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Endimion17
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One more drop
This is not the most famous pitch drop experiment in the world, the one in Brisbane.
This is a similar experiment in Dublin, and for the first time ever, it has been recorded on video.
Behold.
<iframe sandbox width="420" height="315" src="//www.youtube.com/embed/k7jXjn7mIao" frameborder="0" allowfullscreen></iframe>
But seriously, this is very cool.
I wanted to witness the drop over streaming video so I was a bit disappointed, but later learned that this is not the original pitch drop experiment,
which is expected to give one drop during 2013, so I hope there'll be some media notifications before it actually happens.
I think it's kind of stupid they've used a timelapse video. I want to see the drop falling down in actual speed.
And they use damn webcams instead of HD cameras.
Here's the official page for the oldest experiment, by University of Queensland.
[Edited on 20-7-2013 by Endimion17]
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bfesser
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<strong>Endimion17</strong>, you are my hero! I was trying to remember what this experiment was called, but it just kept eluding me. For
some reason, I brought it up while talking at someone about long term experiments, a couple months ago. I was telling the person that I'd love to set
up one of those funnels in a bell jar filled with tar, but couldn't remember the name "pitch". Thank you so much for sharing this! I'm
<em>definitely</em> going to set one up now.
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garage chemist
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How would one obtain pitch with just the right consistency for this experiment?
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bfesser
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I have a chunk of refined <a href="http://en.wikipedia.org/wiki/Asphalt" target="_blank">asphalt</a> <img src="../scipics/_wiki.png"
/> that I picked up while the road outside my apartment had been torn apart to replace a water main. The viscosity is surely different than that
of the pitch in the above experiments, but of what concern is that? It's not exactly a quantitative experiment, more of a demonstration piece. You
can easily purchase <a href="http://en.wikipedia.org/wiki/Pitch_(resin)" target="_blank">pitch</a> <img src="../scipics/_wiki.png"
/>, bitumen, or asphaltum from lab suppliers, eBay, or local construction suppliers.
<strong><a href="http://www.physics.uq.edu.au/physics_museum/pitchdrop.shtml" target="_blank">The Pitch Drop
Experiment</a></strong> <img src="../scipics/_ext.png" /> - R. Edgeworth, B.J. Dalton and T. Parnell | Quote: | | The pitch was warmed and poured into a glass funnel, with the bottom of the steam sealed. Three years were allowed for the pitch to consolidate, and
in 1930 the sealed stem was cut. |
My plan has been to use a powder addition funnel and to simply stopper the
stem (PTFE wrapped cork) while waiting for the fluid to harden. I think I actually set aside a bell jar I found several years ago, for this exact
experiment, if I could only remember where I put it.
<strong><a
href="http://www.dailymail.co.uk/sciencetech/article-2142928/Is-boring-experiment-Scientists-watch-drops-pitch-form--75-years.html"
target="_blank">Is this the most boring experiment ever?</a></strong> <img src="../scipics/_ext.png" />
[Edited on 7/20/13 by bfesser]
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Pok
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Very cool! This pitch has a viscosity of about 2.3 * 10^11 mPa*s (water = 1 mPa*s). A really long experiment could be done with glass. The viscosity
of glass is 1 billion times larger. So each drop would take 8 billion years (?). A long time to wait, but I think it's worth the time. But in
comparison to the pitch experiment, it might be a little bit more frustrating if you miss the falling event. 
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testimento
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I think you could do similar experiment with lead. It creeps too at room temp. 
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Endimion17
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Quote: Originally posted by Pok  | | Very cool! This pitch has a viscosity of about 2.3 * 10^11 mPa*s (water = 1 mPa*s). A really long experiment could be done with glass. The viscosity
of glass is 1 billion times larger. So each drop would take 8 billion years (?). A long time to wait, but I think it's worth the time. But in
comparison to the pitch experiment, it might be a little bit more frustrating if you miss the falling event. |
No, you can't do it with glass because glass doesn't flow. It's an old myth. Glass is an amorphous solid with tiny crystal domains and that has been
discussed ad nauseam. Let's keep this pitchy, not glassy. 
No, lead is not a fluid. It does not flow. It bends, but it does not flow.
Wood bends under stress over time, too, but it will not flow.
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dontasker
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Very cool.
The glass myth was explained to me as coming from observations of old windows where the bottom was thicker than the top. Some thought this was proof
of it being an extremely viscous fluid, but was really a result of glass manufacturing being imperfect and being installed so that the thickest
section was at the bottom to help it bear the load of its own weight. I'm not sure if this is true or just a myth about a myth, but it makes sense
to me.
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watson.fawkes
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I would imagine fractional
distillation, though for this material that would ordinarily mean having access to an oil refinery.
The only reason I know anything at all about this is that I was researching an old brand name "Apiezon Wax W" from Procedures in Experimental
Physics, published in 1938, which is a vacuum sealing compound. Turns out it is still in manufacture 75 years later (datasheet). From what I can tell, its the very highest boiling (highest molecular weight) fraction from distilling asphalt. They sell two other
compounds with lower softening points that I presume come out of the same still.
So if you want to improve on the demonstration, make multiple units with different fractions so that they drop at different rates.
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unionised
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There has been, that's why you know about it.
However nobody can know exactly when it will fall so there's no way to get a media friendly prediction like "it will happen today" never mind "it will
happen at 13:45 today"
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Pok
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| Quote: Originally posted by Endimion17 | | No, you can't do it with glass because glass doesn't flow. It's an old myth. Glass is an amorphous solid with tiny crystal domains and that has been
discussed ad nauseam. Let's keep this pitchy, not glassy. |
You can. I know that the window glass is a myth (thicker at the buttom at extremely old windows), but glass has a viscosity of about 10 ^ 20 mPa*s at
room temperature. So it could be observed in some million years (but not in hundred as claimed by the original myth) that the window becomes thicker
at the buttom and in some billion years that glass forms drops like in this pitch experiment, I think.
Lead has a viscosity of 100 times that of pitch (10 ^ 13 mPa*s), so this should work as well (1 drop in 800 years).
But if the dropping time doesn't linearly increase with viscosity, these estimations (800 and 8 billion years) would be wrong.
[Edited on 21-7-2013 by Pok]
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bfesser
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<strong>Pok</strong>, where are you getting these numbers?<a href="http://www.cmog.org/article/does-glass-flow"
target="_blank"> | Quote: | <strong><a href="http://www.cmog.org/article/does-glass-flow" target="_blank">Does Glass Flow?</a> <img src="../scipics/_ext.png"
/></strong>
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.
. . .
It is worth noting, too, that at room temperature the viscosity of metallic lead has been estimated to be about 10 to the 11th power, (1011) poises,
that is, perhaps a billion times less viscous—or a billion times more fluid, if you prefer—than glass. Presumably, then, the lead ca[n]ing that
holds stained glass pieces in place should have flowed a billion times more readily than the glass. While lead ca[n]ing 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. |
</a>See Also:
<strong><a href="http://www.phys.ncku.edu.tw/mirrors/physicsfaq/General/Glass/glass.html" target="_blank">Is glass liquid or
solid?</a> <img src="../scipics/_ext.png" />
<a href="http://www.sciencedaily.com/releases/2007/08/070809130014.htm" target="_blank">Is Glass A Solid Or An Extremely Slow Moving
Liquid?</a> <img src="../scipics/_ext.png" />
<a href="http://prl.aps.org/abstract/PRL/v99/i2/e025702" target="_blank">Colloidal Glass Transition Observed in Confinement</a> <img
src="../scipics/_ext.png" /></strong>
[Edited on 7/21/13 by bfesser]
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Endimion17
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| Quote: Originally posted by unionised | There has been, that's why you know about it.
However nobody can know exactly when it will fall so there's no way to get a media friendly prediction like "it will happen today" never mind "it will
happen at 13:45 today" |
Actually, I know about this just because I've thought of it and checked it out. I don't really know why have I started thinking about it. You know,
random Wikipedia spree... huge number of tabs...
They should be able to predict it at least few days ahead.
| Quote: Originally posted by Pok | You can. I know that the window glass is a myth (thicker at the buttom at extremely old windows), but glass has a viscosity of about 10 ^ 20 mPa*s at
room temperature. So it could be observed in some million years (but not in hundred as claimed by the original myth) that the window becomes thicker
at the buttom and in some billion years that glass forms drops like in this pitch experiment, I think.
Lead has a viscosity of 100 times that of pitch (10 ^ 13 mPa*s), so this should work as well (1 drop in 800 years).
But if the dropping time doesn't linearly increase with viscosity, these estimations (800 and 8 billion years) would be wrong.
[Edited on 21-7-2013 by Pok] |
Glass was thought to be a liquid and those numbers could be early calculations based on pretty wild assumptions. However, in more recent times, glass
was found to be an amourpous solid, with perfectly static systems of molecules. It does not flow. Glass beaker will not turn into a puddle over the
next billion years.
Pitch is a liquid with horribly low fluidity. It has a totally different situation at a molecular level. Heavy hydrocarbon chains slide one next to
another at very slow speeds.
Glass is made of tiny crystal domains that are locked together. There is no flow at all. Glass rod might bend if weighted in the middle, after few
hundred millenia, but it will not flow. Flowing and bending under stress are not the same thing. Flowing requires layers of molecules sliding one next
to another, and bending is a collective distortion at a macroscopic level.
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unionised
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| Quote: Originally posted by Endimion17 | | Quote: Originally posted by unionised | There has been, that's why you know about it.
However nobody can know exactly when it will fall so there's no way to get a media friendly prediction like "it will happen today" never mind "it will
happen at 13:45 today" |
Actually, I know about this just because I've thought of it and checked it out. I don't really know why have I started thinking about it. You know,
random Wikipedia spree... huge number of tabs...
|
Actually, you checked it out via the medium of the internet.
It's still the case that you found out about it via the media.
Just a thought, but if someone is planning to set up this experiment with a camera and web link etc, might I suggest having a few different funnels
with different lengths/ diameters of stem?
That way you will get more data.
[Edited on 21-7-13 by unionised]
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Pok
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I got these viscosity numbers from several books (e.g. here - 1 poise = 100 mPa*s). My estimations of dropping time of glass and lead are based on the assumption of a linear dependence between dropping
time and viscosity. As I said, this doesn't need to be the case. If the calculations of 10 angstrom units in 10 billion years is correct, my
assumption is either not correct or these guys have other data for the viscosity of glass (e.g. 10 ^ 30 mPa*s) - if they used this value then there indeed is a rough linear dependence between dropping time and viscosity.
It's very easy to calculate the viscosity of glass at RT. You can just measure the viscosity at different high temperatures (1000 °C or so) and from
these data calculate the v. at RT. That's how I would do it.
And it doesn't matter whether glass is a liquid or a solid. Solids can also behave like a liquid. Otherwise they would have an infinite viscosity. And
they don't have it.
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bfesser
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<strong>Pok</strong>, I'd like to point out that your first reference cites "Brill 1962" for the data; presumably the same <a
href="http://www.cmog.org/bio/robert-brill" target="_blank">Dr. Robert Brill</a> <img src="../scipics/_ext.png" /> who wrote the
Corning article I posted, which states "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." If <a href="http://en.wikipedia.org/wiki/Robert_H._Brill"
target="_blank">Brill</a> <img src="../scipics/_wiki.png" />, a well respected scientist and an authority on glass, says we shouldn't
think of glass as a liquid, I think we should heed his advice.
I deduce that this is the paper the Archaeological book cites, as it's his only listed publication that year:
<del><strong>Brill, R. H.</strong> (1967) <a href="http://www.cmog.org/library/great-glass-slab-ancient-galilee"
target="_blank">A Great Glass Slab from Ancient Galilee</a> <img src="../scipics/_ext.png" /> <em>Archaeology</em> 20 (2)
pp. 89–96</del> [correct paper 2 posts down]
<strong><a href="http://en.wikipedia.org/wiki/Viscosity#Viscosity_in_solids" target="_blank">Viscosity in solids</a></strong>
<img src="../scipics/_wiki.png" />
[Edited on 7/21/13 by bfesser]
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Pok
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The paper is: Brill, Robert H. (1962) A Note on the Scientist’s Definition of Glass. The Journal of Glass Studies, 4, 127-138.
The question is: is there a threshold pressure for materials with very high "viscosity" below which they don't deform at all? If yes, this is not
viscosity but plasticity or so. My assumptions were based on these viscosity values. And if they are wrong, I also was wrong.
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bfesser
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I mistakenly read 1962 as 1967. You are correct.
<strong>Brill, Robert H.</strong> (1962) <a
href="http://d3seu6qyu1a8jw.cloudfront.net/sites/default/files/collections/6A/6ACA10D0-4EEE-43F4-AF6A-7A89F9589607.pdf" target="_blank">A Note on
the Scientist’s Definition of Glass.</a> <img src="../scipics/_pdf.png" /> <em>The Journal of Glass Studies,</em> 4,
127-138.
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phlogiston
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If you had a large pool of pitch, would it be possible to make a very slow wave on its surface? Or would the viscosity also dampen the wave
'immediately'?
-----
"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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bfesser
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My intuition is that all of the energy would quickly dissipate thermally—no wave. But speaking of viscous waves; <a
href="http://en.wikipedia.org/wiki/Boston_Molasses_Disaster" target="_blank">Boston Molasses Disaster</a> <img src="../scipics/_wiki.png"
/>.
[edit] I assume you meant rippling surface waves like when you throw a stone in a pond, not sound waves, etc.
<a href="http://www.acs.psu.edu/drussell/demos/waves/wavemotion.html" target="_blank">Acoustics and Vibration Animations</a> <img
src="../scipics/_ext.png" />
<a href="http://scholar.lib.vt.edu/theses/available/etd-12062002-152858/unrestricted/Chapter2.pdf" target="_blank">Wave Propagation in Viscous
Fluid</a> <img src="../scipics/_pdf.png" />
[Edited on 7/21/13 by bfesser]
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Endimion17
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There could be absolutely no waves on pitch. The more viscous the fluid, the stronger the energy dissipation is. Compare water, honey and lava. It's
very hard to make waves on lava.
That thing in Boston was not a wave. It was merely a flood from a burst tank. It must've been pure horror for the victims. Ever since I've seen this scene I've been terrified of molasses.
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bfesser
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As luck would have it, the alley outside my apartment window is being resurfaced today. In preparation, they poured some hot liquid pitch onto the
existing pavement (to help the new layer to adhere?). As soon as I smelled that delicious aroma blowing in through my open windows, I ran outside
with glee, small soup can in hand. I scraped up as much clean liquid asphalt as I could before it hardened (had to wait until the public works men
left, because they were giving me angry looks). I plan to try filling a funnel with it later today, and hope to take some nice photos of the shiny
black liquid--if I can keep my <em>foedis feles</em> from trying to eat it!
On a side note, does anyone know what compounds constitute that wonderful aroma? I believe they're sulfur containing, but I haven't been able to find
much, beyond that.
It's a shame I don't live in California:
<a href="http://en.wikipedia.org/wiki/McKittrick_Tar_Pits" target="_blank"><img
src="http://upload.wikimedia.org/wikipedia/commons/3/33/McKittrick_Tar_Seep_North_of_Highway_58.jpg" width="400" /></a> <img
src="../scipics/_wiki.png" valign="top" />
<em>Feles mala! Cur cista non uteris? Stramentum novum in ea posui.</em>
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bfesser
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It hasn't happened yet, right?
<img src="http://i.imgur.com/5JZLQ.gif" width="150" />
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bfesser
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[yawns] Still waiting and <a href="http://www.theninthwatch.com/feed/" target="_blank">watching</a> <img src="../scipics/_ext.png"
/>.
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Sedit
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| Quote: Originally posted by Endimion17 |
No, you can't do it with glass because glass doesn't flow. It's an old myth. Glass is an amorphous solid with tiny crystal domains and that has been
discussed ad nauseam. Let's keep this pitchy, not glassy.
|
Sorry to side track but are ya'll sure about this?
The windows to the attic in my old house where well over 150 years old and there was an obvious bulge at the base of them. They where not thicker but
there was a very obvious bend in them that looked exactly how one would expect it to look if it was a slow moving liquid. I really don't think they
where made like this as it really looked like the glass had slumped over time.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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