Frozen on Video: Theo Gray Sculpts in Solid Mercury, with Some Help from Liquid Nitrogen

How to cast solid, if fleeting, shapes in mercury: Just keep it at 320 degrees below zero

By Theodore Gray Posted 06.04.2009 at 10:52 am 13 Comments

Frozen Fish The frost crust forms when water condenses from the air Mike Walker

What you consider solid, liquid or gas depends entirely on where you live. For example, men from cold, cold Mars might build their houses out of ice. Women from Venus, where the average temperature is about 870°F, could bathe in liquid zinc.

We think mercury is a liquid metal, but it’s all relative. At one temperature, the mercury atoms arrange themselves into a solid crystal; at another, they flow freely around each other as a liquid. Children from Pluto (like mine, for example) could happily cast their toy soldiers out of mercury, because on that frigid planet it is a solid, malleable metal a lot like tin. Here on temperate Earth, you need a stove to cast tin, but a tank of liquid nitrogen to make mercury figurines.

At liquid-nitrogen temperature, about –320°F, mercury acts like any other metal: You can hammer it, file it, saw it. (It won't shatter like other liquid-nitrogen-frozen items because there's not enough moisture inside.) Watching it solidify is exactly like watching tin harden from a molten state. As the atoms go from liquid to solid crystal form, you see the surface pucker. And because mercury, like most metals, shrinks when it solidifies, you see the surface sink in areas, forming a patchwork characteristic of cast metal.

Pour to Scale: Room-temperature mercury poured into a cold cornbread mold Mike Walker

Nice Casting: Adding liquid nitrogen freezes the metal Mike Walker

The fun of making frozen mercury trinkets is another reason to lament the fact that this marvelous metal is also an insidious poison that must be handled carefully and never spilled. Schools have been evacuated because of one broken mercury thermometer, and mercury in the environment, particularly in fish, is a major public-health concern. Which is, of course, why I made this cute little mercury fish.

Melting Point: Above –38°F, the fish turns to liquid Mike Walker

See much more of Theo Gray's mad science in his book: Theo Gray's Mad Science: Experiments You Can Do at Home but Probably Shouldn't.

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13 Comments

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dontbother

06/04/09 at 10:58 am

cool! I would've liked to see the fish melt through the tongs though. that would've been sweet.

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rlenston

06/04/09 at 12:09 pm

Watching the fish return to room temperature would be interesting.

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walkingnerd

06/06/09 at 1:37 am

archeology and anthropology taught us that igneous glass makes very sharp knifes ...
so what property does frozen mercury have that will make it unique ?
will it slice through water like tofu ???

Ceeson

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doniv

from chennai , tamilnadu

06/10/09 at 12:47 pm

"Schools have been evacuated because of one broken mercury thermometer"

Is it true ??
In our high school we use mercury from a plastic bottle with bare hands to do physics experiments . Forgot its name , still remember stealing some of the mercury hiding it in my ink pen case ...

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ninjaboy

06/22/09 at 7:53 am

that is sweeeeeeeeet!!

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