Microwave ovens

The microwave is a miracle of World War II innovation, the result of radar technology shrunk down to the size of a breadbox. They’re capable of cooking more quickly and efficiently than a conventional oven… just not as deliciously.

Microwaves are still omnipresent in this culinarily conscious era, but have assumed a secondary status in the kitchen, relegated to reheating and defrosting far more than actual cooking. But sales are back up as companies fit new trends into old TV-dinner containers—and there’s always the entertainment factor of watching peeps expand, grapes melt, and aluminum foil pranks in action. Ding!

2.45 billion: Times per second microwaves’ positive and negative fields move

80%: Energy savings of a microwave oven compared to a conventional oven

90%: Share of households in the US that have a microwave oven

$750 million: US microwave oven market in 1976

$3.7 billion: US microwave oven market in 2006

5%: Share of households in India with microwave ovens in 2013, compared to 31% for refrigerators

65%: Share of the more than one billion pounds of popcorn Americans ate in 1995 that was microwaved

10,000: Copies sold of the 1986 classic, Microwave Cooking for One

12: Points per game averaged by basketball player Vinnie “The Microwave” Johnson

Magnetrons, or “high-voltage motors that output energy in the form of microwaves rather than mechanical work,” are at the heart of the microwave oven. A filament heats up at the core of the magnetron, releasing electrons that loop around a circular magnet surrounding the filament. That circular magnet has cutouts, “resonating cavities” that look like petals of a flower. When electrons flow around those cavities, they work like simple LC circuits, pumping microwaves at a resonant frequency determined by the size of the cavities—typically 2.4 GHz—into the oven.

When the bending microwaves hit the food, the positive and negative charged ends of water molecules move back and forth to align with the current from the microwave’s electromagnetic field. The molecules are moving back and forth so quickly from the high frequency of the microwaves that it causes friction, which turns into heat.

The other trick is keeping the microwaves in the oven. That’s done by surrounding the inside with a Faraday cage, a conductive box that absorbs the specific microwave frequency of the oven. That’s the mesh you see in the oven’s window. In the US National Radio Quiet Zone, 13,000 square miles free from electromagnetic interference, the microwave in the control room of the 2.3-acre Green Bank Telescope is itself kept within a Faraday cage.

“Revenge is a dish best served in something microwaveable.”

—And That’s Why I’m Single by Josh Stern

1933: At the Chicago World’s Fair, Westinghouse cooks food between two metal plates paired with a 10-kw shortwave radio transmitter.

1940: Randall and Harry Boot create 10-cm microwaves—unheard of at the time—with a cavity magnetron.

1945: While working on radar, Raytheon’s Dr. Percy LeBaron Spencer walks past a magnetron vacuum tube and the chocolate bar in his pocket melts. He repeats the test with a popcorn kernel—the first microwave popcorn.

1947: Raytheon creates the first microwave oven, the Radarange; over 5 ft (1.5 m) high, it’s only used in commercial kitchens.

1954: Raytheon introduces a commercial microwave oven, the 161 Radarange, at $2,000–$3,000 ($16,000–$24,000 today).

1955: Tappan Stove Company produces the first domestic microwave oven with Raytheon technology; it costs $1,295 ($10,500 today).

1960s: Litton Industries develops the device’s now-common short, wide shape.

1966: Japan’s Sharp Corporation introduces a microwave with a turntable to more evenly heat food.

1967: Amana Corporation, owned by Raytheon, creates a countertop Radarange for just under $500 ($4,000 today).

1970: 40,000 microwave units are sold in the US.

1975: Microwave ovens begin outselling gas ranges in the US.

1993: More than 80% of American households and 75% of American workplaces have a microwave oven.

2006: A Pew Research study finds the only appliances Americans find more essential than microwave ovens are cars, washing machines, dryers, and air conditioning units.

When microwaves finally became affordable for consumers, a craze of strange, new recipe ideas took off in kitchens across America in the late 1970s and 80s. Beyond TV dinners and Mug-O-Lunch pasta cups, cookbooks catered to microwaves, with dishes like asparagus soup and roast beef browned with Worcestershire sauce and mushroom ketchup. It was part of a larger trend of two-income families, and a new era of more women working outside the home with fewer hours to spend in the kitchen.

But times and taste buds changed, and sales of microwaves began to decline by 2000, dropping by 25% year over year. “Americans have this weird relationship with science and food. In some eras, they really trust what scientists are telling them and believe in the latest gadgets and nutritional science,” Ken Albala, a food historian at the University of the Pacific, told The Atlantic.

Microwaves also don’t create the Maillard reaction—the deep flavor of caramelized onions or the browned bits on the outside of a pan-seared steak. That requires an oven or pan’s heat to dry out the surface of the food in order for the reaction to take place, creating a chemically complex deliciousness. The efficient, even heating in a microwave merely excites water molecules, so food can come out mushy.

But just as Albala says, food trends and tastes come in cycles, and it appears the microwave is making a comeback. The number of microwaves shipped to US retailers has increased in the past four years. Manufacturers have rebranded TV dinners as healthy, quick fixes, with minimalist labels and trendy subway advertisements. There are new contraptions and hacks, from the pasta boat and mug cake, to a sandwich grill, rice cooker, and even a pressure cooker all designed for the microwave.

A microwave’s distinct humming sound comes from the transformer, diode, and capacitor vibrating. The whooshing sound is created by a fan that blows air onto the magnetron to keep it from overheating.

Microwave ovens are so commonplace in our lives that it’s hard to believe that the technology was first intended for use in wartime. This short documentary explores all the strange moments that led to microwave ovens becoming a common household item—at which point their magic turned pretty corny.

The challenge that took over TikTok in 2019 doesn’t feature a single microwave. The name came from the original creator of the move, TikTok user @djtaylortot, who filmed himself spinning on the ground to Japanese pop singer Joji’s song “Dancing in the Dark” and called it “DJTaylortot Microwave Chain.” Soon, the trend took off, turning into a meme with thousands of people posting videos of themselves trying to spin with one hand—or for the more skilled, without any hands—as though they were moving without any assistance, sort of like a microwave turntable.

Though it’s hardly the only microwave cookbook to get roasted—or perhaps, reheated—on social media, Marie T. Smith’s Microwave Cooking for One has been called “the world’s saddest cookbook.” But as Jeremy Glass writes for Thrillist, Microwave Cooking for One represents years of diligent experimentation with some solid results (though you might want to pre-sear your microwaved steak).

For a more modern take on the genre, check out the recipes of British food writer Jack Monroe, aka the Tin Can Cook.