List of Things You Shouldn't Microwave

Exploring the Limits of Your Microwave Oven


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CDs and DVDs

Microwaving a CD produces a shocking display.
Microwaving a CD produces a shocking display. The aluminum coating on the CD acts as an antennae for the microwave radiation, producing plasma and sparks. PiccoloNamek, Creative Commons License


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Microwaving grapes can start a fire.
Microwaving grapes can start a fire. janasworld, Getty Images

No, you don't get raisins if you microwave grapes. You get fire. Grapes are mostly water, so you'd think they would be okay. However, the roughly spherical shape of the grapes, combined with their waxy peel causes the microwaves to generate plasma. Basically, you get mini-plasma balls in your microwave. Sparks can jump from one grape to another or to the inner workings of your microwave. You could ruin the appliance.

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Toothpicks or Matches

Don't microwave matches.
Don't microwave matches. Sebastian Ritter

Standing up a toothpick or a match supplies the right geometry to produce plasma. As with grapes, the end result could be a fire or a damaged microwave. Actually, if you microwave matches, you're pretty much guaranteed that fire.

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Hot Peppers

Naga Jolokia peppers are extremely hot, with a heat of over one million Scoville units.
Naga Jolokia peppers are extremely hot, with a heat of over one million Scoville units. Gannon anjo, public domain

Do not be tempted to dry peppers using your microwave oven. Heating the pepper releases capsaicin into the air, which the microwave fan will disperse into the room and subsequently your eyes and lungs. There may be some value to this as a prank, since the risk to the microwave is minimal. Otherwise, it's one way to pepper spray yourself and family.

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Light Bulbs

Control the light with your hands.
You can control how much of the fluorescent bulb is lit by the plasma ball by sliding your hand down the fluorescent light. Anne Helmenstine (2013 Ig Nobel Prize Awards)

Why would anyone microwave a light bulb in the first place? The reason is because the energy emitted by the microwave illuminates the bulb. However, the bulbs also contain metal, so microwaving them generates sparks and unevenly heats the glass, typically breaking the bulb. Sparks and an explosion may result, so there is a good chance of ruining the microwave. If it's a fluorescent bulb, you'll release highly toxic vapors into the air, thus poisoning yourself. Do not microwave!

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Eggs in Their Shells

Do not microwave raw or hard boiled eggs in their shells.
Do not microwave raw or hard boiled eggs in their shells. Steve Lewis, Getty Images

It's perfectly fine to cook eggs in the microwave, provided they aren't still in their shells. Cooking an egg in its shell heats the egg faster than it can release pressure, making an egg-bomb. The best case scenario is a mess to clean up, but there is a strong possibility you'll blow the door off the microwave.

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Water, Sometimes

The boiling point of water is 100 degrees Celsius or 212 degrees Fahrenheit.
The boiling point of water is 100 degrees Celsius or 212 degrees Fahrenheit at 1 atmosphere of pressure (sea level). Jody Dole, Getty Images

You probably heat water in the microwave all the time. However, there is a significant risk of superheating water, which happens when the water gets hotter than its boiling point without actually boiling. When you disturb the water, it suddenly starts to boil, often explosively. People get burned every year, sometimes seriously, from superheating water in the microwave.

How can you avoid this? Ovens with a turntable prevent superheating by jarring the water enough that it should boil when it gets hot enough. Otherwise, don't heat water longer than necessary and avoid reheating water that you forgot about, since the air bubbles that help it to boil will have been driven off by the first go-round in the microwave.

More Things You Shouldn't Microwave

In addition to the specific items listed, there are general rules about objects you shouldn't microwave. Unless it's listed as microwave-safe, you shouldn't microwave a plastic container. Even if the container doesn't melt, toxic fumes could be released. It's best to avoid microwaving paper and cardboard because they could catch on fire and because they release toxins when heated. Don't microwave metal objects because they can cause sparks which can result in fire or damage to the appliance.