The Pitch Drop Experiment.

June 6, 2002 8:52 PM

The Pitch Drop Experiment. Everyone should know by now that 'glass is a supercooled liquid' is an urban legend. But there are true liquids that appear solid at room temperature. Pitch, a petroleum derivative, is one of them. The Blair Pitch Pro Pitch Drop Experiment, begun in 1927, drips pitch out of a funnel, at roughly one drop every ten years. It has a webcam [RealPlayer req.], with a short canned loop of audio explaining the experiment's origins. I tell you, I'm on the edge of my seat watching this thing!
Swiped from The Cellar.
posted by Slithy_Tove (22 comments total)

"In the 69 years that the pitch has been dripping no-one has ever seen the drop fall."
I wonder what the story is behind that. Did it fall unexpectedly during the night, or did the scientist in charge of watching the drop fall take an ill-timed bathroom break?
I can only imagine the "d'oh" moment-- the drop of pitch only falls once every ten years, and it just got missed again. "Nooo! Not again!"
posted by bonheur at 9:21 PM on June 6, 2002

Meanwhile, somewhere in Kansas, grass is growing.
posted by yhbc at 9:28 PM on June 6, 2002

This is cool. It doesn't seem like a drip in the realvideo, it seems more like a big gooey dollop that has already reached the beaker, and is just waiting to break off from the rest of the pitch. Still, it's really fascinating to think that something we think of as hard as a rock can exhibit such different properties. The cloche that it's under is really pretty - the whole thing has a very sculptural quality to it. And I love the little 9volt battery (there as a size comparison, I presume).

Also, 1927 + 69 = 1996 (the probable date of this website), so I think the 8th drop has already fallen. I hope they get a real cam so we can watch the 9th fall, oh, about 2 or 3 years from now. Someone has to see one of these drops fall! But imagine how excrutiatingly boring the cam would be in the meantime.
posted by iconomy at 9:29 PM on June 6, 2002

: turning off the sarcasm :

Okay, that's dang cool. And I do like the "Blair Pitch Project" bit. But I'm not going to leave the webcam on all night, regardless.
posted by yhbc at 9:30 PM on June 6, 2002

[offtopic]

Iconomy - what happened to your 'blog? Do regular readers now need a password to get their fix, or what?
posted by yhbc at 9:32 PM on June 6, 2002

Okay, I still thought glass was a liquid. Even after reading the FAQ linked by Slithy, it appears as if it is really a "frozen supercooled liquid", or "a liquid which has lost the ability to flow". So it's a liquid and a solid? Please Hope Me...
posted by kokogiak at 9:37 PM on June 6, 2002

yhbc, I have a note about it on my userpage. thank you for asking ;)
posted by iconomy at 9:44 PM on June 6, 2002

I was still under the misimpression that the glass legend was true, too. Damn my public school education for letting me wallow in ignorance for so many years! But thank you, Slithy, for filling in the gaps. ;-)

It seems that this whole shattering pitch thing might ring a bell. Come to think of it, silly putty does the same thing, too... pull it slowly and it stretches, pull it hard and it breaks. What is the property called that explains this?

I also remember hearing about some people who had to jump off of a damaged oil platform some years ago. Two or three hundred feet down to the water. The platform was so high that they were breaking arms and legs on impacting the ocean. So once again, dive in(relatively) slowly and the water parts for you, but come in at high speed and it's like hitting pavement. Is this just another aspect of viscosity, or some other property? Any physicists out there?
posted by Jonasio at 9:57 PM on June 6, 2002

I haven't had the energy to dissect all the quotes in the paper about glass that's linked to, but the following one illustrates the problem with all this classification into solids vs. liquids:

"Glass includes all materials which are structurally similar to a liquid. However, under ambient temperature they react to the impact of force with elastic deformation and therefore have to be considered as solids."

Well, if that's the case, then pitch is a solid, too, since the Pitch Drop Experiment website has a photo and video which show that pitch, too, reacts to the impact of force with elastic deformation (namely, shattering).
posted by delfuego at 10:12 PM on June 6, 2002

During second grade I remember reading somewhere that glass was a liquid. That same year my science teacher tried to argue with me, the all-knowing six year old, that it was indeed a solid. Later on, I seem to remember him saying something about amorphous solids, but I mostly remember feeling so proud that I knew something the teacher didn't. Oh well. Another childhood memory shattered by the truth. Anyone remember Oobleck, that stuff made by mixing corn starch and water? I rember it would break easily, but still flowed right through my fingers if I let it. Fun times...
posted by pheideaux at 10:31 PM on June 6, 2002

I did research with glass in college. We treated them very much like solids. The structure of the alkali borate and borosilicate glasses we worked with was very defined. There were certain structural units that showed up in predictable quantities based on the amount of alkali in them, strongly resembling a solid much more than a liquid.

That said, we made some pretty odd glasses. To make most of our glasses, we had to heat the ingredients in platinum crucibles, some to temperatures exceeding 1200C (a friend of mine melted one of his crucibles -- the melting point of platinum is ~1760C (3200F) -- when the furnace freaked out).

We made some of them in a nitrogen atmosphere because they would melt in the presence of oxygen. Others would turn to crystal if we didn't cool them fast enough. In extreme cases, "fast enough" meant pouring the molten glass between two polished metal rollers spinning at several thousand RPM very close to each other. If you were quick enough with the pouring, little flakes of glass would come flying out the other end of the rollers.
posted by jkottke at 10:55 PM on June 6, 2002 [1 favorite]

That's alot of work to make a bong.
posted by euphorb at 11:44 PM on June 6, 2002 [1 favorite]

I agree that the stuff in the urban-legend debunking is difficult for the non-chemist/non-engineer (me, for example) to follow the subtleties of. I think the bottom line is this: glass will not run, no matter how long you let it sit. The fact that 200-year-old glass panes are thicker at the bottom is an artifact of the way they were manufactured, not the result of the glass 'running'. Pitch, on the other hand, will run.

The experiment itself is an obvious example: the pitch is in a glass funnel. The pitch runs, but very, very slowly. The glass funnel doesn't.

This doesn't mean that another liquid wouldn't run much more slowly, say over thousands or millions of years, or run in higher gravity. But if I understand correctly, glass doesn't run at all, because it is not a liquid.
posted by Slithy_Tove at 12:20 AM on June 7, 2002

Supposedly, all metals are liquids--it's just that we often don't have the relative amount of heat and/or time to see it "flow." Once you think about the properties of matter outside of our own reflexive time, you begin to realize that we take a lot of our universe for granted. We naturally expect our metals to be solid and our rubber to be pliable and our water to be wet... How fortunate we are to be on a planet where the elements are hospitable to its inhabitants (for the most part).
posted by Down10 at 2:21 AM on June 7, 2002

How fortunate we are to be on a planet where the elements are hospitable to its inhabitants

Of course we wouldn't notice if we weren't...
posted by Spoon at 3:29 AM on June 7, 2002

Slithy, you're exactly right. The urban legend is not that glass is a liquid but that "glass flows" and a friend of a friend of mine saw some glass that had been sitting so long that it had run a little bit.
posted by straight at 6:56 AM on June 7, 2002

iconomy, the incomplete drop is a result of the beaker filling up. There are discussions underway about possibly remedying this situation.
posted by MrMoonPie at 8:17 AM on June 7, 2002

They should sell these things. It might be a neat thing to put into a new building... if you didn't think someone was going to tear it down in a few years.
posted by Wood at 10:12 AM on June 7, 2002

Fun is-it-a-liquid-or-a-solid experiments can be done with nothing more than a large bowl, corn starch and some water. If you try to punch the substance, you'll find it's a solid. But, if you scoop some up in your hand, it turns into a liquid and drains out between your fingers. If you quickly grab a hunk of it and roll it in your palms, making a ball, it will stay solid for as long as you keep agitating it. but, as soon as you stop, it turns back into a liquid. Substances like this are known as non-Netownian liquids.
posted by skwm at 12:28 PM on June 7, 2002

How fortunate we are to be on a planet where the elements are hospitable to its inhabitants

...which is basically the premise of the Anthropic Principle.
posted by skwm at 12:31 PM on June 7, 2002

It is for threads like this that I read MeFi. Totally random, didn't even know I was interested in it until I read it, and I leave knowing something I didn't know before.

Cool. Thanks, skwm and Slithy.

And it seems like the Anthropic Principle is just the argument from design redux. But what do I know. I amusing myself punching bowls of cornstarch.
posted by BitterOldPunk at 3:53 PM on June 7, 2002 [1 favorite]

skwm: Interesting link. I've never heard of the Anthropic Principle, but it does sound familiar. I like how it ties the whole universe(s) together in all four dimensions.

However, the sheer length of the page and the odd MS Paint-style graphics are a bit remeniscent of Time Cube, though it comes across much less offensive/insane/ridiculous to the reader.
posted by Down10 at 3:01 AM on June 8, 2002