What Should and Shouldnt I Microwave?

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Microwaves are either a total kitchen life-saver or dangerous radiation machines, depending on who you ask. In reality, they are great for certain purposes, but not for others. Here’s how to figure out what to microwave and what to skip.

Dear Lifehacker,
I heard it’s dangerous to microwave food in plastic containers or plastic wrap because of scary food-contaminating chemicals. Is that true? What other things are safe or unsafe to use in the microwave?

Signed,
Nervous Nuking

Dear Nervous,
The microwave is a powerful appliance, and with that power comes great potential for harm—things like sparks or explosions and, yes, possible chemicals leaching into your foods. Don’t worry, though, your microwave most likely won’t kill you. Just heed these recommendations for safe microwave cooking.

Containers

More often than not, you’re going to need to put your foods and drinks in something to microwave them. Here are the materials that work best as containers and the ones to avoid.

Do:

  • Glass containers. These are probably the best to use, since there’s zero debate about how safe they are in the microwave.
  • Most paper plates, towels and napkins. However, because some paper towels are made with plastics and some paper plates and cups are coated with plastic, National Sanitation Foundation (NSF) International recommends only using those products marked as microwave-safe.
  • Ceramics. Most ceramics made with properly formulated glazes are safe in the microwave, but according to the Today Show, we should be careful when dealing with ceramics made in China. “Because China does not adequately regulate the industry, some manufacturers are using glazes that contain high amounts of lead and arsenic — dangerous elements that can leach into foods when microwaved,” the article explains. Also, be warned: plates, mugs or other containers with metallic paint can also cause sparks.
  • Wax and parchment paper, as well as microwave cooking bags are deemed fine too, according to NSF International.

Don’t:

  • Aluminum foil. Technically, you can use foil in the microwave (fun fact: Hot Pockets microwaveable containers and similar foods have aluminum lining), but it might not be the wisest thing to do and will probably catch on fire.
  • Metal containers (e.g., canned foods in their cans), for the same reason above.
  • Brown paper bags from the grocery store. Per the USDA: “They are not sanitary, may cause a fire, and can emit toxic fumes. Intense heat may cause a bag to ignite, causing a fire in the oven…The ink, glue, and recycled materials in paper bags can emit toxic fumes when they are exposed to heat. Instead, use purchased oven cooking bags.”
  • One-time storage containers like take-out containers, margarine tubs, or yogurt containers. They probably don’t have a “microwave safe” label, so you shouldn’t risk it.
  • Plastic trash bags, garbage cans or film canisters. I had no idea people consider these cooking vessels, but nevertheless the University of Nebraska warns against using these items for microwave cooking

Debatable:

  • Plastics. This is the big one people fear cause cancer. Even BPA-free products leach hormone-like chemicals (although other research suggests it might not be as bad as previously thought). The jury’s still out, though, on the health implications of microwaving or dishwashing plastics. The Environmental Working Group advises against microwaving foods or drinks in any kind of plastic container at all. The FDA, however, approves containers for microwave use based on their measures of the chemicals leaching out; as Harvard Health reports: “The maximum allowable amount is 100–1,000 times less per pound of body weight than the amount shown to harm laboratory animals over a lifetime of use. Only containers that pass this test can display a microwave-safe icon, the words “microwave safe,” or words to the effect that they’re approved for use in microwave ovens.”
  • Styrofoam. Similarly, some Styrofoam products are marked “microwave safe,” but when in doubt, don’t microwave it.
  • If you do decide to microwave in plastic containers, just make sure they’re not cracked, old, or discolored. And when covering food with plastic wrap, make sure the plastic doesn’t touch the food.

Food and drinks

Interestingly enough, even microwaving certain foods can be hazardous to your health or cause accidents, although overall microwaving food is great and can even help certain foods retain more nutrients.

Do:

Don’t:

  • Grapes. Apparently they can burst into flames and turn into a glowing ball of plasma gas.
  • Eggs intact in their shells or boiled eggs. The problem here is that the pressure builds up in the sealed egg “container,” which can cause it to explode (even if the boiled egg is peeled). Best to pierce the egg in multiple spots before nuking.
  • Dried hot peppers. Apparently, the capsaicin chemical in peppers is volatile and can catch fire.

Caution:

  • Take care when boiling water in the microwave, because it can be “super-heated” and possibly explode. A chopstick or other stick in the cup would prevent this.
  • As with the eggs, cut or prick items that may be more likely to explode because of internal pressure, such as hot dogs, sausages and potatoes. Also make sure you vent any container so steam can escape.

Other objects

You probably already know most metals shouldn’t be put in the microwave unless you want sparks and a light show. The list of other things you shouldn’t put in the microwave is pretty long, but there are also some unusual, non-destructive ways to use your microwave.

Do:

  • Wet sponge, to disinfect it. Make sure you squeeze out the dishwashing soap first.
  • Potting soil, to sterilize it, especially good for starting seeds.
  • Dish towels in a zip lock bag for a DIY hot water bottle.
  • DIY heat bag (fill with rice, beans, etc.). You can also just fill a sock with these things.
  • Beauty products. Real Simple notes you can briefly warm up products like hot-oil conditioners, hot wax for removing hair, and even facial masks.
  • Water with lemon. It actually cleans your microwave.

Don’t:

  • Dry sponge, which can catch fire.
  • Pretty much anything that’s been done on the Is It a Good Idea to Microwave This? show. The microwave specialists tested hundreds of items, including talking greeting cards, firecrackers, spray paint, Pikachu (the doll) and a propane tank. These usually resulted in melting, flames, sparks and smoke.
  • Living things. Enough said.

Debatable:

  • Soap. Well, this is really only debatable if you don’t want to be amazed or waste a bar of soap.
  • CDs. Sometimes you might just want to see a light show or destroy a CD.

Enjoy,
Lifehacker

This story was originally published on 2/27/14 and was updated on 10/9/19 to provide more thorough and current information.

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