Finding the Viscosity of Pitch 324
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.
A watched pitch... (Score:2, Funny)
Time Lapse anyone? (Score:2)
Any commend line JPG -> MPG converters out there???
Re:Time Lapse anyone? (Score:2)
I like JPGVideo [ndrw.co.uk] a lot, since I can choose any encoder I have.
Dave
What do you mean? (Score:2)
Keeps us from getting bored (Score:5, Informative)
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.
Re:Keeps us from getting bored (Score:5, Funny)
Oh wait, this isn't in the US, is it? Nevermind...
Re:Keeps us from getting bored (Score:3, Funny)
In these experiments, they sealed jars of some sort of growth medium which was sterilized. By showing that nothing grew in them, they disproved the theory that life was "spontaneously generated", and that it comes from previous life. They still have the sealed jars on display.
Dad always said he was tempted to sneak in at night and stick a mouse inside one of the jars.
Re:Keeps us from getting bored (Score:2)
Re:Keeps us from getting bored (Score:2)
You don't have to be rich to go to a good university. Many excellent state schools (UCLA and UIUC are 2 off the top of my head) are about $4000-$8000 per year for state residents (sometimes less). There are a ton of academic scholarships and student loans which can make the cost essentially zero until after graduation.
Cornstarch and Water (Score:4, Interesting)
Re:Cornstarch and Water (Score:2)
Fill one end of the tube with cornstarch, and blow on the other end, directing the cloud towards the flame source.
You'll want a tube that is arms length or better, if you value your eyebrows.
Fun with cornstarch in science class.
Re:Cornstarch and Water (Score:2)
~GoRK
non-Newtonian fluid (Score:4, Interesting)
-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.
Re:non-Newtonian fluid (Score:3, Interesting)
For real fun, juggle two blobs of this stuff and one of those plastic toroidal tubes of water, and remember which ones to squeeze each time...
Re:non-Newtonian fluid (Score:2)
Egads! He's invented silly putty!
Re:Cornstarch and Water (Score:3, Interesting)
stealthy osdn slashvertisement (Score:3, Interesting)
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.
It will take several years (Score:2, Interesting)
Re:Keeps us from getting bored (Score:4, Funny)
The Fluidity of Glass (Score:4, Informative)
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!
Re:The Fluidity of Glass (Score:5, Funny)
A: Yes.
Seems like a clear answer to me.
Re:The Fluidity of Glass (Score:2)
Re:The Fluidity of Glass (Score:2)
Re:The Fluidity of Glass (Score:2)
I think that you're forced to talk about degrees of translucency.
Re:The Fluidity of Glass (Score:3, Interesting)
typically the colored pieces of stained glass windows are separated by a border of lead and tin i believe. this would prevent them from blurring. i once saw a presentation on this, and the lady giving it said people who make glass look at glass from ancient rome. evidently they provide good data points.
Re:The Fluidity of Glass (Score:3, Interesting)
If not, and you find exampls where say the top of the glass is thicker pretty frequently, then the idea that glass flows isn't as compelling as the idea that only in modern times have we been able to mass produce industrial quality, evenly flat panes of glass.
But even if the panes are generally thicker on the bottom, what does that mean? Maybe it was easier / safer / more reliable to set the thick end of the glass at the bottom. Maybe it's easier to install that way. Maybe experience showed that glass set that way held up longer. Who knows?
Either way, "melting glass" is only one of several explanations, with others including "no difference" and "difference can be explained by work practices", and it isn't clear which if any explanation is the valid one.
Re:The Fluidity of Glass (Score:2)
I'll let my 3 year old answer that one.
Yummy.
Re:Stained Glass (Score:2)
Boy, you must be real fun to have lunch with
Wow!!! (Score:2)
Re:Glass DOES flow (Re:The Fluidity of Glass) (Score:2)
Re:Glass DOES flow (Re:The Fluidity of Glass) (Score:2)
His conclusions are flawed at best.
Telescopes doomed? (Score:2)
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.
You are wrong (Score:2)
Re:Glass DOES flow (Re:The Fluidity of Glass) (Score:2)
Or: People couldn't make perfictly flat glass, and chose to put the fat-side down to make the window more stable.
An epiphany! (Score:4, Funny)
did it drop already? (Score:2)
Kelvin's experiments (Score:5, Interesting)
Its usually on show in either the Hunterian Museum [gla.ac.uk] or the Department of Physics and Astronomy [gla.ac.uk] 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...
Re: Kelvin's Pitch Glacier (Score:3, Interesting)
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.
Re: Kelvin's Pitch Glacier (Score:2)
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)
Re: God's experiments (Score:5, Funny)
In reality God is a hacker who rooted the Universe.
So yes, it's a big experiment (read: Honeypot project)
Re:Kelvin's experiments (Score:2)
Did michael read his "glass is not a fluid" link? (Score:4, Insightful)
Re:Did michael read his "glass is not a fluid" lin (Score:3, Informative)
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...
Re:Did michael read his "glass is not a fluid" lin (Score:3, Insightful)
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.
fluid != liquid (Score:2)
Re:fluid != liquid (Score:2)
well, read the artical (Score:2)
Re:Did michael read his "glass is not a fluid" lin (Score:3, Interesting)
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
no, glass does *not* flow (Score:2)
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.
Couldn't resist... (Score:5, Funny)
Minor nit to pick. (Score:2)
Re:Minor nit to pick. (Score:2)
I was confused by that point as well. There is also this page [uq.edu.au] -- the link is right there at the top -- that states:
- "Technically speaking, the eighth drop in Parnell's famous Pitch-Drop demonstration experiment "fell" at the end of November last year, while I was overseas. Unfortunately the high-tech webcam's digital memory also suffered a bout of amnesia at the crucial moment. That was not all, however. When Parnell set up the demonstration in 1927 he could not have foreseen that during the gestation years of the eighth drop the University would decide to air-condition the two large lecture theatres in whose foyer the pitch resides, thus reversing the drop's seasonal experiences. That drop became by far the largest in the series, and when the time arrived for it to fall there was insufficient depth to the bottom of the beaker below for it to suffer a complete break."
Seven? Eight? Seems even they don't have a handle on it.The two numbers are right next to each other no matter where on the keyboard you look. I can imagine someone mistyping it... it's not as if the page needs updating all that often. (Looks like the last update was 9 Apr.) Here's hoping they read /., notice this thread, and make the change. (Yeah, right.)
Re:Minor nit to pick. (Score:3, Funny)
Nope (Score:4, Informative)
In fact, another page [uq.edu.au] confirms that the 8th drop fell in November 2000, so it is indeed the 9th drop forming.
Re:Nope (Score:2, Insightful)
Re:Nope (Score:2)
-Adam
Bah! That's Nothing. (Score:2, Funny)
Re:Bah! That's Nothing. (Score:2, Funny)
Couldn't resist (Score:3, Funny)
Must be a slow news day.
Yeah, I haven't slept in 32 hours. That's funny to me.
Re:Couldn't resist (Score:2)
Looking at the amazing pitch-cam all night, were ya?
Am I the only one.... (Score:3, Interesting)
Re:Am I the only one.... (Score:2)
The plot revolves around a time machine, remember?
It's not in slow motion, it's just traveling into the future really really fast.
-
Referenced article: Is glass liquid or solid (Score:2)
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.
Re:Referenced article: Is glass liquid or solid (Score:2)
Anoyone done this quicker? (Score:3)
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!
Another phenomenon almost as slow (Score:2)
Cheese (Score:2, Funny)
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?
Re:Cheese (Score:2)
Anyway this site is a hoot, and I'm surprised it's still there. This was one of the first sites I remember on the web where someone actually committed to the then-considerable expense of registering a domain name and building a web server just for a joke. I'm glad to see this true relic of the old Internet is still hanging around (and apparently, in its original form, too...)
Pitch is used for polishing optics (Score:5, Interesting)
I have a page about telescope making [geometricvisions.com] 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.
Re:Pitch is used for polishing optics (Score:4, Informative)
Since then, high-boiling coal-tar and petroleum fractions have been formulated which resemble pitch in their physical qualities, but which are much more predictable and constant in their properties, and safer to work with (but smell like roofing tar when they're hot.) "Gugolz" pitch is a petroleum product. "Asphalt" would be a more accurate name, but "pitch" has come to mean any dark-colored organic tar.
One nit: ferric oxide (iron(III) oxide), not ferrous oxide, is the composition of red optical rouge. The cerium oxide used for polishing is the quadrivalent oxide, ceric oxide (cerium(IV) oxide), I believe.
One of the old writers (Ellison, maybe?) writes that if you put a cork at the bottom of container of pitch, the cork will eventually rise to the top. I don't know if this experiment has ever been tried.
My own mirror-making project eventually failed, by the way. I never got a good polish and eventually I gave up.
hyacinthus.
Pitch is used to build airplanes, too... (Score:2)
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...
coffee (Score:5, Funny)
Duplicate? (Score:2)
Why bother with pitch when there's Thinking Putty! (Score:3, Insightful)
And it's more fun to play with than pitch.
And by Slashdotting the RealServer... (Score:2)
Glass is not a fluid (Score:2)
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.
Re:Glass is not a fluid (Score:2)
FFS, what do you think a fluid is? Fluid is well defined in GCSE Chemistry - if not before - as something in either the liquid or gaseous states.
Also, solid was well defined as something with a very regular molecular layout and as being resistent to deformation under pressure.
Seems pretty obvious to me, looking at my windows here...
The glassy state (Score:4, Informative)
Re:The glassy state (Score:2)
So, is this how we get obsidian?
If so, what's the process?
It Dropped! (Score:2)
RealPlayer G2? (Score:2)
Flawed experiment (Score:2)
Glass as a fluid (Score:2)
From the last paragraph:
Glass liquid ? (Score:2)
Where do you get pitch? (Score:2)
Re:Where do you get pitch? (Score:2)
Pitch and astronomical mirror making (Score:2)
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.
Re:That's where I will be! (Score:2)
That would put it right up there on the Entertainment Index together with old Soviet tractor parades, Equal Opportunity Beauty Pageants For The Habitually Ugly and soccer.
apparently not many think so! (Score:2, Insightful)
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.
Far more fun (Score:2, Interesting)
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.
Re:Far more fun (Score:2)
Re:Far more fun (Score:3, Funny)
Make sure that they've signed the personal injury waver first, of course...
Hmm pity, they don't have this demo on their web page Ontario Science Centre [ontariosciencecentre.ca] only a block away from me.
I'm already there (Score:2, Informative)
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 [uq.edu.au], 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
Re:Fluidity of pitch (Score:2)
Re:Pitch (Score:2)
Heh (Score:2)
Re:Slashdot wrong again (Score:2)
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.
did you ever learn to read? (Score:2)
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.
Re:Glass (Score:2)
The process that creates uniform glass panes is less than a century old.
Why is it so hard to grasp. Glass does not flow unless molten. It is not some kind of vicsous fluid, like pitch. The glass pane in your old school looks the same as the day it was installed, except for maybe some scratching due to the elements.
Read more carefully. (Score:2)
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)