whatsoever. The minimum for GA status would be a single ref at the end of the paragraph and for quotes. More, such as for potentially controversial statements, would be desirable. Remember that cites should always come after punctuation, not within it. This is especially true when citing quotations (such as in the bulleted list within Behaviour of antique glass).

Thank you for your work so far. If you feel this decision was in error, you are welcome to ask for a reassessment. VanTucky Talk 21:07, 27 October 2007 (UTC)

[edit] Contradiction?

Under "Glass in buildings" the article states: "Glass has been used in buildings since the 11th century". But under "Romans" it says: "Window glass was commonly used during the 1st century BC". If this isn't a contradiction, it needs clarification.Sreifa01 (talk) 07:10, 21 November 2007 (UTC)

Are either statements cited? If not they should both go, there is no point of having statement like this just for the sake of it. Jdrewitt (talk) 20:58, 21 November 2007 (UTC)

Both statements "Glass has been used in buildings since the 11th century" and "Window glass was commonly used during the 1st century BC" seem to be correct. I will look for a reference. It resolves the contradiction if the first statement is considered only for medieval Europe, and the second one is considered to be general.--Afluegel 14:11, 2 December 2007 (UTC)

[edit] See also section

A few points to be made here:

  1. The "examplefarm" tag may not be purpose-built for this section, but it serves the job. "See also" should not be a dumping ground for articles within the same topic; it should link to the most relevant links which for whatever reason can't be included in-article. The section should remain tagged until the problem is brought under control.
  2. "See also" is a pointer to articles. There's no hard in including anchors in the links if only a particular section of the linked article is pertinent, but they should be presented without piping to let the user know where they're being taken.
  3. Four columns, people. Many of these links should be covered by the article's category tags; category pages are the correct place for multi-column lists of relevant articles. We need not duplicate them here.

I believe most of these links can safely be removed, or incorporated into the article more directly. Chris Cunningham (talk) 12:09, 13 December 2007 (UTC)

The Wikipedia Manual of Style itself contains 15 links in its see also section, the links in the manual of style are also annotated which kind of makes the above comments slightly baseless. The links in this article are relevant to glass and therefore the tag is invalid and has been removed. A cleanup tag would be more appropriate (but still uneccessary) but the "examplefarm" tag is certainly NOT appropriate for the job Jdrewitt (talk) 13:48, 13 December 2007 (UTC)
I've re-tagged using a proper cleanup tag. WP:MOS has fifteen links; this article has thirty links and is half the length. Furthermore, WP:MOS serves as help documentation and can thus perhaps be forgiven for being comprehensive. I would ask again why you feel that these links should be included here when they are already collected within Category:Glass, which is linked in the article's footer. Chris Cunningham (talk) 14:16, 13 December 2007 (UTC)
Why not just delete the entire section then? It is obviously superflous when looking at Category:Glass Jdrewitt (talk) 15:16, 13 December 2007 (UTC)
That's an option, but it's quite a bit more drastic. If every current link is indeed already in Category:Glass then I reckon that's a good call. However, there may be articles related to the subject but not subsumed within it, and those are really the meat of seealso sections in my mind. Chris Cunningham (talk) 15:42, 13 December 2007 (UTC)
I deleted all links that are already contained in the Category:Glass page. For consistency, I suggest the remaining links should also be placed in the category page instead of being linked from the article Jdrewitt (talk) 16:15, 13 December 2007 (UTC)

[edit] Merge tag

Calumite and marvering are both one-sentence stubs. They could both easily be rolled into the manufacturing section. Chris Cunningham (talk) 14:25, 13 December 2007 (UTC)

Sounds reasonable to me. Teapotgeorge (talk) 15:02, 13 December 2007 (UTC)
I performed the merge, and redirected those pages appropriately. I didn't notice this has been a recent discussion, so I apologize if it was too soon. If any issues come up we can always revert everything and discuss. -FrankTobia (talk) 00:48, 14 December 2007 (UTC)

[edit] Refractive Index

At what wavelength are the values for refractive index taken in the glass properties tables? This should be specified as n is dependant upon λ Jdrewitt (talk) 11:38, 14 December 2007 (UTC)

The subscript D indicates the wavelength of 589.29 nm, see Fraunhofer lines --Afluegel (talk) 12:26, 14 December 2007 (UTC)
I think it would be wise to specify this in the article, all variables should be defined, even if they are in common use Jdrewitt (talk) 13:04, 14 December 2007 (UTC)
All right, I added a footnote. --Afluegel (talk) 17:03, 14 December 2007 (UTC)

[edit] Liquidus temperature

The Liquidus temperature is a very important property because, if not considered, it leads to crystallization and failure during production. Therefore, TL should not be deleted in the properties table. If possible, for most compositions TL should be stated.--Afluegel (talk) 12:30, 14 December 2007 (UTC)

That's fine, I deleted it because it wasn't known for many of the compositions but yes, was probably a mistake. I think we need to include the transmission properties and other optical properties which can lead into the discussion of the optical applications of some glass compositions. The other properties will be helpful to discuss why glasses are suitable for their own specific applications. Jdrewitt (talk) 13:02, 14 December 2007 (UTC)
Yes, the liquidus temperatures are important. I will try to find more TL data for the table. In case there is a reason to delete a column in the table I would start with the surface tension because the values are not very certain, despite they were measured and they are well referenced. Concerning transmission spectra there is one in the article soda lime glass, but unfortunately, without reference. -- Afluegel (talk) 17:18, 14 December 2007 (UTC)

[edit] Glass production

I think for the article to be good there need to be at least some technological details about industrial glass production, e.g., common commercial batch materials, batch preparation, melting in glass furnace, some forming techniques (incl. floating, blowing, pressing, casting), annealing, and surface treatments (tempering, ion exchange, IR coating) etc... The article Glass container production has some of the details needed, I think, but it concerns only glass containers.--Afluegel (talk) 21:40, 14 December 2007 (UTC)

I agree although this should also have it's own separate article as well (possibly merged with Glass container production). There is some info in the section glass production, this should possibly be renamed to industrial glass production (since some scientific glasses are made in much smaller quantities and don't necessarily require these bulk methods) and expanded although the full ldetails of glass production should be addressed in another article. Jdrewitt (talk) 08:50, 15 December 2007 (UTC)
I agree.--Afluegel (talk) 11:16, 15 December 2007 (UTC)
Yup, that's the right approach. Glass container production shouldbe moved to glass production and repurposed to cover both. Chris Cunningham (talk) 11:55, 15 December 2007 (UTC)
This may take several weeks to do... Anyway, its good to start step by step--Afluegel (talk) 16:27, 15 December 2007 (UTC)
I have created the page glass production although it needs much more work to be applicable to all types of glass production other than glass containers Jdrewitt (talk) 11:50, 16 December 2007 (UTC)

[edit] Order of sections

I think the current order of sections could be improved. For a layman there are two ways to get familiar with the topic because it touches his/her life:

  • A phenomenological explanation of common properties and uses. Everybody is familiar with it, and gets interested to read more.
  • The historical route. It is easy for layman to understand how glass was discovered, and how the technology evolved step by step. In this way a layman also may get interested to know more.

It is not a good approach, I think, to start out with the contemporary production process, or with a full-blown scientific discussion about the nature of glass. This is rather boring stuff for somebody who reads it the first time. However, it might become interesting after knowledge about common properties, uses, or the history. - By the way, this same order of topics is also followed in many high schools because it obviously has an educational effect. I need to have something first in my hand and feel it, then follow science, technology, and economy.--Afluegel (talk) 12:08, 15 December 2007 (UTC)

Yep. That's why I moved the section which at least describes glass's physical properties above the others. I think the problem we have is that the physical properties section starts off with prose and then includes a large table full of facts and figures which isn't very accessible to casual readers. I think what we should do is split this section into "characteristics" (the non-technical section, at the top) and "physical properties" (the table, further down the article). Chris Cunningham (talk) 12:13, 15 December 2007 (UTC)
The order could definetly be improved, however the article should certainly address (in laymans terms) what glass is at the start, since the article is entitled glass it's primary goal is to describe what glass is, properties, history, production, art etc are secondary (but are important none the less. Whether a topic is boring is a matter of opinion, the prose is generally fluent and coherent which is what counts Jdrewitt (talk) 15:22, 15 December 2007 (UTC)
I re-ordered the sections again, the positions are however by no means necessarily optimised, so may need some more work. Jdrewitt (talk) 15:53, 15 December 2007 (UTC)
You are doing good work. Now the article starts off easy, but also the deeper discussion and scientific understanding have their place for the advanced reader. In addition, maybe "Colors" could be moved to "Physical properties" or another place because it is not much related to commercial glass production or to glass making in the lab. The section "Silica-free glasses" could stand on its own, it is not well suited as a sub-section under "Glass production". Silica-free glasses are a wide field that does not go well together with common silicate glasses.--Afluegel (talk) 16:24, 15 December 2007 (UTC)
I really don't like the colors section as it doesn't really state what the base composition is. Maybe it would be more suitable in the glass art section? I agree with your comments about Silica-free glass Jdrewitt (talk) 17:09, 15 December 2007 (UTC)
It may be better off being moved to glass art in its entirety. But yeah, the current ordering is a big improvement. Thanks to both of you! Chris Cunningham (talk) 18:08, 15 December 2007 (UTC)
Yes some of the colors relate to bottles and so should also be incorporated into the glass container production section of glass production (once the page has been created) at some point. It's nice to have others willing to help improve this article, I've been working on it for a while but it needs to be a collaboration to work so thanks to both of you too! Jdrewitt (talk) 18:16, 15 December 2007 (UTC)
I agree. Thanks to you too.--Afluegel (talk) 18:22, 15 December 2007 (UTC)
I have moved the Colors section to glass art and added a sentence in glass container production as it seems more appropriate there. Jdrewitt (talk) 19:48, 15 December 2007 (UTC)
After thinking about the glass colors I believe they might be placed very well in the physical properties section of the glass article for the following reasons: 1) Colors are a physical property so characteristic for glasses that they are mentioned already in the lead section. 2) Glass colors are general properties that partially belong to bottle production, partially to float glass, partially to arts, and partially to optics (e.g., filters with sharp absorption edge). 3) The making of glass colors is partially an engineering topic, partially science (e.g. red CdS glass, photochromic glasses), and partially handicraft in arts. 4) Finally, in the glass article there is not much content yet about light interaction with glass, incl. transmission, absorption, and reflection, which should be improved, I believe. - I have a nice book about glass colors from the scientific and technological standpoint. It would be easy to add more content to the glass colors section.--Afluegel (talk) 10:08, 16 December 2007 (UTC)
Yes there should defintley be some comments on the colours in this article, but not the long list of additives that is now in glass art. I think the scientific explanations (that you have described) belong in this article but the 'recipes' belong in glass art or glass production. Jdrewitt (talk) 10:24, 16 December 2007 (UTC)
All right, I will try to move a small part of the colors section to physical properties, if this is OK.--Afluegel (talk) 10:45, 16 December 2007 (UTC)
OK Jdrewitt (talk) 11:01, 16 December 2007 (UTC)

[edit] First paragraph

I think we need to lose the chemistry detail. While I don't believe technical detail has to be avoided in an article lead, in this case the second half of the first paragraph is really pretty opaque (no pun intended) to casual readers. Of course if it can be rewritten to be more accessible that's an even better option. Chris Cunningham (talk) 18:55, 15 December 2007 (UTC)

I have edited the lead section, hopefully it is more transparent now? Jdrewitt (talk) 19:32, 15 December 2007 (UTC)
Quite a bit better, yes. We're really getting somewhere now. Chris Cunningham (talk) 19:36, 15 December 2007 (UTC)
Now there is quite a technical problem in the first paragraph. Most scientists consider sol-gel glass to be really a glass, also vitreous carbon (made by pyrolysis) is considered a glass and glassy metal. In addition: What is the difference between amorphous solid and solid glass?

By the way, the classical ASTM definition goes as follows: Glass is an inorganic product of fusion which has been cooled to a rigid condition without crystallization. - At least there is no distinction between amorphous solid and glass solid.--Afluegel (talk) 20:10, 15 December 2007 (UTC)

The term 'glass' is generally more restricted than an amorphous solid. The key is to pick a definition and clearly state this and then be consistent. Many people choose the definition of a glass as "an amorphous solid which exhibits a glass transition". The ASTM definition clearly distiguishes between forming a glass by quenching (whether it be melt quenching or deposition) and by other methods such as sol-gel (which is just a ploymerisation reaction) and ion implantation. Some academics regard 'amorphous solid', 'glass' and 'non-crystalline solid' as synonyms. However many do not. The more traditional concept of a glass, that is currently used in this article, is "an amorphous solid obtained by supercooling from the liquid state continuosly, i.e. without the first-order phase transition of crystallisation". In summary the term 'glass', is by convention reserved for an amorphous solid actually prepared by quenching the melt. The only mistake therefore is that maybe amorphous solids formed by vapour deposition may be classified as a glass? Jdrewitt (talk) 20:26, 15 December 2007 (UTC)
For the article to be neutral we can not get into a scientific dispute, but the lead section certainly is disputable, as you already said. Therefore, we could give the classical definition first, then mention sol-gel glasses (and similar "unusual" cases) and state that some scientists consider any amorphous solid to be a glass. We should not take any side.--Afluegel (talk) 20:39, 15 December 2007 (UTC)
I have now edited the lead section again and hopefully it clarifies the definition now. The rest of the article should now be checked for consistency in these definitions Jdrewitt (talk) 23:25, 15 December 2007 (UTC)
The definition reads now very well. Thank you. I think we can leave it as it is. We need to bring the first sentence under "Silica-free glasses" in line with it. - Then, in the second paragraph of the lead section are natural glasses, which could be moved as last subsection to "general properties and uses" because it is no so very important for a basic understanding. For this purpose, the section could be renamed to "general properties, uses, occurrence" or something similar. The sentence about silica-free glasses could remain in the first paragraph, or form the second paragraph on its own.--Afluegel (talk) 08:19, 16 December 2007 (UTC)
I did the adjustment, and moved also trinitite and beach glass accordingly.--Afluegel (talk) 19:18, 23 December 2007 (UTC)

[edit] Silica-free glasses

Carbon dioxide undergoes pressue induced amorphisation. Technically it is not a glass, but it does have the same disordered structure as a glass. For consistency this should be clarified or else be incorporated in the amorphous solids article instead. This is where strict definitions mess things up a bit since the structure of a glass and the structure of an amorphous solid are analogous Jdrewitt (talk) 20:07, 15 December 2007 (UTC)

The distinction between solid glass and amorphous solid is quite a mess, because I do not know how to do it in a clean way. The amorphous solid article may be merged with glass, or it may be stated in the glass article that it only considers glasses made by melting.--Afluegel (talk) 20:17, 15 December 2007 (UTC)
I think the only way to do this cleanly would be to suggest that CO2 has a 'glass-like' structure and then deal with the details of polyamorphisation either in a new article completely or within amorphous solid Jdrewitt (talk) 20:30, 15 December 2007 (UTC)
OK, you may move CO2. More important is to find a good and neutral first paragraph for the glass article.--Afluegel (talk) 20:42, 15 December 2007 (UTC)
Well...on second thoughts...Polyamorphism is also relevant in glasses. For example SiO2 and GeO2 undergo pressure induce co-ordination changes. And so I think CO2 defintely still has relevance here, we just need to sort out the definition, you have some good points about this above Jdrewitt (talk) 21:05, 15 December 2007 (UTC)

[edit] Quickly cooling or quenching required to form glass?

In a number of places, the article speaks as if rapid quenching is required to form glass, e.g.

By traditional convention the term glass is reserved for an amorphous solid which has been formed by quenching a glass forming liquid (or melt) through its glass transition temperature sufficiently fast that a regular crystal lattice cannot form

and

Solid glass is formed by rapidly cooling (quenching) the molten glass forming material.

and

The standard definition of a glass (or vitreous solid) requires the solid phase to be formed by rapid melt quenching

Although I know that some glasses require incredibly quick cooling (e.g. metal glasses), I'd thought that ordinary glass needed no special cooling, and in some circumstances (e.g. large telescope mirrors) cooling could occur over weeks and even months. If this is true, then perhaps these "needs to be cooled quickly" phrases should be changed to something like "needs to be cooled quickly relative to the crystallization time; although ordinary glass can be cooled quite slowly, some materials require extremely quick cooling." --Dan Griscom (talk) 00:09, 18 December 2007 (UTC)

You are right. Please go ahead and change it accordingly.--91.36.80.72 (talk) 20:00, 18 December 2007 (UTC)

The lead section already states that glass must be quenched sufficiently fast that a regular crystal lattice cannot form. This statement holds since the quench time must be sufficiently fast relative to the characteristic molecular relaxation time, so any timescale is valid here. However, the other sections could probably use some clarification as you have suggested. Jdrewitt (talk) 21:14, 18 December 2007 (UTC)
Fixes made. Jdrewitt (talk) 21:32, 18 December 2007 (UTC)

[edit] Glass definition

I think that glass should be better defined using four approaches:

  • Etymological definition: from glasa originating from the Germanic language family, meaning shiny, glossy and amber in the current English language. This original definition is still contained in the expression vitreous luster (from vitrum, lat. glass) for minerals, as well as in glaze and gloss.
  • Common sense definition: hard, brittle, transparent solid; The soda-lime glass specification does not belong to the common sense definition, because it is commonly only known the technical experts, i.e., it belongs to the technical definition.
  • Technical definition: amorphous silicate solid (soda-lime glass, borosilicate glass, fused silica, etc.) prepared by melting silica and other minerals, and cooling below the glass transition
  • Scientific definition: amorphous (usually inorganic) solid prepared by any method

The first definition is currently missing in the article, and the third and fourth are a little bit mixed.--Afluegel (talk) 21:32, 22 February 2008 (UTC)

I don't know about all of these definitions. I was using my dictionary as a source. Do you have a source for four definitions of glass? While it may not be commonly known that "common glass" is soda-lime glass, it's properties are well-known. So, to my dictionary and to me, the common sense definition is soda-lime glass and by analogy, similar substances. The scientific definition needs to have at least equal weight, since the whole point of an encyclopedia is to tell me what the word glass 'really' means. I have never heard of an "etymological definition"-- maybe we could have a section about "etymology". MisterSheik (talk) 22:35, 22 February 2008 (UTC)
The introduction is quite fine as it is. It just can be improved, especially for common readers that are not familiar with the topic, i.e., the educational and informative value can be improved.
  • An expression should not be explained with a more complicated expression, I mean glass should not be explained with soda-lime glass glass, but better with window glass or flat glass or container glass. Windows are very well known, as are containers and the expression flat. The technical term soda-lime glass can be introduced at a later point.
  • The technical definition goes as follows: Glass is an inorganic product of fusion which has been cooled to a rigid condition without crystallizing. (ASTM definition, 1945) In addition, according to reference 5 in the article (Vogel) most commercial glasses are silicate glasses. (Attention: The article silicate glass is currently not very good because it does not state that silicate glasses contain silica as main component.)
  • According to reference 5 in the article (Vogel), the term glass in the scientific sense is extended so as to include all amorphous (non-crystalline) solids, independently of the method of preparation. Currently, the technical definition is confused with the scientific definition. Just consider the current formulations: In the technical sense, glass is any amorphous solid, i.e., any non-crystalline solid. and In the scientific sense the term glass is often extended to all amorphous solids. One of the two sentences are not correct; they can not be valid simultaneously, as long as science and technology are not equal.
  • The etymological definition should be better formulated as etymological origin. It is given in the German article, but unfortunately, without reference. We need to look for it.
I think the common sense definition if given quite well in the above mentioned dictionary, but science and technology are not well understood.--Afluegel (talk) 13:35, 24 February 2008 (UTC)
Great work, Afluegel. I agree with you; let's replace soda-lime glass with window glass or container glass in the introduction. While I see the difference between the two definitions, I don't see the difference between "technical definition" and "scientific definition". Both definitions are technical and scientific, right? What do you think of "Tenchnically, glass is any inorganic amorphous solid, although sometimes glass is restricted to material that has been prepared by....etc."? Finally, let's for sure have a section called "Etymology" (origin is superfluous). MisterSheik (talk) 22:27, 25 February 2008 (UTC)
All right, I replaced "soda-lime glass" as suggested (and I introduced it just a little later). Yes, as soon as I find the reference for etymological details, I will introduce it. The term science is oriented towards basic, true understanding, while the term technique is oriented towards application and economy. Yes, of course, the two terms are often mixed in our times because scientists have economic interests and engineers obtain very useful results if they have a deep scientific understanding of the subject matter, but nevertheless, science and technology are not the same. I hope the current edits are fine. - By the way, it does not sound good to call aluminium oxynitride or isinglass as glass types. This makes only sense in connection with the common sense definition. Otherwise, aluminium oxynitride and isinglass are certainly no glass at all because they are not amorphous. --Afluegel (talk) 11:50, 27 February 2008 (UTC)

[edit] Solid or liquid??

From reading i have done about the structure of glass, there are meny descriptions that i would say clasify it as a liquid rather than a solid, one example if a website for this is [1] would anyone else agree? maybe a section could be added about it?

On the website you mentioned glass is not described as "liquid" without the terms "frozen" and "rigid". Please consider that "frozen" and "rigid" refer at the same time to a solid. I think it is important to understand that glass is certainly a solid by all common sense, but with the structure of a liquid, which is well described in the article. If you have a specific suggestion about the article improvement, please do not hesitate.--Afluegel (talk) 09:57, 8 March 2008 (UTC)
As Afluegel points out, the issue is already treated in the article Glass#The physics of glass Jdrewitt (talk) 19:20, 8 March 2008 (UTC)

This is just a comment based on my own experience with glass working. I believe glass is best described as a solid with a fluid structure. Like steel, a large enough piece of glass can deform "plasticly" under it's own weight; a process that increases with temperature. At normal temperatures this could take eons. Unlike steel, glass has no actual melting temperature, (never really turns to liquid), but rather acts like frozen honey, becoming more fluid, (or less viscous), as temperature increases.

The term liquid generally implies a fluid that can readily fill a container, so I think calling it that would be a bit misleading. A liquid is always a fluid, but a fluid is not always a liquid. 216.67.92.66 (talk) 22:07, 4 June 2008 (UTC) CLewis

That is not actually the case. Although when you form a glass from a supercooled liquid through the glass transition temperature there is a continuous increase in viscosity, the reverse does not happen when you heat up a glass. A glass exists in a metastable state with respect to the crystalline form of the same chemical composition. Thus, if you heat up a glass beyond its glass transition temperature, you provide the atoms with enough energy to re-arrange into the equilibrium crystalline state, you crystallise your glass and it is very much a solid. Further heating will result in a first order phase transition from the solid to a liquid. Jdrewitt (talk) 14:38, 5 June 2008 (UTC)

Thank you very much for your response. Yes, I agree, glass at room temperature is very much a solid. I simply think a lot of people's confusion comes from the fact that we're often taught in school that, at room temperature, glass "behaves as a liquid", when in fact it does not It behaves as a solid with a "fluidic structure". I merely think "fluid" is a better description, as "fluid" can describe a soild, liquid, or gas. (But, I yield to the experts on that.) 216.67.92.66 (talk) 18:04, 5 June 2008 (UTC) CLewis

Thank you too for your input here. The teaching in schools that glass is and behaves as a liquid is pretty disgraceful and demonstrates the ignorance of some high school teachers. Sorry, I didn't mean to oppose your entire comment, I was merely stating that a glass will 'melt' (i.e. undergo a 1st order phase transition at the melting temperature of the composition) like any ordinary solid. The structure of glass is certainly disordered and represents a liquid structure frozen into the solid state. But the fact that glass flows is clearly wrong, as you have already mentioned. I don't think the section Glass versus a supercooled liquid adequately describes both the similarities and the clear distinction between a glass and a liquid. The section Behavior of antique glass also attempts to dispel the myth that glass flows but I think both these sections could be made a little more coherent and readable to the layman. Any input from yourself on these two sections would be appreciated. Thanks Jdrewitt (talk) 20:15, 5 June 2008 (UTC)

No Problem. I'm happy to put my 2 cents in. My previous statement, that glass has no actual melting point, is clearly wrong. What I should have said is that the actual meltiing point of glass does not seem to be as clearly visible as, say, steel or ice. I guess if I were to try and define "melting point", I would say it's the point at which plastic-deformation gives way to flow. Or, in other words, the point at which two pieces that are touching no longer push against each other, but begin to readily flow, (weld), together. I think that definition could possibly be able to cover all solids making a transition to liquid.

A cracked piece of glass, at room temperature, could, theoretically, deform over a long enough time span, (ie: 50 Billion years or more), but since the crack will never weld together, I say that glass, at room temperature, can not be classified as a liquid.216.67.92.66 (talk) 18:12, 6 June 2008 (UTC) CLewis

[edit] Behavior of Antique Glass

This is just my observation of window panes that appear to be thicker at the bottom than at the top. Many of the panes that I've seen are not very old, but they are almost always very large panes, that are much taller than they are wide. What appears to be "thicker at the bottom", I believe, is really just the glass bowing slightly under it's own poorly distributed weight, which has a lensing effect. This is more likely due to the slow relaxation of the frame that holds it, allowing it to warp slightly below half its height. It is important to understand that flexing is neither deformation nor flow, as the glass, if laid down, would immediatly return to it's original flatness. 216.67.92.66 (talk) 23:35, 9 June 2008 (UTC) CLewis