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Finding the Viscosity of Pitch
ColdChrist writes "The University of Queensland has a page about a 72-year-old experiment on the fluidity of pitch. There's a webcam where you can try to become the first person ever to see a drop of the pitch fall; eight drops have fallen since 1930 and the ninth is now forming. The experiment 'demonstrates the fluidity and high viscosity of pitch, a derivative of tar once used for waterproofing boats. At room temperature pitch feels solid - even brittle - and can easily be shattered with a blow from a hammer', but it does flow, as the pictures demonstrate." I know this is going to bring up glass comparisons, so we'll head those off: glass is not a fluid.
never dribbles
This would look excellent with a time-lapse movie. It can't be too hard to generate MPEGs automativally and have the latest available for download.
Any commend line JPG -> MPG converters out there???
Offtopic, Inflammatory, Inappropriate, Illegal, or Offensive comments might be moderated up.
Yeah right. Sounds just as exciting a pastime as watching paint dry.
The experiment is sitting in a glass cabinet just outside one of the lecture theatres used for a lot of first and second year engineering and science lectures.
When I started in first year (1999), the pitch had formed into an interesting drop, and it provided students with a pretty geeky talking point while waiting for lectures to start.
I remember when we went for holidays one year, and came back to find that the drop had fallen! Everyone was a bit pissed (understandably) that it had fallen during uni hols.
Apparently the rate of drop formation is slowing down due to the air conditioning in the building. Or at least thats a rumour circulating around UQ.
This reminds me more of the T1000.
Well, from that very link one can glean: 'There is no clear answer to the question "Is glass solid or liquid?".'. Of course, that does not absolutely preclude the possible truth of michael's assertion, but it does make it seem a little ambigous. Oh, the semantics!
Money for nothing, pix for free
Ya know, ppl sitting around eating pizza waiting for this to happen is how they get too fat to work for the FBI! ;-)
I can't see it on the movie! Maybe that is because the movieserver is slashdotted.
Sig (appended to the end of comments I post, 54 chars)
Lord Kelvin (William Thomson) created an older pitch experiment: one which had a variety of objects lying on a tray of pitch that are slowly sinking in.
Its usually on show in either the Hunterian Museum or the Department of Physics and Astronomy at Glasgow University.
As I recall, this is considered the oldest continuously running scientific experiment, with the exception only of a wheat-breeding experiment in England? (I can't find references on that, just remember it from back in the mists of time)
BTW: it is more fun to watch paint dry - its faster...
Right now.
In reality we are able to work on discovering the cure for cancer, colonizing Mars, developing Anti-gravity devices and all sorts of other things.
Now, in a strategy game, if all we did was focus on learning the viscosity of pitch, I would have to be pissed at the (l)user that was directing us to do that...
-.-
If you ignore the other uses of a tool, does that make the tool less useful, or you less useful?
It is pitch black. You are likely to be eaten by a grue.
Next, someone will tell us how a friend of a friend woke up in a bathtub full of ice...
Reminds me of a cornstarch and water experiment we used to do. Mix it together and you get a weird substance that exhibits properties of solids and liquids. Try it if you're bored...
According to the website "that now, 72 years later, the eighth drop is only just about to fall.", it seems 7 drops have fallen so far and the 8th not the 9th drop is now forming. Although this seems like a minor detail, it's a 12% difference in the number of drops, which given that pitch has a computed viscosity of over 100 billion times that of water, 12% could add up to a lot.
-This sig intentionally left blank
but it does flow
Oh, so it's like glass then.
What?
.sig last updated Jan. 14, 2000
They should test the viscosity of Waffle House waffle batter! That's some thick 5hit. Of course it hasn't been proved to be a liquid either. I think DuPont did most of the research for it. Maybe we could ask them.
Considering that the 8th drop fell in Nov. 2000 and the one before that dropped in 1988, we have only spent the first two years. I would expect that it would take at least 5 years before the next one drops. It will require more thant the students there to keep us entertained for that much time.
wait, and wait, and wait.. Oh, and wait some more. After waiting, we wait some more...
Sounds like fun...
At least you can bet against the pitch drop... Bonzi!
Tournament Management Online &
Sorry, but I just couldn't resist the pun...
Must be a slow news day.
Yeah, I haven't slept in 32 hours. That's funny to me.
--
http://nemilar.net - Not your grandmother's soup kitchen
...who when reading the article - and looking at the picture of the smashed pitch - finds it hard to get images of a slow motion T-1000 out of my head?
Your objection is just semantics. Didn't you read the article? Michael obviously meant to say that glass doesn't flow.
I'd consider the universe to be the oldest experiment that I know of, or is it just a very elaborate joke?
I tried it.. and server has reached max capacity!.. So I guess many do not share your opinion.
It depends in what way you look at it, to a physics chap this may be one of the most beautiful things he's ever seen, while to a coder it may be damn damn slow and boring.
My Aurora : http://www.youtube.com/watch?v=o91ZsGwJYyg
FB : https://www.facebook.com/TanveersPhotography
Michael,
Please read the articles you link to. In particular, note the "Conclusion" section. Quote: There is no clear answer to the question "Is glass solid or liquid?".
I mean, you should know better than to post such blatant trolls.
www.timcoleman.com is a total waste of your time. Never go there.
Mmmmm....waffle house. The only good thing I ever found in Huntsville Alabama
"I know this is going to bring up glass comparisons, so we'll head those off: glass is not a fluid."
:) From the article:
.... sheesh. ;)
Did the editor not read his link?
Conclusion
There is no clear answer to the question "Is glass solid or liquid?".
And folks complain about us posters not reading articles
the state of matter (liquid vs solid) is highly subjective to the timeframe in which you view it. as a chemical engineer i tend to see glass as a liquid in a technical sense, but as a solid for practical consideration. i too find it hard to see how michael could come to his conclusion from the link he pointed out. perhaps this was a poor attempt at sarcasm.
fwiw i've met people whos research focuses on the liquid properties of glass. it would be nice to see michael in an academic discussion with them.
-- john
In reality God is a hacker who rooted the Universe.
So yes, it's a big experiment (read: Honeypot project)
Has anyone tried something like this with a quicker (but not too quick) fluid?
This would make an excellent Calendar type device - a glass funnel full of SOMETHING (my rubber bible is at home - anyone got one handy???) that would drip through in about a year.
Great for lecturing opportunities when people say 'what the fuck is THAT' and point at your bell jar full of brown gooey stuff!
But glass does flow; the windows in my house (built in 1912) are already showing droop towards the bottom of the frames. Anyone that has ever been in an old house knows that glass flows over time.
During an underground exploration, a few friends and I also came across this phenomenon. I don't remember if we saw any on the ground, but here's a very dripping piece.
What ever happened to basic chemistry class, folks? Glass is known as an amorphic solid, a solid with no crystal structure.
b er2000/ posts/157145.shtm
Here's a good link:
http://www2.abc.net.au/science/k2/stn/octo
Bel, the mostly sane.. "Of course I can't see anything! I'm standing on the shoulders of idiots." -- Me
I suppose he should be thankful that it wasn't the other trough associated with drinking large quantities of beer...
is a federal judge deciding what to do about the Msft case.
try { do() || do_not(); } catch (JediException err) { yoda(err); }
If you would read the materials on the subject, they say that older glass is thinker at the bottom because older methods of producing glass did not produce uniform sheets in the first place, and they were put into the window frame with the larger side down to reduce rattling, back in 1912 when the house was built.
I've had enough abrasive sigs. Kittens are cute and fuzzy.
I have heard that cheeses made in the middle ages have developed thicker rinds at the bottom over time due to very slow cheese flow, but I have never seen it firsthand. Does anyone know if cheese is a liquid or not?
It's also strange to pur it onto a table - itpours out of the glass like treacle would, but then it breaks on contact with the table. Then, it liquifies again, very reminiscent of Terminator, when the shattered metal melts.
Please explain.
I have a page about telescope making that should give you some jumping off points, but I haven't yet got to the polishing stage of the mirror I'm working on.
One reason for using pitch is that you can press a mirror into it and get a very close fit. Another is that if the mirror is not perfectly spherical, the pitch will flex as the mirror moves across it. And finally, the polishing abrasive (ferrous oxide or cerium oxide) will set in the pitch and have a planing action rather than rolling around and chipping little flakes off as in ordinary grinding.
Pitch is nasty stuff to work with. It takes a lot of practice before a novice telescope maker can make a pitch lap they're happy with.
-- Could you use my software consulting serv
The whole "glass is a liquid" thing is a classic example of one of thos things that people say without really understanding understanding what they mean. This article, which is well written, addresses the two main points that you need to prove that glass isn't a "liquid".
It then refutes the common and to my knowledge ONLY evidence for glass "flowing" on human timescales, the thickness difference in the top and bottom of old windowglass. Windows that are OPPOSITE what one would expect to find and the fact that hanging the windows with the thick edge down was common practice neatly debunks this evidence.
So, READ the whole article before you quote without understanding context...
+++ ATH0 +++
Now THAT's how I like my coffee...
In fact, another page confirms that the 8th drop fell in November 2000, so it is indeed the 9th drop forming.
Patrick Doyle
I mod down every jackass who puts his moderation policy in his sig. Oh, wait a sec....
Robert H. Brill, Research Scientist
The Corning Museum of Glass
July, 2000
Early one spring morning in 1946, Clarence Hoke was holding forth in his chemistry class at West Side High School in Newark, New Jersey.
"Glass is actually a liquid." the North Carolina native told us in his soft Southern tones. "You can tell that from the stained glass windows in old cathedrals in Europe. The glass is thicker on the bottom than it is on the top."
Now, more than half a century later, that is the only thing I can actually remember being taught in high school chemistry. I didn't really believe it then, and I don't believe it now.
In the years that followed, I came across the same story every now and then. Most often it popped up in college textbooks on general chemistry. And now, thanks to the Internet, our Museum has received dozens of inquiries about whether or not this is true. Most people seem to want to believe it.
***
It is easy to understand why the myth persists. It does have a certain appeal. Glass and the glassy state are often described by noting their similarities with liquids. So good teachers, such as Mr. Hoke was, like to quote the story about the windows. As is the case with liquids, the atoms making up a glass are not arranged in any regular order-and that is where the analogy arises. Liquids flow because there are no strong forces holding their molecules together. Their molecules can move freely past one another, so that liquids can be poured, splashed around, and spilled. But, unlike the molecules in conventional liquids, the atoms in glasses are all held together tightly by strong chemical bonds. It is as if the glass were one giant molecule. This makes glasses rigid so they cannot flow at room temperatures. Thus, the analogy fails in the case of fluidity and flow.
***
There are at least four or five reasons why the myth doesn't make sense.
Some years ago, I heard a remark attributed to Egon Orowan of the Massachusetts Institute of Technology. Orowan had quipped that there might, indeed, be some truth to the story about glass flowing. Half of the pieces in a window arc thicker at the bottom, he said, but, he added quickly, the other half are thicker at the top. My own experience has been that for earlier windows especially, there is sometimes a pronounced variation in thickness over a distance of an inch or two on individual
fragments. That squares with the experience of conservators and curators who have handled hundreds of panels. Although the individual pieces of glass in a window may be uneven in thickness, and noticeably wavy, these effects result simply from the way the glasses were made. Presumably, that would have been by some precursor or variant of the crown or cylinder methods.
One also wonders why this alleged thickening is confined to the glass in cathedral windows. Why don't we find that Egyptian cored vessels or Hellenistic and Roman bowls have sagged and become misshapen after lying for centuries in tombs or in the ground? Those glasses are 1,000-2,500 years older than the cathedral windows.
Speaking of time, just how long should it take theoretically-for windows to thicken to any observable extent? Many years ago, Dr. Chuck Kurkjian told me that an acquaintance of his had estimated how fast-actually, how slowly-glasses would flow. The calculation showed that if a plate of glass a meter tall and a centimeter thick was placed in an upright position at room temperature, the time required for the glass to flow down so as to thicken 10 angstrom units at the bottom (a change the size of only a few atoms) would theoretically be about the same as the age of the universe: close to ten billion years. Similar calculations, made more recently, lead to similar conclusions. But such computations are perhaps only fanciful It is questionable that the equations used to calculate rates of flow are really applicable to the situation at hand.
***
This brings us to the subject of viscosity. The viscosity of a liquid is a measure of its resistance to flow-the opposite of fluidity, Viscosities are expressed in units called poises. At room temperature, the viscosity of water, which flows readily, is about 0.01 poise. Molasses has a viscosity of about 500 poises and flows like... molasses. A piece of once proud Brie, left out on the table after all the guests have departed, may be found to have flowed out of its rind into a rounded mass. In this sad state, its viscosity, as a guess, would be about 500,000 poises.
In the world of viscosity, things can get rather sticky. At elevated temperatures, the viscosities of glasses can be measured, and much practical use is made of such measurements. Upon removal from a furnace, ordinary glasses have a consistency that changes gradually from that of a thick house paint to that of putty, and then to that of saltwater taffy being pulled on one of those machines you see on a boardwalk. To have a taffy-like viscosity, the glass would still have to be very hot and would probably glow with a dull red color.
At somewhat cooler temperatures, pieces of glass will still sag slowly under their own weight, and if they have sharp edges, those will become rounded. So, too, will bubbles trapped in the glass slowly turn to spheres because of surface tension. All this happens when the viscosity is on the order of 50,000,000 poises, and the glasses are near what we call their softening points.
Below those temperatures, glasses have pretty well set up, and by the time they have cooled to room temperature, they have, of course, become rigid. Estimates of the viscosity of glasses at room temperature run as high as 10 to the 20th power Scientists and engineers may argue about the exact value of that number, but it is doubtful that there is any real physical significance to a viscosity as great as that anyway. As for cathedral windows, it is hard to believe that anything that viscous is going to flow at all.
It is worth noting, too, that at room temperature the viscosity of metallic lead has been estimated to be about 10 to the11th power, poises, that is, perhaps a billion times less viscous-or a billion times more fluid, if you prefer than glass. Presumably, then, the lead caming that holds stained glass pieces in place should have flowed a billion times more readily than the glass. While lead caming often bends and buckles under the enormous architectural stresses imposed on it, one never hears that the lead has flowed like a liquid.
***
When all is said and done, the story about stained glass windows flowing-just because glasses have certain liquid-like characteristics-is an appealing notion, but in reality it just isn't so.
Thinking back, I do recall another memorable remark by Mr. Hoke. One day, our self-appointed class clown sat senselessly pounding a book on his desk at the back of the room. "Great day in the mawnin', son! " shouted Hoke. "Stop slammin' your book on the desk. Use your head!" That was good advice-no matter how you read it.
Reprinted with permission from Dr. Robert Brill, brillrh@cmog.org
I swear to god I saw a link to this site like 2 years ago in a round of Quickies. However, I'm sure the timeframe is such that the statute of re-posted links has run out. Damn the /. search page for not helping to prove me right!...
Sometimes I doubt your commitment to Sparkle Motion.
And it's more fun to play with than pitch.
No Zen is good zen
It's 8:50a EST. And, it finally dropped!
idm owns me
...we've guaranteed that noone will see the pitch drop. At least not until this goes "under the fold."
sarchasm: The gulf between the author of sarcastic wit and the person who doesn't get it.
instead of colonizing Mars [...], let's see how viscous pitch is! Yeah, great idea. Geez.
Low-viscosity substances may be very useful during space exploration.
For example, a low-viscosity substance may be more efficatious than a flexible solid gasket when sealing the joint between a window and a bulkhead.
The only way to know this is to experiment with low-viscosity substances.
The experience gained by determining the viscosity of pitch should not be dismissed out-of-hand.
Who knows, pitch itself may be just the right substance!
Those who sacrifice security to condemn liberty deserve to repeat history or something. - Benjamin Santayana
You have to order a pint 2000 years in advance. :^)
As a UQ student, I'm lucky enough to see it once a week. Since its last drop, there's now a big long tail from the drop to the funnel. I imagine that, just like before a drop, the physics staff and students will gather round and place bets on when they think it'll break off. Apparently there is a fair bit of money in it...
/.ed will probably land me (or somebody else) in a great deal of trouble. And of course, no visit to UQ is complete without a visit to kewn.
And this is just one example of how our Federal Government's massive spending cutbacks on higher education, and the consequent reduction in spending on research, can produce breakthroughs in science. But of course, our biggest breakthrough is our Scramjet program -- NASA's hundreds of millions of dollar and hundreds of brilliant scientists and engineers, we did for A$1.5 million (that's about US$7.84), a couple of basements full of shock-tunnels, some second-hand rockets, and a handful post-grad students.
Finally, seeing as everybody enjoys looking at UQ web cams so much, you can also view FoyerCam, an incentive to make us messy students keep out foyer clean in our computer science building. There's more cams here, but having 2 servers
But maybe it's a liquid . . .
There is no clear answer to the question "Is glass solid or liquid?". In terms of molecular dynamics and thermodynamics it is possible to justify various different views that it is a highly viscous liquid, an amorphous solid, or simply that glass is another state of matter which is neither liquid nor solid.
From the page linked at the end of the posting.
I did read the whole article. I also studied the subject for a while when doing a physics degree at university so I am keenly aware of the context.
Michael was flat out wrong in that the article explained the debate, and the rather than supported one side of it. It is, as the article said, a matter of semantics.
Liquid means lots of things: the two most common technical meanings are 1) this flows and 2) this has no long range crystalline order. Hence by 2) glass is a liquid, and by 1) glass isn't. Hence the conclusion from the article that it is a matter of semantics.
Hope the FPS are high enough on the web cam. Otherwise you'll be looking at it and still miss it.
So nothing in the pitch breaks down to form a droplet of other stuff instead of pitch? It sure sits there for long enough.
As a glass scientist, I wanted to add my 2 cents worth. Almost any substance can occur in a glassy state if quenched fast enough. This includes most metals, plastics, and pitch. Below a critical temperature (the glass transition temperature Tg) a glass is a brittle, perfectly Newtonian solid. At temperatures above Tg, viscosity decreases to the point where relaxation can occur, and the substance becomes rubbery, then fluid. The apparent viscosity at Tg is ~ 10^13 poise. Real motion is observed at ~10^8 poise. The Tg of optical pitch is a bit below room temperature, and the room temperature viscosity is ~10^9 poise. The problem with the experiment cited is that temperature fluctuations change the viscosity exponentially. Droplet formation time will vary accordingly.
Wow, that's exciting. Except that I didn't see it actually drop. But I looked at the video and it certainly seems like it has dropped. Wow, I can't wait to see the real-time/slow motion replay.
THIS SPACE FOR RENT
as well be me, you Karma Bogarts.
Pee-atch!
'sup, fo'?
If Slashdot were chemistry it would look like this:Cadaverine
That is an example of a non-Newtonian fluid. Normal Newtonian fluids' viscosity is a function of temperature: the colder it gets, the thicker it gets. Non-Newtonian fluids' viscosity is a function of something else, in this case, force. That is, the more force you apply to it, the thicker it gets. If you want a really good and simple 'goop' recipe, try this:
-white glue, mixed with water, 50:50
-tablespoon of borax (from laundry section) in a few cups of water
-(optional) food coloring mixed with glue
pour the glue/water mix into the borax solution and it with thicken up. You'll pull out a slimy, goopy mass that is too watery to play nicely with but if you work it in your hands for a bit to get the excess water out, you'll have some fun. Bounce it around, slap it, tear it and it's more like a solid. Let it sit on your hand and it flows like a liquid. Plenty of fun.
In Soviet Russia, hot grits put YOU down THEIR pants.
I don't see any reference to it at real.com. Has anyone been able to play these clips under Linux? When I try it with RealPlayer 8 (which btw is not very easily found at real.com), I just get "PNR_SERVER_ALERT".
How exactly is a fluid different from a liquid?
Woo Hoo!
I remember this one from freshman chemistry.
Fluids flow, man.
Fluids are liquids *and* gases.
The major macro-difference between liquids and gases is that gases are compressible.
cant they just position some sort of beam afew mm below the drop, when it gets close to dripping point wont it slowy speed up as the stem stretches and gets weak? - the beam would be placed at the right point and lowered a bit every day so that when it breaks the beam you get an advanced warning in time to get out of bed and run down the road in your underwear so you could see it.
Or, you could use a zoomed in, high-res video camera connected to a computer that could analyse the the speed constantly and give out warnings as required.
This comment does not represent the views or opinions of the user.
This needs some serious modding up. It's not like the scientists at Corning are playing around. Glass is their life.
At any rate, I just read this article yesterday, in fact. In my other life outside of real work, I'm a glass artist - I work mainly in stained glass ("cold" work, solid enough if you're trying to score and snap!) glass fusing ("warm" glass) and beadmaking or lampwork (at the very edge of "hot.") The properties of my meduim are fascinating to me.
One point that the above quoted article brings up is the "viscosity" or flow-ability (for lack of a better way of putting it) of the lead that is used in stained glass work. Buh-leeve me, the lead is far more pliable and - dare I say it? - "fluid" than the glass. So is the lead/tin solder used in another method of glass work, copper foil.
At any rate, the Corning Museum of Glass has a web site that's good for all sorts of glass surfing.
Consigned to flames of woe.
Perhaps, but that doesn't explain why they claim there had been only 7 drops.
Patrick Doyle
I mod down every jackass who puts his moderation policy in his sig. Oh, wait a sec....
What?!? They're calling this news? I heard about this 10 years ago!
(This is a joke, folks. Sheesh.)
By your definition, sand is a liquid which it is clearly not. You can not use the property of viscosity alone as an indicator of whether something is a liquid or not. freshman chemistry doesn't teach you all the things you know. i would know because I'm taking honours chemistry 3rd year. The stuff you learn in first year chem is just enough to get the other science students familiar with the material.
Whoever built this thing should have made it taller, much taller, say, 10 feet. Also, it should have been made with enough pitch to last 500 years. That would have been cool. As it is, the last drop of pitch didn't even completely fall. Soon there will be no more drops, just a continuous flow of pitch, because the setup is too short. Also, look at the container at the bottom. Can it hold all the pitch that is coming its way? I doubt it. Sooner of later this is going to make a big sticky mess.
Lasers Controlled Games!
I rememebr this, it used to sit at the front of the old Kelvin Lecture theater before the remodelled it, in fact it sat out in the open and it was pretty much gathering dust.
It was more like a little series of steps, pitch had been placed in a reservoir at one end and had flowed down the steps into the reservoir at the other end. In fact it had started overflowing at the bottom.
In Mediaeval times panes of glass were often made by the Crown glass process.
Since I live in the US and went to a junior high school that was slightly over a whole century old I saw panes of glass in this building that were thicker at the bottom that they where at the top, and glass appeared to have ripples in it, and it was not manufactured that way. I know it wasn't medieval glass as the US hasnt had a dark ages, er... well at least before now.
If you ever pull an old window out of a house, take a measurement of the top and bottom portions of the glass pane. You will notice that the bottom of the glass is thicker than the top.
Conclusion: Glass will flow download, but the motion is imperceptible and extremely slow, not noticable except over a long period of time. This may not apply to all varieties of glass however, but the old glass panes are definately thicker on the bottom (and we not when installed).
So does asphalt.
Check out the pavement at most any bus stop.
In profile, the location where the bus's tires are most frequently becomes a valley, with two soft ridges rising on either side.
As transient as the weight of the bus is, for a given moment at a single point, the cumulative effect is more than enough to displace the pavement into a trough.
Valley-to-crest dimensions can reach several inches in total depth.
Cool, huh?
t_t_b
I'm on PJ's "enemies" list! Are you?
www.thinkgeek.com is reselling a goo they labeled "smart mass." The original product is Crazy Aaron's Thinking Putty. I'll leave it to google to provide links. Crazy Aaron has quite a few mpeg's of the product being shot from a potato gun.
It's similar to your cornstarch putty, though a bit more involved. It exhibits different properties on four different time scales. It will drip on its own weight slowly, will bounce firmly if dropped, will tear and shear if pulled too quickly, and will shatter if struck with a hammer.
Kinda like the force shields in the Dune movie and books. You can dent it easily with a fingertip if you move slowly, but it will repell your fist if you try to punch it.
[
I would rather know the pitch of viscosity - is it middle-C, or something else?
www.eFax.com are spammers
From the last paragraph:
Just goes to show you that you can't argue experimental evidence with logic. I wish I would have met you in a group of people, had you calmly point your astounding piece of logic out ot me, so I could have pointed out how pretentious and silly you were arguing that somthing very verifiable didn't exist, because it didn't make sense.
:-)
Boy, you must be real fun to have lunch with
Table-ized A.I.
This may not apply to all varieties of glass however, but the old glass panes are definately thicker on the bottom (and we not when installed).
Even a *small* amount of "flow" would ruin telescope optics over say decades. If true, then my little ol' 60mm may grow nearly useless soon.
I hope those who chewed you out for not reading the slashdotted article are right and that the lenses won't warp.
Table-ized A.I.
It would just look like any other fluid dripping out of something over time-lapse.
autopr0n is like, down and stuff.
Oddly enough the article you cite to claim that glass is not liquid makes no such assertion. And in fact concludes that glass may be thought of as a highly viscous liquid as there is not a 4th state of matter somewhere betweeen solid and liquid. Glass does not exhibit the crystaline structure which is usually a definitive characteristic of a solid.
"but the old glass panes are definately thicker on the bottom (and we not when installed)."
You know this? That the glass was NOT thicker at the bottom when it was installed? You were there those many years ago?
Two anecdotes. One - my own house. Built in 1917. The window glass is wavy - probably made from blown, cut cylinders of glass that were heated into sheets, a manufacturing process that was thick (heh) with inconsistencies. (Modern day glass is floated on molten tin - thus the name "float glass." Another, older process is to spin a glob of molten glass into a sheet, cool it and cut it down. The glass towards the center of the glob would have been much thicker and probably installed at the bottom of the pane.)
The glass in my house is not thicker at the bottom, necessarily. Some panes are, some are not. Some are thick right in the middle, some are wavy, some have bubbles. This is due to the manufacturing process at the time. Or maybe glass just doesn't start "flowing" until - ding! - exactly 100 years! I have to wait another 14 years then it'll suddenly appear.
Second - I "do" stained glass. Clear "antique" (wavy glass still manufactured using one of the above older methods) is still easy to buy, but why buy when you can get it free? I know someone in the home re-hab biz who gives me old window panes. Some are >100 years old.
I just cut out a half dozen of those >100 year old panes from their frames. I scored them, ran the score by tapping the glass with the brass end of my cutter, and "popped" out the pane. None of the glass was noticably thicker at one spot than at another - at least not thicker than what was produced by the manufacturing process of the day. And I'd have noticed. I was removing the glass without benefit of power tools...just the old fashioned score and run method.
Sorry, the glass flowing to the bottom of the pane business is just urban legend. There are people whose entire careers are built around antique stained glass restoration who've not seen anything more than manufacturing "defects" in glass.
And to paraphrase the Corning article mentioned upthread: If all these old window panes "flowed" so much, why aren't glass vessels from ancient Rome and Egypt just unrecognizable blobs by now? They're much older than some cathedral windows.
Consigned to flames of woe.
I read the article. Did you read this part
In fact, optical glass is usually not the same as the glass used in windows and bottles... So old telescope lenses and mirrors provide good evidence that some glasses do not flow, but little evidence to support the claim that glass in old windows has not flowed
You may chew, but I'll bite back - phorm
So, not content with making people look at the scientific equivalent of paint drying, you've decided to Slashdot every "flass glows" website on the planet! <g>
The glass was thicker at the bottom when it was made. Usualy it was put big-side-down, but occasionaly you will find window panels where the larger part is on the top.
autopr0n is like, down and stuff.
I had no idea that micrometer's were able to see into the past! I thought they just mesured length!
autopr0n is like, down and stuff.
Maybe he meant that even though it was a liquid, it was a not a fluid. The articaly clearly states that it is not a fluid (it will not move to fill it's container), although it may be considered a liquid.
autopr0n is like, down and stuff.
It's not possible:
The glass transition is purely kinetic: i.e. the disordered glassy state does not have enough kinetic energy to overcome the potential energy barriers required for movement of the molecules past one another. The molecules of the glass take on a fixed but disordered arrangement.
Your windows are in the exact same shape they were when they were made.
autopr0n is like, down and stuff.
My experience came mostly from quite old windows being changed in quite old houses (circa early 90's, late 80's). Guess these were probably "crown" glass, installed to an antiquated standard.
Once again, it's nice to be disproven with somebody with better experience and/or a grounded opinion. Much nicer than "you're wrong, you suck." Or "read the article, I read 50%, but you still suck".
To be well-beaten by a gentleman is much more pleasing than to be ill-cursed by a cur - phorm
hard yet fluid black
no eyes has seen it falling
time denies the Way
"To be well-beaten by a gentleman is much more pleasing than to be ill-cursed by a cur - phorm"
;-)
Thank you...for the "gentleman" part. But...and lets just keep this between you and me...I'm a girl!
Hey, maybe *that's* why I'm so dang nice...
Consigned to flames of woe.
"Glass is not a fluid"
And
"glass may be a liquid"
Are not incompatable statements, as 'fluid' is not the same thing as 'liquid'
The artical clearly states that glass will not flow, so it is clearly not a fluid.
autopr0n is like, down and stuff.
> In terms of molecular dynamics and thermodynamics it is possible to justify various different views that [glass] is a highly viscous liquid, an amorphous solid, or simply that glass is another state of matter which is neither liquid nor solid.
Thus it seems best to call it a "solid liquid" as this phrase emphasizes the antagonistic properties of glass.
He saw some dirty arabs and fired. Too bad it was just some friendly kurds, BBC reporters and his fellow cowboys.
I remember the pitch glacier too, and I guess it was undustable (a 100-year-old layer of dust having just sunk into its surface). However there was a different experiment /as well/ - which had thinks like corks and metal weights lying in it. The pitch glacier was (I guess) meant to amuse the students, whereas the other one actually was an experiment.
:( during the installation of the new floor for the Astronomy dept, most of Kelvins things either went to the Hunterian or into a skip (I kid you not).
I'm not sure you'd have seen this one, at the time you'd have been passing through (I checked yer homepage) the Kelvin Museum on the 4th floor was also the lecturer/postgrad coffee room and pretty much out of bounds to undergrads.
When the room was found to be riddled with asbestos
-Baz (PhD, Nuclear Theory, Glasgow 1990-94)
"I dunno what would happen if you took a block of glass @ 1000 degrees and then hit it with a sledgehammer. I'll have to try it next time I'm in the studio; I suspect the hammer will just bounce off."
I love it! In what other "hobby" (and this ain't crafting duckies out of doilies, here) can you heat something up to 1000F and whack it with a sledgehammer just to see what happens!?
What if the sledge gets stuck in the glass? It might, I've had a small raking tool get pretty bogged down in >900F glass. Have a bucket of water handy.
I do wonder just how hot you'd have to get glass to have it flow in a more water-like manner.
Consigned to flames of woe.
Still, it moves.
If you want to see it on the webcam, you have to give Real.com your credit card number in order to download the real player!
-- Fuck Beta
Actually, the effective viscosity of a non-Newtonian fluid goes down as you apply more stress to the material. So in other words, the more force you apply, the weaker it gets. Non-Newtonian, like Newtonian, viscosity also depsnds on temperature.
Also, the property that the cornstarch and water recipe and the pitch experiment demonstrate is not non-Newtonian viscosity but viscoelasticity. A viscoelastic material behaves in different ways depending on what type of viscoelasticity it has, but the simplest case is Maxwell viscoelasticity. On short time scales the material behaves elastically (can be shattered with a hammer, bounced off the floor, etc.) and on long time scales it behaves viscously (will flow out of a funnel).
By your definition, sand is a liquid which it is clearly not.
I think you're responding to the wrong comment.
I didn't define liquid at all. I defined a fluid as a liquid or a gas, which I believe is accurate at least at the lay level.
I never even mentioned sand, nor would it fit my definition of fluid as sand is solid.
And if you don't believe in God, maybe you believe Emeril was the one who created the universe with his big BAM! :)
Next time Micheal, try reading your own link before making foolish statements like "glass is not a liquid". This is from your link, verbatim.
"Conclusion
There is no clear answer to the question "Is glass solid or liquid?". In terms of molecular dynamics and thermodynamics it is possible to justify various different views that it is a highly viscous liquid, an amorphous solid, or simply that glass is another state of matter which is neither liquid nor solid. The difference is semantic."
You might try reading that again. As Michael said, glass is not a liquid: "simply that glass is another state of matter which is neither liquid nor solid"
This would be a cool conversation piece around the home, and to pass on the your grandkids, so where does one obtain pitch?
The Viscosity of Pitch: Compared to Waiting in the Queue at one's local bank. After a long wait, I often mention to my queue-mates that I was a young man when I started waiting, and now I have gray hair, and am old, etc. Another one, the money I brought to deposit was once worth something when I came here, now it won't buy " ".
Rapidweather's Linux Screenshots.
A fluid is something that will change its shape to its container. A liquid is something that has spesific chemical properties, and may not be a fluid. That's why glass can be a liquid, but not a fluid. Read the artical.
autopr0n is like, down and stuff.
In Michael's defence....
The article states that glass can be considered either a solid or a liquid.
but it is definately not a FLUID
Fluid does not mean liquid
liquid does not mean fluid
Glass does not flow. A chunk of glass in a jar will not, over time, flow to fill it up evenly.
A chunk of glass in a funnel will not slowly drip out the bottom.
Window panes do NOT flow towards the bottom, making the bottom thicker. They were simply made that way becuase of the manufacturing process of the times.
Glass is not a fluid (unless you get it really hot, in which case it most certainly is a fluid)
How hard would it be to hook up a slashbox to the pitch cam?
I mean.. that way it would gaurentee that someone would see the drop (how often is it that no one is at slashdot?)
and as an added bonus, we are probably the only mass audience nerdy enough to actually enjoy it
Amateur Telescope Makers often call pitch "funny stuff" since it will behave in different ways with just minor changes in the environment or handling.
The cool thing is that someone figured out how to make use of the properties long before we understood why it does what it does.
Another interesting use for the terribly versatile material called pitch is to form the precursor material (PAN) for Carbon (also called Graphite) fibers used in the modern Carbon composites that make everything from tennis rackets and fishing rods to airliners and the leading edge surfaces of the space shuttle.
The fibers produced by this process are very fine - typical "tow" widths are 12,000 fibers (about the diameter of a small string), 6000 fibers, and the fairly fine 3000 fibers.
We'd have a hard time getting by without pitch in today's world...
"The future's good and the present is nothing to sneeze at." - Roblimo's last
So did the Buddha r00t the universe too? Or did he just fall victim to the honeypot?
2^5
Go have a look at the live stream.
Glass is melted down silicon that has been formed into glass and then cooled. When it's cooled, it is the same temperature as silicon, and because Silicon is a solid, Glass would have to be a solid. Everyone has forgotten about that. And anyway, pitch is a liquid, glass is melted-down silicon, making it NOT A LIQUID. So, there is a clear answer, making Micheal correct.