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What Happens When You Put Grapes in the Microwave?

When microwaved, grapes create a plasma, a luminous, fiery spectacle due to their high water content and skin acting as a dielectric. This phenomenon is a dance of physics and chemistry, sparking curiosity and caution. Intrigued by the science behind everyday items? Discover more as we unravel the mysteries hidden in plain sight. What will you uncover next in your kitchen?

Some snacks are microwaveable, which saves a lot of time when you need to grab something to eat quickly. Grapes are a heart-healthy snacking choice, but most of us probably haven’t tried putting them in the microwave. After all, there’s no need to heat them up to enjoy their juicy flavor. So why do people do it? For a dazzling light show, of course! (But maybe don't try this at home).

It turns out that if you cut a grape in half, pop it in the microwave and begin to heat it, the grape will generate a fiery plasma – superheated, electrically-charged gas – caused by trapped microwave radiation creating a strong electromagnetic field.

Microwaving grapes generates a fiery plasma, caused by trapped microwave radiation creating a strong electromagnetic field.
Microwaving grapes generates a fiery plasma, caused by trapped microwave radiation creating a strong electromagnetic field.

In laboratory settings, plasma is typically generated by heating a neutral gas to an extremely high temperature, so how does this work with grapes? Canadian researchers say that a grape’s size and water content are key to how it interacts with microwave radiation. Pablo Bianucci of Concordia University in Montreal explains that “a single wavelength of microwave radiation fits almost entirely into the grape, meaning the grape can "trap" microwaves.” The tissue in each half of the grape can use the connective skin as a bridge of sorts, traveling from one half of the grape to the other. This results in a strong electromagnetic field between them, which in turn generates plasma.

While this is definitely fascinating to watch, researchers warn that it shouldn’t be attempted at home too often. Microwaving grapes will eventually damage the microwave. In fact, Trent University physics professor Aaron Slepkov went through a dozen microwaves when he first began researching the science behind grape plasma in 2013.

Seriously, don't try this at home:

  • Researchers discovered that even whole objects without a “skin bridge” between them will produce plasma as long as there is physical contact between them. They found that even whole grapes produced plasma 60 percent of the time if they were touching another grape.

  • Grapes aren’t the only food item that will generate “fireballs” in the microwave. Anything grape-sized that is made up of water will do the trick. Researchers have tried cherries, olives, blueberries, and even quail eggs. All produced the same result.

  • Bianucci’s research findings were published online in February 2019 in the journal Proceedings of the National Academy of Sciences.

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    • Microwaving grapes generates a fiery plasma, caused by trapped microwave radiation creating a strong electromagnetic field.
      By: Scanrail
      Microwaving grapes generates a fiery plasma, caused by trapped microwave radiation creating a strong electromagnetic field.