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11 comments

Grapes on Fire

Posted August 11, 2016 10:10 AM by Chelsey H

Working at a boarding school, the most common reason the fire alarm goes off is a microwave incident (usually burnt popcorn). We all know that there are some things you shouldn’t put in the microwave – any kind of metal, most plastic containers, and Styrofoam.

But did you know that you shouldn’t microwave grapes?

In an experiment done in the video here. A grape is cut almost in half, covered with glass, and microwaved. After just a second you can start to see huge sparks coming from the grape in the microwave. What’s happening is that the two sides of the grape are acting as a focal point for the microwaves. As the microwaves move across the grape through the piece of skin left uncut, this tiny part of the grape skin quickly dies out and burns up, causing a spark. Image Credit

The spark ionizes the air around the grape, creating an ion-rich gas known as plasma. Plasma is one of the four fundamental states of matter which can be created by heating a gas or subjecting it to a strong electromagnetic field. This decreases the number of electrons, creating positive or negative charged particles called ions.

The sparks are big because the plasma conducts the electricity and can absorb the microwaves. The more it absorbs, the bigger it gets. The glass contains the air around the grape even more for a better light show.

A warning – this experiment can cause burn marks in your microwave.

While I don’t recommend experimenting with things in your microwave – if you have a microwave story, please share with us below! Have you ever microwaved a grape? What about ivory soap?

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#1

Re: Grapes on Fire

08/11/2016 12:56 PM

Someday, I'll buy an old microwave to experiment with. I'm afraid using the kitchen microwave for experiments might lead to a significant decrease in domestic tranquility.

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#6
In reply to #1

Re: Grapes on Fire

08/12/2016 1:52 PM

Grapes of Wrath?

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#7
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Re: Grapes on Fire

08/12/2016 2:05 PM

What kinds of foods do librarians bring to a potluck?

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#8
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Re: Grapes on Fire

08/12/2016 4:56 PM

Probably bookworms.

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#10
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Re: Grapes on Fire

08/12/2016 5:06 PM

Volumes and volumes of food?

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#11
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Re: Grapes on Fire

08/12/2016 5:10 PM

Stacks and stacks of condensed volumes of Reader's Digestible foods?

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#2

Re: Grapes on Fire

08/12/2016 3:56 AM

Chocolate kisses can be made HUGE as the air in the mixture warms and expands. I have heard that they will also catch fire if "overdone"!!

Grapes are full of sugar (inflammable!), so it does not surprise me that they react to microwave energy badly....

What idiot wants a hot grape anyway?

Perhaps he misread "Hot Grope?"

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#4
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Re: Grapes on Fire

08/12/2016 9:55 AM

I still remember when I found out 'flammable' and 'inflammable' meant the same thing. Sheesh.

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#5
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Re: Grapes on Fire

08/12/2016 12:02 PM

Is that a typo, or do the British use inflammable for something that can ignite? I remember in high school our English teacher said that no company in the USA ever put "inflammable" on a gasoline tank or truck. I went out and found one labeled this way, and photographed it for her enlightenment. So that has been used in the USA as well.

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#3

Re: Grapes on Fire

08/12/2016 7:31 AM

I've had cooked (deli) ham arc in the microwave, from all of the edges. Didn't seem to harm the rest of the ham though so I ate it after cutting away the charred edges.

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#9

Re: Grapes on Fire

08/12/2016 4:59 PM

OMG - you induced an imbalance in the aether, by tempting the incredible energy density of the cosmos with a grape and a few tiny waves. Did you check the result with a geiger counter? Elemental analysis before and after? NDE?

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