11 Things You Should Never Put in the Microwave

This appliance is super-handy — but it can't handle everything.

Getty + Dana Tepper


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Dry Sponges

If you like to zap the bacteria that lingers on your kitchen sponge in the microwave, you need to make sure the sponge saturated with water first. Here's why: Microwaves are attracted to water. "They work by making water or fat molecules move and heat by friction," explains Sharon Franke, director of the Kitchen Appliances and Technology Lab at the Good Housekeeping Institute. "If sponges are dry, there's no water to attract energy and the sponges themselves will attract energy and can catch on fire."

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Food Containers With Metal

Stop before you heat up last night's Chinese food leftovers if the containers have metal handles, to be specific. You see, metal is more solid than food, so as the microwave heats up, molecules in the material start to vibrate, but don't have anywhere to go — which could start a fire. Just move your rice and veggies to a plate to avoid this mishap.

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Eggs With the Shell

Do not try to hard-boil eggs in your microwave. When the shells are intact, the steam has no where to go, so the egg could end up exploding when it gets too hot. But don't worry: You can cook already-cracked eggs in your microwave.

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Since foil blocks microwave energy, it's generally not a good tool to use in the microwave. However, Franke says small pieces can be used to shield corners or sections of food that you don't want to overcook — just make sure it's smooth. Crumpled foil is the problem: the bends and arcs between points and cause sparking. Your best bet? Refer to your owner's manual before using this material.

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Herbs for Drying

Want to speed up the process of drying a bunch of herbs after buying too much? Whatever you do, don't put it in the microwave. Franke discourages this since the herbs don't have a lot moisture in them — so, if dried for too long, these plants can catch on fire. However, already-dried herbs used to season a dish are fair game.

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Plastic Containers

Unless your tub is deemed "microwave safe" by the manufacturer, these containers could degrade and become pitted when heating up foods with a high fat content in the microwave, according to Franke. But if you forget, it's generally not harmful to your health. When the GH Institute tested heating food in plastic, our tests found "there was no migration of chemicals into food after microwaving."

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Vintage Tableware

Since the FDA didn't establish limits on leachable lead in tableware until over 40 years ago, some vintage dishes might contain the stuff. And if your plates show signs of deterioration or cracking, it could mean the glaze is disintegrating, which could allow lead to leach to the food. To be safe, avoid heating up food in vintage bowls, cups, or plates.

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Brown Paper Grocery Bags

The USDA says these bags from your local supermarket are "...not sanitary, may cause a fire, and may emit toxic fumes" when heated.

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Travel Mugs

Many of the mugs people use to tote their morning cup of jo on their commute are actually made from stainless steel. So unless the manufacturer says they're "microwave safe," steer clear. If it's not safe, and you want to reheat the liquid inside, you'll have to transfer it to a new cup.

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Plates With Metallic Trims

While the glamorous trim on your wedding china might be what makes it special, you already know metal is a fire-starter in the microwave and chances are this trim fits into that category. Save your plates (and your appliance) by nuking dinner on a microwave-safe dish instead.

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Sure, it might be tempting to warm socks in this appliance before heading out of the house on a cold morning, but don't. Microwaving clothing could cause a fire, since there's no water for the appliance to pull energy from. Just stick with your clothes dryer instead.

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