Talk:Glass/Archive 2

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Invention of glass blowing

I asked about this on the Reference desk. Some useful information was turned up, it should be merged into the article. The question, and answers, are here: Wikipedia:Reference_desk_archive/Humanities/August_2005#Invention_of_glass_blowing.3F. JesseW, the juggling janitor 04:55, 6 September 2005 (UTC)

Speculation from the "see also" section

An anonymous user wrote:

but it can also be argued that glass formed at different places on the planet can vary in composition or certain subtle variations in composition which lead to differences in viscocity.may be roman and egyptian glasses have a really large viscocity than that of other glass made in the current world. (sic)

In fact, differences in viscosity are most prominent in different types of glass: GeO2 is much thinner than any alloy of SiO2 (no matter where or when it was made), and, as the article mentions, even GeO2 is so viscous at room temperature that the time interval to regard it as a liquid would span 1032 years, which you should compare to the 102 to 4 years that a civilization tends to last.--Joel 17:56, 8 November 2005 (UTC)

Obsidian collection prohibition

The page says: "Obsidian collection is prohibited by law in some places...". This seems unlikely. It has been suggested on Talk:Obsidian that the actual prohibition is of collection of obsidian artifacts. It would be good if somebody could find out for sure and update this page. EdDavies 22:55, 17 November 2005 (UTC)

http://www.colossal-fossil-site.com/475-legislative/36-BLM-regs-state.htm says it varies state to state, i changed it to hopefully make some more sense, why on earth would collecting rocks be illegal?!?

The obsidian cliff in Yellowstone is almost gone now, hauled off in bits and pieces illegally by tourists. Note that rock collecting is illegal in many (if not most) [US] National Parks, along with collecting plants without authorization, etc... Nahaj 04:28, 4 April 2006 (UTC)

Candy glass

N really sure if it belongs here (doubt it), but, anybody care to try explaining how it's made? (If you don't know, it's the stuff Hollywood uses for stunt windows.) Trekphiler 05:30, 9 December 2005 (UTC)

They just melt sugar (probably a special transparent type) and pour it in a mold of the shape they want the glass to be. Then they just wait till it cools.Slartibartfast1992 01:25, 6 December 2006 (UTC)

Glass as a Polymer

Added that section under ingredients. I would like to add some reference to sol gel as well

LaoAn 21:45, 26 December 2005 (UTC)

glass is not a liquid

the little pro/con argument at the bottom of the article is misleading. By investigating the links at the bottom of the page, one can quickly learn that glass is not a liquid, and as such, will not flow. Some glass can be adulterated with minerals to cause it to become softer.

look at the USENET article, Original by Philip Gibbs October 1996.

should not any suggestions that glass is a liquid and flows, be removed? I think so.


Glass is an amorphous solid and will flow beause of the characteristics of this type of solid.Slartibartfast1992 01:26, 6 December 2006 (UTC)

Hydrophillicity and reactiveness

It does not mention in the article, but I believe glass is naturally a hydrophillic material, as the contact angle is small with water. Also glass can be etched by some chemicals like hydrofluoric acid, so it isn't 100% inert... something to note?

An interesting question which I would like to have answered here is why glass is so unreactive. – gpvos (talk) 12:54, 12 March 2006 (UTC)

UV

"Ordinary glass does not allow light at a wavelength of lower than 400 nm, also known as ultraviolet light or UV, to pass."

To my knowledge UV-light can be subdivided like so:

UVA 400 nm - 320 nm UVB 320 nm - 290 nm UVC 290 nm - 100 nm

Of wich UVA passes through windowglass, and UVB and UVC being absorbed (or reflected I don't know). If that's true, then glass is not completely impenetrable by UV light. Any comments?(MrDeBeuker 11:21, 4 February 2006 (UTC))

See this link: [1] virtually all common glasses have this absorption curve of allowing a majority of light above 300nm in the UVA and blocking virtually all light below 300nm. Actually glass blocks partially light between 300nm and 400nm. Mr.K. 03:38, 28 February 2006 (UTC)

"most glass is silicate"

what non-silicate glass is there?


Chalcogenide glass Bridesmill 03:51, 27 May 2006 (UTC)

Fr and De articles

Has anyone else looked at the french and german counterparts to this article? I have to say that both look far better in terms of broad coverage of the science and the history of glass especially wrt to illustrative images. This aricle imho should definitely look to those two for ideas on improvement.--Deglr6328 17:43, 6 May 2006 (UTC)

But *is* glass a liquid? Don't ask wikipedia apparently....

I have no scientific knowledge relavant to any debate over the definition of a liquid or whether glass falls into any such definition. However, it is clear to me as a reader that the article itself coyly avoids answering the question. This is unacceptable. The article should do one of three things: say that glass is not a liquid; that is a liquid (albeit one that is more viscose than the cathedral glass myth would suggest); or that this is something of a 'grey area' and it depends on the definition of 'liquid' adopted. Currently, some statements in the article imply, at least to someone like myself who doesn't already know the answer, that glass is a solid:

  • " One common misconception is that glass is a super-cooled liquid ... "
  • "The result is a loss of focus, and occurs not because the glass is flowing over time..."

Whereas other statements suggest to me that glass might be a liquid:

  • "If medieval glass has flowed perceptibly" - implying that it does flow slightly. If there is no flow at all then this is otiose: it would only be necessary to state that glass does not flow, 'period'.
  • Ditto: "If glass flows at a rate that allows changes to be seen"

And other statements suggest the problem is partly definitional: "he wrote that glass at room temperature is very strongly on the solid side of the spectrum from solids to liquids."

So please - people who know what they are talking about - either come to a consensus on whether the glass is liquid or solid, or, if there are definitional problems, make this clear. The section as it currently stands is very poorly written. --Danward 17:56, 14 May 2006 (UTC)

Try looking here: Glass: Liquid or Solid -- Science vs. an Urban Legend, then write it in yourself. See WP:BOLD --DV8 2XL 19:04, 14 May 2006 (UTC)
Grr - OK, I've had a shot at it. In fact, I've found another well-written source on the subject (which is linked in the new text) which suggests that the whole topic is fiendishly complicated, that there is scope for different views and even that "There is still much about the molecular physics and thermodynamics of glass that is not well understood": [2]. I'd suggest that anyone who wants to attack or improve upon what I've written takes a peek at that paper, because it canvesses a variety of views and aspects of the problem. --Danward 22:24, 14 May 2006 (UTC)

The section is already rather big and quite specific for a general topic. Please consider a summary-style split into a separate Is glass a super-cooled liquid? main article. Femto 11:56, 15 May 2006 (UTC)

That's a fair point actually. I'll look into it when I've got a free moment unless someone else writes it. --Danward 22:26, 16 May 2006 (UTC)

Following the most recent changes to this section (which generally seem to be good improvements), it now states "Glass is most commonly classed as a liquid..." Is there a clear basis for saying that it is *most* commonly so regarded? I would have thought that given this page until recently adopted the line that it was an amorphous solid 'no question', the most one could say would be that glass is "commonly" treated as a liquid (?) --Danward 00:00, 20 May 2006 (UTC)

The reference to pitch clouds the subject considerably. To me 'pitch' isn't a solid by any definition in my head, if someone mentioned it to me I would reference it alongside 'tar' which also isn't a solid. There is no quantified evidence to prove glass has ever flowed once at room temperature under normal conditions. Not a single mention of experiments to deform glass using weights. In conclusion - just because glass doesn't form a perfect rigid lattice structure doesn't mean it isn't a solid (albeit not a solid by 'junior physics' standard, which appears to be the standard used by far too many websites on the web proliferating the myth lacking an understanding of thermodynamics). There are two main websites that deal with the Legend in an adult fashion and both conclude that it is an AMORPHOUS SOLID. they are http://math.ucr.edu/home/baez/physics/General/Glass/glass.html and http://dwb.unl.edu/Teacher/NSF/C01/C01Links/www.ualberta.ca/~bderksen/florin.html and here's the debunking of a person who is clearly teaching junior physics to juniors http://www.newton.dep.anl.gov/askasci/chem99/chem99017.htm (again proliferating the myth - he even says "we all know", but is wrong). http://www.sciencenews.org/pages/sn_arc98/5_30_98/fob3.htm and here again in the American Journal of Physics. Anyone who has read The Science of Discworld books will realise the 'glass as a liquid' is one of those "lies to children" because explaining the truth is far too complicated and would contradict everything you've just said. Any scientist worth his salt would define glass as an amorphous solid, or at least explain that it does not fall within the 'traditional' 2 form boundaries which we created as an easy guide for kids (not for the molecular dissection of every object on earth). - Koncorde --82.42.56.236 14:52, 22 May 2006 (UTC)

Right now the first paragraph says "Clearly, glass is a liquid, since cathedral windows are always much thicker at the bottom." I was under the impression that this was blatantly untrue, and so is a paragraph nearer the bottom of the article. I'd like to at least see the article agree with itself.

History

I'm in the process of editing the history section of this article in my sandbox. More specifically I'm adding new material and tracking down references. Hopefully I will have this completed sometime next week.

Baudoin 19:58, 17 May 2006 (UTC)

The edit is complete and has been uploaded. ````

Thanks

The observation that old windows are often thicker at the bottom than at the top is often offered as supporting evidence for the view that glass flows over a matter of centuries. It is then assumed that the glass was once uniform, but has flowed to its new shape.
The likely source of this belief is that when panes of glass were commonly made by glassblowers, the technique used was to spin molten glass so as to create a round, mostly flat and even plate (the Crown glass process, described above). This plate was then cut to fit a window. The pieces were not, however, absolutely flat; the edges of the disk would be thicker because of centrifugal forces. When actually installed in a window frame, the glass would be placed thicker side down for the sake of stability and visual sparkle. Occasionally such glass has been found thinner side down, as would be caused by carelessness at the time of installation.

I totally learned something new today. much appreciated. -Taco325i 02:55, 20 July 2006 (UTC)

Recurring glass flow stupidity: Here is the standard reference

Some person keeps adding a sentence that glass does not have infinite viscosity. This statement is not true. A solid is per definition definition a system with infinite or very high viscosity (See [glass transition temperature]]).

The following article is a standard refence on flow of glass windows. It is coauthored by following article by Prabhat Gupta who is one of the leading experts in the field. (Sadly it requires subscription)

Edgar D. Zanotto and Prabhat K. Gupta American Journal of Physics -- March 1999 -- Volume 67, Issue 3, pp. 260-262 http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=AJPIAS000067000003000260000001&idtype=cvips&gifs=yes

The article makes use of a model called the Tool_Narayanaswami_model, which is arguably not perfect, but at present this model is the best model that we have.

The point of the article is that window glass does indeed flow, but the flow rate is so slow that it cannot explain the shape of cathedral windows. In other words window glass can be treated as a solid (with infinite viscosity) for all practical purposes. The viscosity of window glass at room temperature is indeeed much higher than pitch.

But when you make this statement you have to be careful to use the right words. The word supercooled liquid is a technical term, and it is routinely applied to systems with a very large viscosity. Over the last few decades a lot of people have tried to model what would happen if we could equilibrate a supercooled liquid far below the glass transition temperature. (See the article about the [Kauzmann_paradox]]). In this context the term super cooled liquid is applied systems with a very high viscosity. In other words the same system can be a supercooled liquid as well as an amorpheus solid.

Glass disease

Any further information for the above appreciated (or merge to this page if appropriate) Jackiespeel 18:40, 27 July 2006 (UTC)

Good Article nomination has failed

The Good article nomination for Glass/Archive 2 has failed, for the following reason:

Lack of citations. Just three? There are lots of statistics that need citing, but what was brought to my attention was the uranium-added glass. More citing, and then it should pass. Iolakana|T 18:10, 28 July 2006 (UTC)
I would decide how you want a spell color/colour. The article tends to flip-flop. Just a suggestion. MJCdetroit 13:43, 15 September 2006 (UTC)
I have changed all text reading colour to color except where calling up an External Link / Reference where I retained the original. I chose the AmE as this is what the original article was written in circa. 2001. Parasite 08:06, 18 September 2006 (UTC)
Um, how many citations does it have currently? i don't know, but it looks like something at least 9. Duinemerwen 02:34, 19 December 2006 (UTC)

More information about types of glass

The article needs more information about laminated glass and various other types of glass. For example, the treated (laminated?) glass used in automobiles, trains and so on (in romanian it's called "geam securizat" direct translation to english: secured glass, I don't know the correct english translation) Persons interested in expanding this may find the following site usefull: http://www.glassonweb.com/glassmanual/index.php Mariushm 19:50, 8 December 2006 (UTC)

Lead content in Glass

Well I heard that glass made with lead generally has 12-25% lead content, depending on how much shine is desired. Anyway, my question here is lets say a glass cup contains 20% lead content, wouldn't that be dangerous to the body and brain to use a cup like that? And will consuming alcohol from a glass cup like this have any effect on the lead? Because I heard some wine bottles stored in lead glass can become contaminated. I'm guessing if lead/glass does get into the body then is probably insignificant and next to nothing, but what about over the course of a lifespan? I don't want to get alzheimer's when I'm older. —The preceding unsigned comment was added by 75.84.4.168 (talk) 03:10, 15 February 2007 (UTC).

Move/Remove the Calculating Glass Properties Section

A section named Calculating Glass Properties has just been added. I think it's way too near the top of the article, if it's even relevant at all.Joelholdsworth 09:12, 16 February 2007 (UTC)

Glass as a container

I was in Australia for a couple of weeks and visited a friend there.

He's working in a glass-bottle factory in Penrith and took us on a tour. (very interesting I might add).

He told us, that glass could contain almost anything. The only substance/liquid it couldn't contain was - and I might have had a problem hearing hip, there was quite noisy in there - Goana Oil. The molecules of that particular oil was simply so small, that the molecules of the glass couldn't contain them, and it would simply flow out of the jar/bottle.

Now, I've never heard of Goana Oil and forgot to ask him further. Can I have misheard him and it's actually something else or?

Is there any other substance glass can't contain?--Nwinther 13:57, 28 February 2007 (UTC)

Hydroflouric acid dissolves glass (albeit slowly), and thus cannot be contained by it for more than a short time. Not the same deal as what you were told, but it's something that glass can't contain. Someguy1221 16:46, 22 March 2007 (UTC)
Refer to Australian humour, particulary An important aspect of Australian English usage, inherited in large part from Britain and Ireland, is the use of deadpan humour, in which a person will make extravagant, outrageous and/or ridiculous statements in a neutral tone, and without explicitly indicating they are joking. BTW, Goanna oil is similar to Snake oil. :) Parasite 23:43, 28 February 2007 (UTC)

Intro section: unsupported or original research?

Quote: > Strangely enough, to make good quality glass, you need to ADD glass to the mixture (or cullet) before it gets to the molten tin furnace to float on. Tin when molten is perfectly flat and glass floats on top as it is lighter than tin, thus giving glass the "float glass" name sometimes used instead of "raw glass".

The whole wording makes me uneasy, but we need supporting evidence first before we talk about cleaning up the wording. As a matter of fact, does the article really need to explain in this much detail how to make glass? —The preceding unsigned comment was added by 204.96.216.30 (talk) 13:13, 1 March 2007 (UTC).

History Section: UFOs?

The discussion of UFOs in the Americas and their connection to glass seems to me rather speculative. It should probably be removed if no reliable source can be found.

MS Excel

"Reduction of the sum of square errors using the Solver option in Microsoft Excel with the glass components as variables" - is Excel uniquely good for this? Otherwise it doesn't seem neutral to mention a specific piece of software.

One Correction Should be Made

In the picture captioned: Hand-blown glass beads and pendants illustrate some of the myriad colors and shapes of glass art. The actual process is lampworked (also known as flameworking), not blown. I have no idea how to go about editing the main page without screwing it up, so someone more knowledgeable should change it. 68.144.87.169 05:14, 30 April 2007 (UTC)

Solid or Liquid?

this is gonna sound retarded to most people. but is glass a solid or a liquid? i assumed it was a solid until my science teacher (he's not one of those insane teachers, he has his facts straight) told me it was actually a super-sedated liquid. i also noticed on the page it said it was "of arguable phase". does that mean they dont know what it is? --Late Leo 20:46, 9 April 2007 (UTC)

Yes glass is a liquid but its flow speed is less than 1mm in about 100 yrs —The preceding unsigned comment was added by 84.250.110.93 (talk) 14:42, 9 May 2007 (UTC).

read the article again you might learn something...glass a does not flow at all there is no evidence of it...the anecdotes of evidence are not proof -- unsigned edit by 24.222.118.137

Glass, as far as I can discern, is an amorphous solid. The idea that it is a liquid is widely believed, since there are many surprising facts in science which refute common belief. Anyone who refutes such a fact can be said to merely speak from ignorance. Consider also the widely-held belief that a duck's quack does not echo. How can the average person expect to refute either this, or the idea that glass is not a liquid? --Jonathan Drain 00:13, 21 August 2007 (UTC)

I've been told by someone who works with laser glass (NIF, specifically) that it's an amorphous solid. The anecdotes about old buildings having thicker glass on the bottom are due to the way glass used to be made, not "flowing." The have found glass put in the other way on accident, so the thick part was on top. 171.71.37.29 19:04, 6 September 2007 (UTC)

Sections deleted

A couple of months ago, with this edit: [3], a big chunk of useful and readable info on glass properties and ingredients was removed and then replaced with the way-too-technical "calculating glass properties" section. The info should really be re-integrated back into the article, and the calculations shunted into some other article. --Bob Mellish 08:15, 15 April 2007 (UTC)

Oh you haven't noticed? no one notices/gives a shit. this happens everywhere all the time. most of the time no one ever notices at all. I'm close to leaving wikipedia due to this ceaseless unchecked vandalism.--Deglr6328 02:55, 4 July 2007 (UTC)
Bob, I recommend that you do so. Any edit that improves the article, I'm all for it. --Jonathan Drain 00:19, 21 August 2007 (UTC)

Proposed WikiProject

So far as I can tell, there does not seem to be an extant project which deals with this article, or several other similar articles. On that basis, I have proposed a project at Wikipedia:WikiProject Council/Proposals#Chemical compounds and mixtures which might deal with subjects such as this. Anyone interested should add their name there so that we can know if such a proposal would receive sufficient interest to at least potentially stay active. Thank you for your attention. John Carter 16:38, 30 April 2007 (UTC)

How is it made?

I came to this article to find out how glass is made, and was surprised that it does not explain the production process, only the composition. I think this would be very useful information to include. Thanks. 134.225.1.162 12:56, 15 May 2007 (UTC)

Archive Created

I've taken the liberty of creating an archive of the old discusssions, as this page was getting a bit lengthy. I don't believe that there were any active discussions in the material that I archived, but if there was, please accept my apologies and feel free to revive it. Thanks! -Sarfa 17:05, 4 August 2007 (UTC)

Non-silica based glasses

Although something does not need silicon dioxide to be a glass, there is very little in this article about non-silica based glasses. Certainly, as what most people think of when 'glass' is mentioned, silica based items should form the bulk of the article, but I was hoping for at least a section covering 'glass' in the more general use. -- 21:32, 27 August 2007 (UTC)

- A section on the properties and uses of various glass compositions has now been revived (not sure why it was ever removed???) This section does however require further editing... Jdrewitt 15:55, 3 September 2007 (UTC)

Overlay glass

I read about the terms "overlay glass" or "cased glass". I believe in German it is Überfangglas http://de.wikipedia.org/wiki/%C3%9Cberfangglas. Would a short definition of these terms fit into the main article? Bernburgerin 19:53, 28 August 2007 (UTC)

Intro Section

The Intro Needs to be changed to a more laymans terms as a person who understands the Theory of Relativity and what not I got lost reading the intro. perhaps move some of the more technical stuff to another heading as i would see it this would be very confusing for someone who doesnt have an understanding of ChemistryYellow Onion 06:05, 6 October 2007 (UTC)

Specifically which bits were confusing? The important thing that should be got across in the introduction is that glass is non-crystalline, it would be good to have a section on glass physics which can incorporate some of the more technical (but fundamental) terms, possibly following the introduction. The physics of glass is an extremely exciting and dynamic field as the structure of glass and the physics of the glass forming process is still yet to be resolved.Jdrewitt 13:55, 6 October 2007 (UTC)