The phrase “passing the acid test” gained popularity in the gold-rush years of the 1850s when miners used strong acids to determine whether the metal they had found was real gold or not. If it bubbled and frothed on contact with acid, it wasn’t gold. But even these failures produced something interesting and beautiful.

When pure metals cool, they solidify into intricately interlocked crystals. You can’t see the crystals because they fit together perfectly to form what appears to be a uniform mass with a smooth, solid surface. But acid can reveal the structure inside.

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About 230 years ago, molten lead that rained from the sky—historically something to avoid at all costs—became a clever new way to manufacture an important commodity: shotgun ammo.

Precisely round pellets fly straighter, but casting each in its own 1/8-inch mold isn’t exactly mass production. In space, making them would be easy. In zero gravity, surface tension pulls any liquid into a sphere, the shape with the least surface area for a given volume.

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If you want a scientific display of the dangers of pent-up stress, Prince Rupert’s drops are it. After the trauma of being dropped molten-hot into a bucket of cold water, these glass balls, named for a 17th-century amateur scientist, turn into bundles of high tension. They’re impervious to even the strongest blows, until you find their hot button: Flick the tail, and they explode.

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If you ever see a large industrial metal fire (yes, they happen) on the news, you may be surprised at what the firefighters do to extinguish it: nothing. Several metals, including lithium, sodium and magnesium, can burn easily, and from time to time large amounts catch fire in factories. But even heaps of burning metal need not cause immediate panic. They don’t blow up; instead they tend to build up ash that chokes off their oxygen supply, so they slowly burn out.

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Self-heating soup sounds like something from the future: Push a button on the can, and three minutes later the contents are piping hot. But its widely available today, along with self-heating coffee and hot chocolate. In Japan, I even found self-heating sake. Pretty high-tech!

Or not. In fact, these products use a chemical reaction known since at least 4000 B.C.—the mixing of quicklime and water. When you roast limestone at about 1,650�F, it converts to quicklime, a powder used to disinfect corpses in war zones. Mix quicklime with water, and it grabs and binds the water molecules, releasing lots of energy in the form of heat. (The material left over, known as hydrated or slaked lime, is the basis of lime mortar, popular in the Roman empire and still used today.)

Soup is OK, but I decided to use the technology to make a self-heating hot tub.

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Oxygen is a good thing. Oxygen is life. But if it were much more than one fifth of our air, wed be in serious trouble. The other four fifths is nitrogen, an almost completely inert, obstructionist gas whose main effect is to get in the way of the oxygen, especially where flame is involved. For every bit of oxygen a fire consumes, it has to heat up and push away four times as much useless nitrogen. With pure oxygen, that damper is gone, and things that merely smolder in plain air go up like dry tinder. In 1967 three Apollo 1 astronauts died in a raging fire when Velcro lit up in their pure-oxygen pressurized space capsule.

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There are many unusual things to see around Newton Falls, Ohio—the Wal-Mart with hitching posts for Amish buggies, the Army base with helicopters and tanks proudly arranged on hills—but I was here for the most unusual thing of all: the local Dynamitron. I was here to make frozen lightning.

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I think Apple sells fantastic objects that look like they came from the future. And apparently, in that future we all live in velvet rooms and have no fingers-there´s no other way to explain the ultra-shiny mirrored backside of my new iPod nano, which got scratched and grungy with fingerprints in exactly three seconds. So I gave it a nifty scuff shield and, while I was at it, my own logo, using a superthin layer of electroplated copper.

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