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.

Comments

Did michael read his "glass is not a fluid" link?

[pmc]

Apparently not, or the link would have been "Is Glass liquid or solid?", the actual title of the article. I'll repeat the start of its conclusion here:

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.

Why bother with pitch when there's Thinking Putty!

[bons]

Puttyworld has a great explanation on why Thinking Putty can flow like a liquid and still shatter when hit with a hammer.

And it's more fun to play with than pitch.

Re:Did michael read his "glass is not a fluid" lin

[pmc]

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.