gray matter

The Fastest (and Most Dangerous) Way to Light a Grill

Go from cold to cooking in 30 seconds with a big can of liquid oxygen

About a year ago, when resident mad scientist Theo Gray pitched me a Gray Matter column on liquid oxygen, an extremely flammable energetic form of the element, he first proposed showing how to use it to light a grill nearly instantaneously. The lawyers, however, suggested we go a more tame route, so instead we showed how you could make a few drops of the hooch yourself.

But of course, when left to his own devices (and free of legal oversight), Theo couldn't help himself.

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Carve Steel with Saltwater, Electricity and a Tin Earring

Using electrochemical machining, steel can be molded with a soft, cheap piece of tin without any physical contact

I remember seeing a demonstration of a seemingly magic process at an engineering open house decades ago, in which a soft metal bit carved detailed shapes into far harder metals. It's called electrochemical machining (ECM), and it's so simple in principle that you can do it at home with a drill press, a battery charger and a pump for a garden fountain.

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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

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.

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Apple Juice

Charge your gadgets with a piece of fruit and some pocket change

Arthur C. Clarke wrote that "any sufficiently advanced technology is indistinguishable from magic," but he was wrong. It's easy to tell the difference -- technology works. For example, "remote-viewing" mentalists claim they can see events far away, yet they fail every test. In fact, remote viewing is simple: It’s called TV.

Another example that recently circulated online was a fake video of someone charging his iPhone by jamming the end of a USB cable into an onion. How do I know it was fake? First, you need contacts made of two different metals, and second, you can't get enough voltage out of a single vegetable. What makes the ruse so disappointing is that it is possible to charge an iPhone this way, if you do it right.

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Bacon: the Other White Heat

You know bacon is delicious, but did you know it contains enough energy to melt metal?

I recently committed myself to the goal, before the weekend was out, of creating a device entirely from bacon and using it to cut a steel pan in half. My initial attempts were failures, but I knew success was within reach when I was able to ignite and melt the pan using seven beef sticks and a cucumber.

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Science Projects: The Really Dangerous Book for Boys

Science Projects - introducing a new collection from PopSci's truly mad scientist

Science Projects

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Blowing (Up) Hydrogen Bubbles

A dramatic demonstration -- with exclusive video! -- of why the same gas that heats your house can also make it explode

Living in the Midwest, where heating homes with propane is common, I periodically see reports in the local paper that yet another unoccupied house has exploded. They often note that the roof was found in the basement, while the walls were spread some distance into the neighboring fields.

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Making Glass in a Grill [With Video!]

The author creates an ornament—using his barbecue

All the components of glass can be found in two places: the beach and the laundry room. It’s possible to melt pure white-silica beach sand into glass, but only at temperatures of 1,650 to 1,900°C. Washing soda, lime or borax (a traditional laundry aid) added to the sand disrupts the quartz-crystal structure of silica and reduces the required temperature to a more practical, though still dangerous, 1,100°C, which I achieved with a backyard grill and a vacuum cleaner.

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Metal's Hidden Treasure

All metal is made of crystals; you just can’t see them—without a little acid, anyway

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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Make Your Own Ammo

How do you turn molten metal into perfect spheres? Just pour it off the roof

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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Quantum Physics in a Glass

Two chemicals create a glowing (and poisonous) mixture that’s a window into the weird world of quantum physics

Before the discovery in the 1920s of quantum mechanics—laws that explain the way the world works on the very small scale of atoms and electrons—the fact that bleach and peroxide glow when mixed would have seemed like just another chemical reaction that gives off light, like fire or fireflies. But it’s actually a glimpse into the impossible.

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Shattering the Strongest Glass

Explosive glass drops demonstrate why your car windshield is so strong and safe

BANG!: Break the tail of a Prince Rupert’s glass drop, and the whole thing explodes.  Mike Walker; special thanks to Glass Lake Studio
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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Let Burning Metals Lie

There’s not much you can do to put out a magnesium fire. Douse it with water or spray it with a fire extinguisher, and the results can even be explosive

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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The Instant Hot Tub

If a few ounces of quicklime mixed with water can make self-heating soup cans, we figured 500 pounds of it could create a self-heating hot tub

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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Flaming Oxygen Drops

In large quantities, pure liquid oxygen is powerful enough to launch rockets. But even a tiny bit packs a wallop too

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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