Talk:Glass/Archive 4

Archive 1

Archive 2

Archive 3

Archive 4

Archive 5

Behavior of antique glass - fragility

Since we have a section on the "Behavior of antique glass", would it be worth including other aspects about the aging of glass? In particular, I believe I've read that very old glass becomes extremely fragile and may break even due to sudden changes in temperature. I've read about that in the context of ancient Islamic glass and also wine bottles over a century in age. Another aspect is chemical weathering, especially in glass that's been buried or underwater. Thoughts?   Will Beback  talk  23:38, 26 March 2009 (UTC)

Well, I personally have never heard of glass aging in such a way, but that doesn't make it not true. (The things of which I've never heard could fill the encyclopedia Wikipedia.) Do you have a source? If so, it may be interesting to compare it to the above theory that glass will eventually crystalize. (Excuse me if I'm wrong, with other wiki-projects going on, and real life, I haven't had a chance to read the new Physics of glass article yet.) Zaereth (talk) 00:45, 27 March 2009 (UTC)

Here's a paper on corrosion. "The Conservation of Ancient Glass". It references the Journal of Glass Studies and Conservation of Glass, which may be further sources. Here's an comprehensive article on the topic. "Stained Glass and Its Decay" I'm sure there are others.   Will Beback  talk  01:47, 27 March 2009 (UTC)

The key point here is chemical attack, glass is certainly subject to corrosion and chemical attack, SiO2 for example can be dissolved by HF acid, an extreme example but illustrative nevertheless. I'm sure some glasses will be subject to weathering erosion and some are certainly hygroscopic. There should be a section on glass conservation certainly mentioning its resistance or not to corrosion. Polyamorph (talk) 09:38, 27 March 2009 (UTC)

Agreed. After skimming through these, I've learned a lot I didn't know, such as glass getting waterlogged, or having minerals leached out of it. A section about this topic should definitely be included. Zaereth (talk) 17:21, 27 March 2009 (UTC)

Concerning glass corrosion I would like to refer to the article Corrosion, section Corrosion of glasses. Yes, it would be good to have a few sentences about corrosion in the article glass. I added it to the to-do-list on the top of this page. Otherwise, besides corrosion, glass does not age with time like plastics in the way that it breaks easier. Stresses might develop due to uneven temperature distribution (e.g., from the sun) which is reverted as soon as the temperature equalizes, and glass might suddenly break due to internal stress if a small fissure develops on its surface, caused by corrosion or impact. -- Afluegel (talk) 06:37, 28 March 2009 (UTC)

WP:GLASS

A glass task force is currently getting setted up. Contributors and members are very welcome! One of the initial tasks, I think, would be to improve the quality of this glass article to good article status (even if this might still take quite some time and work), considering the To-do list on top of this discussion page. Thanks. --Afluegel (talk) 06:49, 28 March 2009 (UTC)

Medieval Europe

71.198.39.215 (talk) 17:49, 28 March 2009 (UTC) What does Medival Europe have to do with Glass? 71.198.39.215 (talk) 17:49, 28 March 2009 (UTC)

The article is talking about glass manufactured in medieval europe - so quite a lot. Polyamorph (talk) 18:11, 28 March 2009 (UTC)

Article split suggestion

It seems to me that this article is plagued by trying to discuss two separate things that are topics in their own right. The first is glasses in general, and the second is silicate glasses. To be clear, the word glass actually has two different definitions. The first is the popular definition, which corresponds to silicate glass. The second is a technical definition, which corresponds to state of matter. Since there are two definitions, there ought to be a separate article on each. For example, since in the public consciousness glass is often synonymous with silicate glass, leading to some confusion. Silicate glass is so prevalent and such a large subject that it deserves a page of its own. For example, the entire history section discusses pretty much only silicate glass and not glasses in general. I also don't see any coherent way it could or should do both, as they are rightfully separate topics. I'd say lets split this into two articles, one called glass(silicate) and the other called glass (phase state) or something similar. Any thoughts? I'd be happy to do the gruntwork for the split, but as its a big change I'd like to solicit comment first. Locke9k (talk) 15:31, 5 April 2009 (UTC)

You certainly have a point about the topic, but still, I think it also would create problems that need to be well discussed:

• Some commercially important glasses do not contain silica. For example, the reflecting beads in the white pavement markings that are so well visible at night are titanate glasses, free of silica. (Unfortunately, the glass article does not mention them yet. If desired, a citation will follow.)
• What about non-oxide glasses, which are currently in the article? (see also Category:Non-oxide glasses)
• Even for common silicate glasses, the reader would still be interested in some physical background, and then we would end up in the same situation that we have currently.
• Actually, there exist already separate articles about the topic, e.g., Amorphous solid, Physics of glass or Glass transition or Phase transformations in solids. It just would be necessary to work on them. In fact, the article Amorphous solid talks mostly about silicate glasses, which I think it should not.

Personally, when I studied glass chemistry, silicate glasses and the glassy state of matter were well taught together, without any problem, at all universities I know of. Of course, we always need to be open to innovation, but at the moment I am still opposed to your suggestion. Maybe you could give more detail about it, and how the problems I mentioned could be overcome? I hope I understood your proposal correctly? Thank you for your input.

--Afluegel (talk) 21:28, 5 April 2009 (UTC)

Thanks for your response. You have made some very good points and I think I'll amend my proposal to address them. The article amorphous solid was exactly the kind of new article I was proposing to create in the split. Instead I am going to suggest a rename of that article (which I will bring up more appropriately over at that talk page). In general, I believe that the term 'amorphous solid' is synonymous with 'glass' it its technical usage. Furthermore, 'glass' is by far the more common term in technical use. However, that article presently shies away from that title to avoid confusion with this one. For example, it has the quote "The transition from the liquid state to the glass, at a temperature below the equilibrium melting point of the material, is called the glass transition." So in the text it acknowledges that it is talking about glasses even though it doesn't say so in the title. So basically I am going to amend my suggestion to some degree, which is that we should rename amorphous solid to be glass (amorphous solid state). We can then leave this article to focus on specific glassy materials, such as silicate glasses and the other important glasses you so aptly mention. However, to highlight the contrast with the other article, I think it might then be appropriate to rename this Glass (material) or something similar, to point out that this article is discussing specific glass materials whereas the other is discussing the phase state in general.

Let me also reiterate my objective here more clearly so that you maybe understand better what I am trying to do. Most lay people I meet do not understand that glass is a broad state of matter rather than simply the stuff they see in windows. For example, most people, when they say the word "glass", specifically do not intend to mean any 'plastics' (by which I mean the colloquial word for synthetic carbon polymers), despite the fact that many are in fact a glass. In my opinion the present structure of the coverage of these topics here compounds this confusion by discussing the two concepts as a unit rather than making clear that they are separate meanings of the word 'glass'. My suggestions are thus attempts to address this issue. Any thoughts on my updated proposal (subject to discussion at the other talk page)?Locke9k (talk) 22:19, 5 April 2009 (UTC)

Thanks for your suggestions, however, I think the current title is fine as it is. We have a seperate article for Silicate glass as we do for other glasses, e.g. Chalcogenide glass, and refer to these articles appropriately. Glasses and amorphous solids are not synonymous. The standard definition of a glass is a material that has been cooled sufficiently rapidly through its glass transition temperature forming a disordered solid via a supercooled liquid. Amorphous Solids may be formed by many other means and it is the amophous solids article that should deal with this. There is a sentence in the lead that addresses plastics and rightfully so wikilinks to the amorphous solids article. This article deals with glass in both the scientific and the commonsense and also discusses its history and uses, we really don't need to disambiguate the title. Glass as a state of matter is discussed in more detail in other articles. It is these articles which need input and work on, e.g. Physics of glass and then referred to where necessary from here. Polyamorph (talk) 07:55, 6 April 2009 (UTC)

Actually I don't really think that you are correct that there are other ways to form an amorphous solid. Can you name one? Certainly looking at the amorphous solid article the entire text is actually describing glasses. Also as I have mentioned, the present article does not deal with the history of glass as a state of matter in science. Instead it discusses essentially the history of glassmaking, which is a different thing entirely. Locke9k (talk) 14:37, 6 April 2009 (UTC)

Also, I'll ask you to look at the very first line of the intro of this article. It reads "Glass generally refers to hard, brittle, transparent material, such as those used for windows, many bottles, or eyewear." This is not even remotely the technical definition of a glassy material. Its exactly the lay definition for one. This is essentially my problem; this article primarily uses the lay definition of the word glass and then later suddenly decides to incorporate some discussion of the technical definition. One of the primary distinctions between wiktionary and wikipedia is that in wiktionary there should be one page of a word even if it has multiple meanings; whereas in wikipedia each meaning should have a separate page. There are certainly two meanings for the word 'glass', so it seems like it should have two pages.Locke9k (talk) 14:40, 6 April 2009 (UTC)

Splat quenching, Vapour deposition, Sol-gel, Polymerisation, ion implantation to name but a few. I am certain too not all amorphous solids will have a Tg. Amorphous solid needs work yes indeed as do a lot of articles on wikipedia. As I have already stated, this article attempts to deal with both the commonsense view of glass as a brittle transparent solid and aims to educate the reader of its other forms, uses and properties. Yes the article needs work, there are certainly ways this article can be improved but changing its name is not an option. Polyamorph (talk) 15:02, 6 April 2009 (UTC)

Ah yes, I understand your objection now. It is true that an amorphous material above its Tg should not be characterized as a glass. My apologies, I was in error in what I said above regarding there not being a nonglassy amorphous state - that was clearly silly and I'm not sure what I was thinking at the time. Amorphous solid clearly should not be renamed - that was a poorly thought out late night idea. Lets go back to the larger issue I made just above regarding the fact that in Wikipedia if there are two definitions there should be two articles. Do you disagree with that statement in general, or its applicability to this case? Locke9k (talk) 15:31, 6 April 2009 (UTC)

Well I would go along with the fact that we need two articles, one on glass as a material and one as glass as a state of matter. My point though is that glass as a material is already dealt with here and that there has to be some introduction at least into the physics of the material to make the article complete. Then if the reader really wants to read more than just an introduction then they should be referred to the article Physics of glass (a link already exists in the article to this effect) which is dedicated to dealing with glass as a state of matter. Polyamorph (talk) 15:47, 6 April 2009 (UTC)

I think we should name each article in such a way as most people use the words, including laymen and specialists. I mean, if somebody enters "glass" in the search box at Wikipedia, he is almost always looking for a common glass, I think, such as used for windows and bottles. Therefore, such a user it rightfully directed to this glass article, and not to the page Glass (disambiguation) with at least 20 other meanings. This article glass gives three definitions: the first for the layman, the second for the engineer, and the third for the scientist. Then, the rest of the article is mostly sticking with the second definition, which I think is the most popular, with a few exceptions in the glass physics section. However, I certainly agree with Locke9k that the general conception of glass in a physical sense is by far more fundamental than the current article glass, and therefore, such articles as Amorphous solid and Physics of glass should be appreciated accordingly, also through the name of the articles. I am not sure, if and how they could be re-named. The best way for finding this out, in case there is disagreement, is in my opinion to improve the content of the articles first and also creating redirects for synonyms. In addition, the articles Glass, Amorphous solid, Physics of glass are not always well aligned and the contens are not always cleanly separated.

Locke9k, also glass melts such as in a glass furnace are mostly termed as glass, even if they are above Tg and not solid. This is still partially missing or not clearly enough stated in the introduction, despite being mentioned in the second paragraph. I mean, glass melts are not only glass for a scientist, but also for an engineer and layman. I think we need to improve this.

--Afluegel (talk) 19:44, 6 April 2009 (UTC)

I would agree with that! Improving the current articles is the first thing to do. Creating redirects for synonyms is also a good idea to help people searching for a specific topic to get to the right place. Polyamorph (talk) 20:05, 6 April 2009 (UTC)

fictive temperature

"fictive temperature" should be an expression to be explained in these pages. —Preceding unsigned comment added by 145.64.134.242 (talk) 11:50, 29 May 2009 (UTC)

Vitreous state

Editors of this article may be interested in the discussion at Talk:Vitreous state, about what to do with the articles Vitreous state and Glassy state.--Srleffler (talk) 14:46, 27 June 2009 (UTC)

Input requested at Glass transition

The Glass transition article has been protected over an edit war that seems to have been building for some time apparently based on disagreement between 2 versions. (The current version is the one that happened to be live at the time of protection: no preference implied). Input is required from editors who are familiar with the subject to bring the article back on track. Please discuss on the Talk:Glass transition page. Thank you. Exploding Boy (talk) 02:53, 29 June 2009 (UTC)

I would be willing to help there. I have worked in a group specializing in glasses, but was never interested in the topic myself, which might help me being objective. If interested in my offer, could someone introduce me (or other potential helpers) to that war ? I have had sporadic experience with the edits of logger9 and Paula Pilcher yesterday (on other pages). With all do respect to them being professionals, they seem both deviating from WP rules. Materialscientist (talk) 03:39, 29 June 2009 (UTC)

Without wishing to make the issue about editors rather than content, a request was opened at Wikipedia:Wikiquette alerts and an uninvolved editor asked me, an uninvolved admin, to intervene in the developing edit war at Glass transition. I protected the page and temporarily blocked one user, however I have no understanding of the subject matter and can't tell which version (if any) is right. In addition, so far only two editors, the ones involved in the dispute, seem to have been involved in the relevant discussion. What is needed is some editors with an understanding, or at least a better understanding, of the subject matter to get involved in the discussion and assist with building consensus about what should and should not be included in the article. Exploding Boy (talk) 06:09, 29 June 2009 (UTC)

Is it safe to eat glass?

I'm really interested to know. Could someone find some well sourced information on this, and put it in the article, please? 75.53.94.232 (talk) 17:20, 13 August 2009 (UTC)

Yes, glass is inert. Even coarsely ground glass does not seem to be dangerous. But I wouldn't recommend eating shards of glass. —DIV (128.250.247.158 (talk) 10:12, 14 August 2009 (UTC))

"safe" as used by the original poster presumably does not refer only to its chemical properties but its physical properties as well. In which case "yes" is not an appropriate answer. A more accurate one would be "hell no". --86.168.72.216 (talk) 12:58, 4 September 2009 (UTC)

Of course its NOT safe to eat glass, there are many different types of glass with different chemical compositions, some of which are highly toxic. Not all glasses are stable and will react with water and other bodily fluids. Although not referenced, the disorder of eating glass is already dealt with in Hyalophagia. Polyamorph (talk) 09:25, 5 September 2009 (UTC)

Snopes.com has an article on the "ground glass will kill you" myth here. (I think they are referring to soda-lime glass.) Their conclusion was that the myth is false. Saunders Comprehensive Veterinary Dictionary corroborates this, as quoted here. I realize this discussion is a few years old but I thought it worth adding to the record anyway. 75.36.152.175 (talk) 01:05, 2 June 2012 (UTC)

Redundant

Article has "Those values marked in italic font have been interpolated from similar glass compositions (see Calculation of glass properties) due to the lack of experimental data." There don't seem to be any italics, so this should be modified or deleted. —DIV (128.250.247.158 (talk) 10:13, 14 August 2009 (UTC))

Thank you. Deleted. Materialscientist (talk) 10:23, 14 August 2009 (UTC)

Silica image

Please see the following discussion that has come to my attention regarding the silica image used in this article: Commons:Commons:Deletion requests/Images of silica. Polyamorph (talk) 22:41, 31 December 2009 (UTC)

Please also note the discussion here. Polyamorph (talk) 22:53, 31 December 2009 (UTC)

I'm not very happy about this. I created the image of the atomic structure of amorphous silica and it is a valid and accurate two-dimensional representation of the structure. However because of the limitations in drawing the structure in 2D the fourth oxygen atom around the silicon is hidden from view. This is where the problem arises because a user has proposed the image for deletion on the basis that it doesn't show 4-fold coordination. Of course silicon is 4-fold coordinated by oxygen in silica, its just that the fourth oxygen atom is hidden from view by the silicon atom. Please comment on the commons deletion page and help me save this valid and accurate image from being deleted. Thanks, Polyamorph (talk) 09:23, 1 January 2010 (UTC) P.S. Happy New Year.

For some reason this deletion request is still open, I can't fathom why except that I think deletion requests last a lot longer on commons. If anyone feels like commenting please do so, to remove these images would affect numerous glass related articles on both the english and other language wikipedia's. Or else if someone is an admin on commons and feels like closing then that would also be grand. Polyamorph (talk) 10:04, 9 February 2010 (UTC)

Flux?

The word "flux" does not appear anywhere in the article. I don't know much about the field of glass technology, but I know that any glass worker would say "flux" when talking about the different substances that are added to the melt to reduce its working temperature. —Preceding unsigned comment added by 71.199.121.113 (talk) 20:57, 4 January 2010 (UTC)

I personally don't know much about the manufacture of glass, but I've never heard the term used in such a way. A quick google search hasn't revealed much, except for it's use in stained glass, to facilitate soldering. (In chemistry, a flux is a substance wich aids in the flow of a liquid, but usually doesn't affect its melting point.) I do know that a substance added to induce color is called a dopant. Others watching this article may have a better answer for you, but if you have a source for this information, it would be helpful. Zaereth (talk) 22:42, 4 January 2010 (UTC)

Hmmm... i do remember watching an episode of "how it is made" a few years ago, and the word "flux" does come to mind, but i can't help beyond that SeanBrockest (talk) 00:10, 28 February 2010 (UTC)

This article (at the beginning of the section "The chemical composition of glass") mentions the introduction of a flux to silica in order to lower its melting temperature as it was difficult to obtain the high temperatures required to melt pure silica. Polyamorph (talk) 08:38, 16 March 2010 (UTC)

Adding Links

Why cant I add an external link to Glazette? Its a website only on glass which has lots of members ranging from architects and designers to students. It disburses information on different kinds of glasses and their manufacturing processes. I tried adding it but it keeps getting deleted. —Preceding unsigned comment added by 125.18.16.102 (talk) 05:25, 3 April 2010 (UTC)

Maybe because wikipedia is not a links collection. Materialscientist (talk) 05:34, 3 April 2010 (UTC)

I thought what things are is more important than what they are not. Wikipedia is an information portal. External links are for information which is not on the page. I believe the link is valid. Please clarify. —Preceding unsigned comment added by 125.18.16.102 (talk) 05:51, 3 April 2010 (UTC)

Wikipedia is an interconnected collection of articles, not of loose links to external websites. There are many reasons for that, one being the vast number of information portals. Materialscientist (talk) 06:18, 3 April 2010 (UTC)

I understand your point. Then how do links which read "Substances used in the Making of Colored Glass" and point to www.glassman.com which provides 0 information get included in the list. When we know there are vast no of information portals should the relevance and quality of a site also figure in choosing which links to retain? —Preceding unsigned comment added by Bong.dreamer (talk • contribs) 07:34, 5 April 2010 (UTC)

How - by chance. Cleaned up, thank you. Wikipedia aims at building article content. Indeed, discussions on which external link is more relevant would only divert from that. Materialscientist (talk) 08:11, 5 April 2010 (UTC)

History section

Someone please expand the history section. --Extra999 (Contact ^me + _contribs) 07:43, 21 April 2010 (UTC)

Please remember we're all volunteers. Usually if you see something that can be improved the best thing to do is try and improve it yourself and if you are having difficulties request some help. Anyway, I agree the section could do with some expansion, however there is now a full article on the History of glass so we don't need to go into too much detail. Cheers, Polyamorph (talk) 07:52, 21 April 2010 (UTC)

Optical properties

I report here the comments MaterialScientist wrote on my talk page: "First, thank you for trying to help with articles, but your section on transparency of glass is (i) uncited, (ii) dubious. Amorphization does not change band gap (to the first order), thus transparency is unrelated to that. You imply scattering by polycrystalline material, but this is not a correct comparison - shatter the glass, it will remain glass, but not transparent. Again, transparency is not related to being glass as a state of matter, it is related to the bulk perfection and the band gap. Materialscientist (talk) 07:28, 23 June 2010 (UC)"

And my answer: I was speaking of transparency and clearness, not of non-absorption. A white stone, like snow or a white petal, has a non-absorbing band structure, and yet is not transparent, because it scatters light, without absorbing it. A colored glass absorbs light, and yet is clear, without scattering. And if you grind finely a piece of glass, you have a white material, just like snow, but if you look at the single pieces with a microscope, they are transparent as far as they have dimensions gtreater than the wavelength of light. But to the naked eye, the material is white, and the reason is precisely what I said: the facets of the fragments (or the cell walls and structures, in the case of a white petal) reflect or scatter. Most materials scatter light and are opaque, with or without absorption. So, definitely I do not understand why you are so drastic. If you think i should change some terms, help me (English is not my mother language). But I think I have written substantially correct physics--GianniG46 (talk) 08:04, 23 June 2010 (UTC)

Please take amorphous and single-crystalline SiO₂ and explain with your logic whether and why the amorphous (glass) state is more or less transparent (it is not). We don't see crystalline windows around us so much, which merely reflects the fact that glass is cheaper, but not that is more transparent. Materialscientist (talk) 08:10, 23 June 2010 (UTC)

I think you may have missed Gianni's point here. (Not sure which version of the article text you read, so perhaps the point was not clear when you read it.) He is trying to make the point that many common solids are polycrystalline, and are opaque due to very high scattering rather than (or perhaps in addition to) absorption. I'm not a material scientist, so I can't really judge whether he is correct, but if he is it seems like an important point to include. --Srleffler (talk) 03:00, 25 June 2010 (UTC)

He was trying to make several points, most of which were speculative and are already removed from the article (I haven't read it for some 14 hrs). I actually still don't see a point - most natural inorganic materials are indeed polycrystalline, i.e. neither crystals nor glass. (organic materials are often mixtures.) The success of glass as a window material is entirely due to the technology (of removing impurities and macro-defects in the melt) being old and cheap. This is the only point I see in this story. In short, "what we see around" merely reflects the price of current technology, but not the intrinsic properties or natural abundance of materials. "Glass", as presented in this story, is a cultivated synthetic material; windows are still glass, but transparent materials are already dominated by polymers. Materialscientist (talk) 04:05, 25 June 2010 (UTC)

Hello GianniG46. Thank you for your contributions and your interest in editing the glass article. Please do not take offence when editors revert your revisions, it is merely a process of quality control. Unfortunately your contributions are wholly uncited and therefore are subject to removal at any time by any editor. If you wish to contribute content to wikipedia articles you must ensure that all information is cited using reliable sources, see WP:RS. This is not the place to submit uncited personal essays. Regardless of whether you think your physics is correct or not you must back up everything you submit with a reliable reference. If you need any more information on the rules and procedures for editing wikipedia then WP:Simplified ruleset is a good place to start. Thanks, Polyamorph (talk) 08:27, 23 June 2010 (UTC)

First let me answer to the technical questions: I was speaking of common materials, not of large monocrystals, wihich are exceedigly rare. Of course, a single non absorbing and non-defective crystal is more transparent than a glass (has a smaller Rayleigh scattering). So, if you want, I will add a phrase about single crystals.

For as concerns citations, I will look for them, but I believed the whole matter was not subject to dispute, because I was not speaking of new things, but of known facts. I say it again: edit my terms, if they are linguistically inappropriate.--GianniG46 (talk) 08:40, 23 June 2010 (UTC)

No, it is your responsibility to ensure that the content that you add is accurate (linguistically and scientifically) and cited. Do not expect other users to do this for you. If you wish to create a draft then use a subpage of your userpage (see WP:Subpages but don't create the draft in wikipedia article space. You must not add content to wikipedia that is not cited, regardless of how well known or accurate you think it is. You have to prove this and provide readers with a source for verification. This is the most fundamentally of all wikipedia policies and all users are expected to accept and abide by this. Polyamorph (talk) 10:47, 23 June 2010 (UTC)

Another innacuracy would be the statement that glass is disordered on the molecular level. In fact glasses, and liquids, exhibit a high degree of local structural order. For example, SiO4 tetrahedra are the fundamental building blocks of silica glass exactly the same as in the crystal. This is ordering on the molecular level. There is also a significant degree of structural ordering on intermediate length scales in silica glass from the formation of ring structures. Polyamorph (talk) 11:00, 23 June 2010 (UTC)

Again, this could be only a small formal imperfections. Of course amorphous materials usually have all their bonds (almost all, see the dangling bonds of a-Silicon) and lack only long range order, that is, there is no spatial correlation beyond the first few neighbours. I was speaking of "molecular scale", however, not of "molecules", just to tell the small spatial scale of the scattering centers. Up to now, however, I have not received any substantial criticism to the obvious facts I have exposed. Please, tell me if you think what I have exposed is substantially right or wrong, and explain me why a piece of marble or a snow ball are white and not transparent. --GianniG46 (talk) 11:40, 23 June 2010 (UTC)

If there are factual errors then they will get corrected/removed. The best thing to do is to find sources and write your work according to those sources. You can reference your sources using inline citations, see WP:Citation templates. Polyamorph (talk) 12:44, 23 June 2010 (UTC)

I have some questions about this new addition. First of all, is "opaque" the correct word to use? If my understanding is correct, opaque usually refers to absorption. It seems to me that what is described would be translucence, but I could be wrong. It seems a bit misleading to descibe opacity without going into absorption. This process does not occur in, say, metals, which are usually 100% opaque --even single-crystal metals like the titanium used in fighter jet turbines-- although the new material makes it sound as if it does. Could this be clarified?

Another important aspect, I think, is that not all glasses are transparent at visible wavelengths. Zinc Selenide is a great transmitter at infrared wavelengths, but not so much at the visible. (Although I'm not sure it really qualifies as a glass, but rather, a micro-crystal structure.)

Another question this brings to mind is about "fine crystal." I believe this is just another term for lead-glass, and is not in fact crystal at all, but I find no mention of the rather common term in the article. Is it possible to clear up any confusion this name might cause? Zaereth (talk) 18:23, 24 June 2010 (UTC)

"Opaque" just means that no light gets through the object. A material that scatters very strongly and does not absorb can certainly be opaque, if it is thick enough. A thinner slice of the same material might be translucent. I agree with you that some mention of absorption is probably appropriate, to avoid confusion about opacity due to scattering and opacity due to absorption or specular reflection.

Yes, in common English usage "crystal" can refer to leaded glass, which is not at all crystalline. The term is a misnomer.--Srleffler (talk) 02:49, 25 June 2010 (UTC)

I agree with Zaereth that not all glasses (and certainly not all liquids) are transparent and I have already altered the first sentence to read "...largely to the production of glass compositions that are transparent to visible wavelengths of light". But it should be explicitely stated that many glass compositions do not transmit visible light. Although in some cases they do transmit other frequencies of light, for example, chalcogenide glasses transmit in the infra red,. I also agree with clarifying the other points raised. Polyamorph (talk) 07:58, 25 June 2010 (UTC)

This whole section was very narrowly focused and you should read it "between the lines" (as I did and I still don't understand/accept it). Yes, "glass" there means window glass and "crystal" means (in some instances) lead glass. Materialscientist (talk) 08:19, 25 June 2010 (UTC)

I agree Materialscientist that the section is still rather dubious, despite heavy trimming. I think it is just too much of a generalisation to say on the one hand "this is why crystals don't transmit" and on the other "this is why glasses do transmit" because not all glasses are transmitting and some crystalline materials (even polycrystals) are. Still I think a section on why common window glass is transparent done properly would be a useful addition to the article.Polyamorph (talk) 08:25, 25 June 2010 (UTC)

Thanks for the explanation, Srleffler. I tend to agree that the section could use some improvement. I'm not going to pretend to know exactly how transmission/absorption works on the atomic or molecular level, but diffuse reflection and refraction is pretty straight forward. In my experience, it tends to cause a whitening effect. My concern here is that multiple-boundary reflection/refraction is being used as a sole method for describing opacity, when I am pretty sure that other processes are involved. That, and transmission range are never discussed. Like MaterialScientist said, there are many polymers that transmit in the optical range. There are also many that are completely opaque or translucent in the visual range, but near completely transparent in the IR.

I apologize for adding the confusion about leaded glass, as that had nothing to do with this section, except that something made me think of it. I think there is something about it in another section somewhere, and I was thinking, perhaps we could add some clarification about the misnomer term "crystal" where ever that information is, (I'll have to look for it later). Sorry. Zaereth (talk) 19:06, 25 June 2010 (UTC)

Disambiguation link to eyewear

Currently the article links to eyewear. This is a disambiguation page. Two users have tried to change this wikilink to eyewear (disambiguation). This page does not exist and results in a red link. It is better to link to the actual disambiguation page than a non-existent page. I cannot see any reason whatsoever why we would link to a non-existent page when one already exists on the topic. Actually changing the link from the correct page to the incorrect page constitutes unconstructive editing, regardless of any good faith intentions. The page simply does not exist so stop linking to it! Polyamorph (talk) 07:34, 25 June 2010 (UTC)

Unless you want to make eyewear (disambiguation) a redirect to the actual eyewear disambiguation page I see no justification in changing the wikilink. Regards Polyamorph (talk) 07:47, 25 June 2010 (UTC)

I see no problem with linking directly to the disambiguation page when every link the disamb. page provides is relevant. i did the same thing recently on the moose article with pondweed. I think what Srleffler was trying to do was to hide an indication on the edit screen that would let other editors know not to change it, so they would know it was deliberately piped that way. I think this is probably a good idea as well, and fixing the redlink it creates can easily be solved by creating a redirect back to th disamb. page. Zaereth (talk) 19:23, 25 June 2010 (UTC)

Sorry. I didn't notice that the link was red. I'll fix that with a redirect. See the Guideline at WP:INTDABLINK. One should never intentionally link to a dab page that doesn't have "(disambiguation)" in its title. Deliberate links to such pages are done by linking through a redirect. This tells editors doing disambiguation cleanup that the link is deliberate, so they don't waste time (over and over again) trying to find the correct article to which to link.--Srleffler (talk) 03:15, 26 June 2010 (UTC)

This is fine, thanks for fixing it. Polyamorph (talk) 06:34, 26 June 2010 (UTC)

Semivitreous redirect

Semivitreous redirects to this page, and I'm not certain this makes sense given that glass is fully vitreous and that there's no mention of semivitreous on this page. 71.199.48.77 (talk) 15:19, 31 August 2010 (UTC)

You're right, there should either be a section in this article on semivitreous materials or else the page should not be a redirect. Polyamorph (talk) 18:55, 31 August 2010 (UTC)

From a quick scan of google, it appears that "semivitreous" is a term applied to ceramics, like porcelain or tiles, and has to do with porosity. (ie: The amount of water absorption.) It seems to have nothing to do with glass. Zaereth (talk) 19:08, 31 August 2010 (UTC)

Stoneware mentions semivitreous in its lead. I assumed semi-vitreous would mean a material that is part amorphous, part crystalline. But it may be worth asking on a ceramics talkpage where editors may be more aware of the usage of the term. Polyamorph (talk) 21:07, 31 August 2010 (UTC)

Good idea. I posted a question on Talk:Ceramic. Zaereth (talk) 21:58, 31 August 2010 (UTC)

I took a little time to research this further. It appears from the books Engineering and contracting, Volume 58 and Firing ceramics that certain minerals like china clay or feldspar can be fired at much higher temperatures than typical earthware ceramics, yeilding products like vitreous porcelain. These are useful for making unglazed floor and roof tiles, as well as dinnerware like fine china, since all porosity has been removed and water absorption is practically zero. However, some coloring additives, mainly for reds, browns and blacks, cannot withstand such high temperatures. These are fired at lower temperatures than vitreous ceramics; high enough to eliminate most porosity but not to destroy the color. Semivitreous materials will absorb a tiny amount of water.

Most common dinnerware is semivitreous, because it is much cheaper to make than fine china. Semivitreous plates can be stacked in the kiln, one on top of another. To make vitreous porcelain, the plates must be separated using tools called "Kiln furniture."

Hope that helps. Zaereth (talk) 19:24, 1 September 2010 (UTC)

Ok, for now I'm going to change the redirect to Ceramic as its clear that is more suitable than glass. Cheers Polyamorph (talk) 07:56, 3 September 2010 (UTC)

What a mess

Dear co-authors, to remind you in what a messy state our glass articles currently are, let me just give you one example:

Paragraph 1 currently refers to sugar glass as an example. Paragraph 2 then defines a glass as being inorganic.

Hope you accept this as justifying bold changes. -- Marie Poise (talk) 12:40, 17 October 2010 (UTC)

Yes go ahead and make bold changes where necessary. If you need any help clarifying anything then please ask here. We would all like to see this article improved and so appreciate your efforts to help. Polyamorph (talk) 13:18, 17 October 2010 (UTC)

A passing comment, I'm not sure all the sections under "Silica glass" heading should be there, especially since the composition section refers to network formers other than SiO2. Polyamorph (talk) 13:54, 17 October 2010 (UTC)

Thanks, that needs to be sorted out. -- Marie Poise (talk) 14:41, 17 October 2010 (UTC)

Thanks very much for helping out, it's looking better already! I added some more explanation to the silica section. I also reinstated some of the information in the section "Physics of glass". The content in this section has been agreed on previously through both discussion and mutual editing. The standard definition of glass in a physics sense is one that is formed through bulk melt quenching methods, and we cite this definition using a number of specialist textbooks on the physics of glass (Zallen, Cusack, Elliot etc.) I agree that often this definition is expanded to include all amorphous materials that exhibit a Tg and hence have altered the text to also take this into account. Best regards, Polyamorph (talk) 06:23, 18 October 2010 (UTC)

The section on silica tetrahedra is kind of a strange physics interlude in a chapter that otherwise addresses a rather wide public. I suggest it should be moved to the "physics" chapter, which should start with a section about structure. We also need to emphasize the absence of Bragg peaks. Weren't it so difficult to find public-domain pictures. Hope I can come back to it in a couple of days. -- Marie Poise (talk) 09:03, 18 October 2010 (UTC)

Yes, I agree the structure discussion belongs in the physics section, and agree re:Bragg peaks and the inherent difficulties involved with studying the structure of glasses. If we can't come up with a public-domain picture i'm sure it wouldn't be too difficult for me to produce a suitable image of the S(Q) and G(r) function of Silica and how they relate to 2D structural model already shown in the article (When time permits of course). Polyamorph (talk) 11:07, 18 October 2010 (UTC)

Trademark for glass

Hi I purchased a beautiful glass dish today in a second hand shop it is a face of a beautiful lady, with three flowers in her hair moulded into the base of the dish and there is a signature or trade mark T.Y

does anyone know what this may mean or where I could research further?

thanks Anthony —Preceding unsigned comment added by 94.196.19.197 (talk) 18:51, 23 March 2011 (UTC)

If its a US trademark, the US government has a search engine here - http://www.uspto.gov/trademarks/process/search/ . If it is not, simply google "trademark search" to locate other search engines. Zaereth (talk) 18:58, 23 March 2011 (UTC)

Thanks Zaereth I will check can I email a photo for people to look at?

Anthony —Preceding unsigned comment added by 94.196.19.197 (talk) 19:44, 23 March 2011 (UTC)

I'm sure you could email somebody, but I personally wouldn't be able to help. Others who watch this article may know more, but this page is for making improvements to the article, and not really for discussing topics like this. You might be able to upload it here, but if it's a work of art, then copyright laws may prevent that. (It's all very complicated.) Good luck to you, though. Zaereth (talk) 20:02, 23 March 2011 (UTC)

Pyrex urban legend

I have recently come across the urban legend that Pyrex cookware was borosilicate glass but switched to soda-lime glass when Corning sold the brand to World Kitchen in 1998. Pyrex themselves deny this here: http://www.pyrexware.com/thetruthaboutpyrex/index.htm and Snopes addresses this here: http://www.snopes.com/food/warnings/pyrex.asp I saw in some comments that Pyrex sold in Europe is still borosilicate. (don't have a definite reference for this) My question is, should we mention this in the article or does it not matter enough to rework the section? Thanks. Falconerd (talk) 07:25, 30 April 2011 (UTC)

File:Glass.sculpture.kewgardens.london.arp.jpg Nominated for Deletion

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Proofing of "state" Section

The "state" section of the article needs proofing. There is incorrect grammar. I would have made the changes but I was not allowed to see that section while in "edit" mode. — Preceding unsigned comment added by 173.15.107.1 (talk) 15:31, 5 October 2012 (UTC)

I'd be happy to help, but I don't see any section titled "state" in the article. Can you provide a little more description of what needs to be changed and where? Zaereth (talk) 16:26, 5 October 2012 (UTC)

Oh, I see. It looks like Polyamorph already fixed the problem. Zaereth (talk) 19:30, 5 October 2012 (UTC)

Melting point

I was searching for the "melting point of glass" found this Wikipedia entry about Glass, but I don't appear to be able to find the actual melting point listed? I realise that the melting point will vary for different "alloys" if that's the correct term, thought it might be something useful that can be added. Name of Tony Hine, published on the 7th of August, 2012 — Preceding unsigned comment added by TØnyHine (talk • contribs) 21:14, 7 August 2012‎ (UTC)

The term "alloy" is typically applied only to metals, although metallic glasses do exist. The thing all glasses have in common is that there is no specific melting point. Rather, there is a "melting range," called the glass transition. Typically, the glass will soften as it is heated through this range between solid and a fully melted liquid. For lead glass, full melting usually occurs around 1600 degrees F, which is a glowing cherry-red color. Quartz (Fused silica) has an extremely high melting poiny of around 3000 degrees F (a "crisp your eyeballs" white-hot). Quartz also has a rather narrow glass transition, turning from solid to liquid with very little warning. Zaereth (talk) 05:20, 20 March 2013 (UTC)

From a practical (glassblower's) standpoint, melting is usually deemed to have occurred when the surface tension lowers to the point where welding can readily take place. Zaereth (talk) 18:35, 20 March 2013 (UTC)

Behavior of antique glass

How should this section be reworked since the statement "...once solidified, glass does not flow anymore." is at odds with results found in the paper "Relaxation time and viscosity of fused silica glass at room temperature" by M. Vannonia, A. Sordini, and G. Molesini in the European Journal of Physics E Volume 34, 2011? Dan Watts (talk) 14:48, 12 April 2013 (UTC)

I don't know, so I will have to defer to others, because I do not have access to the full paper. I was able to locate the first two pages, here. From what I have read, there doesn't seem to be any cause attributed to the deformation. What we have here is a detailed analysis of a pair of optical flats that were purchased in 1981, which were rarely used, but were found to be off by a few nanometers in 2008. They equate the deformation to viscous flow, but don't actually say viscous flow is the culprit. In fact, to quote, "Although still on a dubitative ground as to the causes of the observed behaviors, cases of long-term defomation of fused silica plates at room temperature have been reported."

To me, this is an example of why extreme caution should be taken when using primary sources. A good, reliable, secondary source can often provide a much better interpretation. The problems I see with this one (albeit, I haven't read the whole thing ... I think) are: 1) The article reports this as an unexplained deformation. 2) The flats were only tested between 2008 and 2010, during which time there was "no appreciable change." However, during this time, they noticed that there seemed to be a deviation from the original flatness. 3) There is no way to actually know what the true (absolute) flatness originally was, because they were not originally subjected to the three-flat test. They may have been off the whole time, because flatness of the sample flat in an interferometer test is usually relative to the flatness of the test flat 4) This is a very small case study (only two flats, one type of glass, over a two year period, with no change during that time).

I would definitely not try to use this as definitive proof, because it is an admittedly incomplete study. Zaereth (talk) 22:26, 12 April 2013 (UTC)

I appreciate your response, and delving into the references (including one that did observe masurable deviation and is available { http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-18-5-5114 } ) it appears that the first paper is not the best one to use. Perhaps you could also look at this one. Dan Watts (talk) 01:42, 14 April 2013 (UTC)

No problem. This report is similar, except the study is more detailed. This is a study of five flats, of which, only two actually showd any deformation. With one flat, the deformation was rather uniform, similar to the other report's. The other flat showed deformation only in the center, as if the properties of the fused silica varied across the flat. The other three flats showed no deformation during the test period. The report also claims the cause as unknown and, what's more, they have no idea why some flats deform while others do not, and still others only partially deform.

I'm beginning to think this info would best be suited to the fused silica article, but definitely not for antique glass. The optical flat article could definitely use more information. While the report equates the deformation in the fused silica to a viscosity of 10¹⁷ Pa s, it still lists soda-lime glass as being around 10⁴¹ Pa s. Significantly higher.

These studies show that deformation does occur in fused silica in a way that it does not in other glasses. Further more, it also shows that such deformation is not universal, but sporadic, indicating some possible deviation of the material's make-up. When including this info into an article, I would be careful to explain all of this, to state that the deviations are on the order of a few nanometers, and the conclusion is that "no observable effect is ocurring over human lifetime." Zaereth (talk) 17:19, 15 April 2013 (UTC)

Perhaps the conclusion should be "no unaided observable effect is ocurring over human lifetime." They did measure an effect for two flats. Dan Watts (talk) 18:43, 15 April 2013 (UTC)

I can agree with that, and almost added a similar adjectives to the quote, but I would've had to put it in brackets to avoid misquoting. Zaereth (talk) 18:56, 15 April 2013 (UTC)

History

Could we get more-definitive dates in antiquity? and a clearer outline, chronologically, in the History section? Thanks! Now to look for more info about window glass. Misty MH (talk) 08:39, 25 July 2013 (UTC)

English spellings

It appears this article was started using American English in 2001, and then was switched by an IP user in 2006 to British English, for no apparent reason. I will be switching it back as time allows. — Preceding unsigned comment added by 143.65.196.20 (talk) 15:46, 22 August 2014 (UTC)

I've reverted you - we have to keep spelling in references; and if correcting, change spelling all through the article. I'll try to correct this today. Materialscientist (talk) 21:52, 22 August 2014 (UTC)

--Sorry, I attemped to keep them all straight in the refs, must have missed one. Obviously didn't try to convert the references...as it'll lead to dead links

• I was wondering about this. The article should be consistent in its spelling and at the moment it is not. Do any other editors remember a discussion about changing to British English? It appears true that the article was started in American English and was changed in 2006. It has therefore been (predominantly) in this dialect through a longer time and many more edits. Does anyone feel strongly about which way the article should standardise? --John (talk) 23:22, 22 February 2015 (UTC)

Personally, I don't feel strongly one way or the other. I noticed you had changed a couple of words to British spellings, but did not go through the entire article and change them all, so I felt it needed better consistency. I checked the original version of the article, and then checked the entire article as it now exists (using ctrl+F), and it both started and is currently, primarily written in American English. (See the section on color, for example.) Spellings should not be changed within the references, but the text should remain consistent. Zaereth (talk) 23:32, 22 February 2015 (UTC)