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You see Ken Miller’s smoke displays at NFL games and air shows. What you don’t see are the explosions, DIY rockets, and smoldering craters that speckle his Minnesota farm. His personal pyrotechnic experiments don’t belong on the 50 yard line or in anyone’s backyard.

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Hot rod

Ken Miller launches a red signal flare, which can rocket up to 1,200 feet, off the hood of his poor truck and into the foggy night. He buys the devices from industrial suppliers and typically harvests their innards for his own projects. The ­powdered ­aluminum-​­magnesium alloy is a choice fuel.
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Trial and error

Meet the Hedgehog: 18 flares epoxied upside down to a wire rack. It’s a work in progress. Miller’s initial ignition plan was to yank a rope attached to the torches’ triggers (covered here by protective rubber caps), but the cord got stuck and fizzled his light show. He has plans for an even bigger version.
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Rocket man

Miller’s career in pyrotechnics started more than three decades ago, making 12-inch-diameter 50-pound aerial bombs that burst into pulsating strobes. Though he’s moved into the niche smoke-​display business, he still makes rockets—often flares hot-​­glued ­together—​for the joy of it.
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Go or no go

This nearly 3-foot-tall, 5-pound, three-stage shuttle gets its boost from three rocket flares. When Miller launched it near his alfalfa field, the contraption rose 1,000 feet, then veered suddenly to the right. A parachute built into the tip kept it from violently crashing.
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Fountain

Blasting 100 feet up from a 2-foot-deep hole, this eruption is the result of ignited magnesium interacting with groundwater. It’s roasting at about 4,000° Fahrenheit and is silent, except for a buzz that warns it’s about to blow. Like most of Miller’s creations, it’s best observed from a distance.
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Night shift

In a roughly 2,000-square-foot shop, Miller toils into the night with a hydraulic press, packing powdered chemicals into cardboard cartridges. Housing combustibles is perilous work: Miller’s business partner died 18 years ago when 44 pounds of potassium chlorate ignited their former warehouse.
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Pack of smokes

Miller’s professional products are more refined (and safer) than his backyard bangers. The packaged plumes, seen here with color-coded labels and electronic fuses, appear in air shows and as car-crash smoke in action-movie franchises, including one of the early Transformers films.
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Hell hole

Friendly discussions and debates on Miller’s farm can end in bottomless potholes. This magnesium-caked bore—gouged by a ¾-inch-wide, 4-foot-long cartridge—proved to one group that a skinny torch can outboom a fat one. The explosion shook the ground hundreds of feet away.
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Cloud and clear

Good smoke volume, Miller says, “is the result of the correct mix of chemicals and confinement.” He creates a dense and tactile quality—which sometimes makes plumes look like billowing ­velvet—​by compacting his explosives (here it’s red dye, sugar, and potassium chlorate) just the right amount.
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Dry heat

For no good reason, Miller and his cohort packed 500 pounds of magnesium flares into a junked dryer and set it alight. The internal temperature hit about 1,800° Fahrenheit—hot enough to boil steel. The whole thing would have melted into a puddle, but the ceramic coating held it together.
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