Grape Balls of Fire

Far be it from us to deride anyone’s childish fascination with blowing stuff up in a microwave—a foolhardy nerd rite of passage if ever there was one—and what better place to exhibit dangerous, potentially expensive shenanigans than YouTube? The experiment is simple. Take a seedless grape and slice it lengthwise, making sure (this part is important) not to cut all the way through, so you leave a little bit of skin connecting the two halves. Put it face-up in a microwave, and blam: fireworks!

So what the heck is going on in there? Grapes are chock-full of electrolyte, an ion-rich liquid (a.k.a. “grape juice”) that conducts electricity. Each grape-half serves as a reservoir of electrolyte, connected together by a thin, weakly conducting path (the skin). Microwaves cause the stray ions in the grape to travel back and forth very quickly between the two halves. As they do this, the current dumps excess energy into the skin bridge, which heats up to a high temperature and eventually bursts into flame. At this point, the traveling electrons arc through the flame and across the gap, ionizing the air to a plasma (which itself can conduct electricity) and creating the bright flashes you see.

And that notion about poisonous gas tainting your roommate’s Hot Pocket? Well, the guy’s talking about the ozone generated when the air inside the glass is ionized. “Poisonous” might be too a strong word in this scenario (a little ozone definitely won’t kill you), although high concentrations of ozone can oxidize lung tissue and have been known to cause asthma in urban inversion-bowls like L.A. and Mexico City.

Again, DON’T TRY THIS AT HOME. Microwave ovens + biological capacitors = bad news. —Martha Harbison.

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Comments

[Ricky Neal, Jr.]

Popular Science not previewing the swears inserted into this video? Shame on you. This can easily be accessed by a student in a school setting. Are you people out of your mind?

Ricky Neal,

Grade 6 Science Teacher

[J-man]

First off, if your grade six students are looking up how to make home made plasma, I think swearing is the least of your concerns.

[Stan Flouride]

Secondly, if you think your sixth graders haven't heard any of those words you're deluded.

[Sean]

Thirdly this is a rare chance to actually SEE some plasma. It's rather cool really. They should do this as an experiment in schools (in controlled conditions of course).

[Gino]

They tell us not to do it, but how many of us are going to remember to add a bag of grapes onto their grocery list?

[Lou Quarm]

J-Man, and others. If you think that simply because young children may have heard gutter talk elsewhere makes it okay for PopSci to post it on their website, you are an incredible jerk. I agree with Teacher Ricky Neal: Shame on Popular Science and shame on you, J-Man, for not recognizing a reputable magazine's utter lack of sense or sensibility.

[Ben Dover]

I agree with J-man. And Gino, who calls someone a jerk nowadays douchebag?

[Alpha Kenny Wun]

How lude of you, Ben Dover.

[Luke]

I think somewhere the teacher is softly crying that his opinion isn't shared and that Ben Dover's spelling reflects his simple nature.

[Dan]

So I tried this at home before I read this article, the good news, my micro and I are still standing. Want more fun, I was part of the Tesla club at my school and you can do the same thing by creating a half-wave antenna to catch the waves and some pencil lead (carbon as in the grape skin) as the tip to toss up the same kind of plasma. Want some extra fun, you can catch the plasma balls in glass (prob. want to use pirex) and you can watch them burn - just invert a glass or something over the grape..... er don't try this at home...

[Dan]

k, so maybe the vid shows the glass thing.....

[Luke]

Errrr..... I didn't realize the names are displayed below the comments... Make that Alpha Kenny Wun with the spelling "impairment" .

[Brad Justinen]

I agree, although i have no problem with the swearing, I am surprised popsci would post this, even in there blog. A magazine as long running as Popular Science has a reputation to uphold. I am surprised that all you computer nerds don't realize this.

[kobe bryant]

hey
IM a grade 9 student, and this is the only website our buisness teacher lets us go on. I agree, the use language will lower his opinion of this site/magazine

[kobe bryant]

hey
IM a grade 9 student, and this is the only website our buisness teacher lets us go on. I agree, the use language will lower his opinion of this site/magazine

[heather]

I think Popsci was wrong to have that language. What intelligent person would use a four letter word anyway.

[Nathan]

I can't believe this is even an issue. Swearing?

First, who is the author of the article?
Martha Harbison

Does the guy in the video look like a Martha?
Not really.

Do you really think that this video was posted by someone at PopSci??? It's a YouTube video. Anyone can post a YouTube video. Obviously Martha chose a good video with some cool science in order to educate us. If you can't get over a few swear words, then at least keep your crying to yourself.

Martha Harbison, excellent job, and thank you.

[JRIcky]

This just caught my attention:
While the grape is burning under the glass, it seems to move to the left just before it produces its second wave of plasma.

I dunno, I just thought it was interesting.

[JRIcky]

It even moves once more after the second wave of plasma.

[Michael]

Let's face it. We'd all like to see this first hand and probably will "try this at home".

[hmm]

man i want a grape in a bad way right now

[TB]

I don't know why people always get bent out of shape over the use of curse words, its not like anyone hasn't heard it the word before. I guess some people are just born with a stick up their ass

[Tetra84]

I can't figure out what's so dangerous here - besides the ozone? I want to know WHY I shouldn't try this at home!

[bradley]

just for kobe bryan here

"I think Popsci was wrong to have that language. What intelligent person would use a four letter word anyway"

i do believe have, that, what, four, and word are four letter words too....seriously tho, its a video, and they cursed. i just watched it at my "christian" school with my teacher. he didn't like it but was WAY more interested in the video than the subtitles

[bradley]

and is it ozone or NO2