🍲What’s Safe to Put in a Microwave?

Man Looking At Fire Coming From Microwave Oven Photo: Getty Images

This week I’m interrogating experts about what you can microwave (and what you shouldn’t), including the usual suspects (metal and plastic) and some unusual ones (shelled eggs). Also in this issue: Why you should take your shoes off at the door, and what happens when an EV runs out of juice?


THE BIG STORY

‘In the Hot Seat’

Growing up, my mom had only two safety rules in the kitchen. One was to be careful when using the stove (that was pretty apparent even to my 7-year-old brain). The other was to never stick metal in the microwave, a rule I followed faithfully without ever fully understanding why.

Then came that fateful time a few years ago when I microwaved a bowl of food with a metal fork inside by mistake. Both the microwave and I survived my oversight, but the experience of watching sparks come roaring to life in my microwave was definitely a once-in-a-lifetime lesson, and once was more than enough.

You never want using your microwave to be like playing Russian roulette. So to help you operate your microwave safely, I asked CR experts and microwave manufacturers about the things you can microwave and the things you shouldn’t.

Get Smarter

Here’s the most important thing to know: Check the owner’s manual. I get it. We all like to skip that part, but if you want to ensure you’re not microwaving anything unsafe, it’s worth consulting the safety instructions you’ll find there. (And if you can’t find the original copy, you can look for it online.) You should also never stray too far from the microwave when it’s on

With that being said, here’s the verdict on some materials, from the potentially dangerous ones to the “well, it depends” to the ones that are generally safe.

💥 The “you might destroy your microwave” category:

Metal shouldn’t be microwaved because it could cause arcing (sparks inside the microwave) and potentially even a fire, says James Dickerson, PhD, CR’s chief scientific officer.

Some manufacturers say you can use small pieces of aluminum foil in the microwave, just make sure they don’t touch the walls. James disagrees, and says it’s better to avoid putting foil in altogether because it could still lead to arcing.

Sharp objects, even those that aren’t made of metal, such as a wooden toothpick, can also set sparks flying. And other materials that could be disastrous include grapes (some people on the internet have run experiments with them) and eggs in the shell. If you microwave grapes, it creates plasma, a highly energetic gas, which turns them into fireballs, while whole eggs could explode. 

🤔The “it’s complicated” category:

Plastic foam, in general, might be okay if you’re only heating it for a short time, such as 30 seconds for a cup of coffee, says Louis Nieves, senior product engineer at Panasonic Consumer Electronics, which makes microwaves. If you microwave it for too long, however, the foam could melt. It’s also not ideal to heat your food in plastic containers because leaching, the transfer or leaking of chemicals into your food, might occur.

Paper products are tricky because they could be made with components such as chemicals, wood pulp, and other binders, which may not be safe under microwave light exposure. Brown paper bags, for example, are a no-go because they might cause a fire, and paper cups should be avoided because they, too, might overheat and ignite. In general, you should microwave a paper product only if it’s specifically labeled microwave-safe, says Louis.

�The “play it safe” category:

Glass, ceramics, and stoneware are materials that are usually microwave-safe, James says. You should, however, look out for containers with narrow necks, such as syrup bottles, because if the liquid inside gets superheated, pressure can build up and lead to an explosion, says JL Lavina, senior manager of public relations at LG Electronics USA, which makes appliances including microwaves.


HOT-BUTTON ISSUE

Part of knowing which items are safe and unsafe to microwave is that you’re less likely to damage your microwave and shorten its life span. What are other ways you can make your microwave doesn’t meet a premature end?

Keep it clean. Leftover food bits may absorb the microwave’s energy the next time you turn it on and create hot spots that could damage the interior.

Be mindful of cooking times. If you accidentally set your microwave at 50:00 instead of 5:00, you are likely to damage the unit. (Plus, RIP to that poor food you just decimated.)

Don’t run it empty. With nothing inside the microwave, it can overheat quickly and cause burn marks in the interior. 

If you have an over-the-range (OTR) microwave, which is more of a hassle to replace than a countertop, follow these tips to ensure better longevity:

💨Turn on the microwave’s exhaust fan so that when you’re cooking on the range cooktop below the moisture rising from your pots and pans won’t collect as much on the electronics of your microwave, which could shorten its life span. You can also wipe away the moisture with a paper towel or soft cloth.

💧Degrease the grease filters. If the filters get too gunky, your microwave might run less efficiently and pose a fire hazard. Soak the filters in a sink filled with hot water and a degreasing dish detergent, or put them in a dishwasher if your owner’s manual says it’s safe to do so.

Check out more expert tips on how to extend the life span of your microwave. Or if you’re on the hunt for a new one, here are the best microwaves in 2022 rated by CR.


QUIZ

Full battery on smart phone

Illustration: Consumer Reports, Getty Images Illustration: Consumer Reports, Getty Images

If you’re streaming on your phone, which drains your batteries more: using the WiFi network or your data?  

(The answer is at the end.)


ASK US ANYTHING

There is a lot of interest in electric vehicles these days given the rise in gas prices. Listeners of CR’s “Talking Cars” podcast recently submitted questions to our auto experts about them. Here are a few fun ones

 ⚡ Q: Is there any type of break-in period for EVs, equivalent to the break-in procedures for vehicles with internal combustion engines?

There isn’t a break-in for an EV’s electric motor. But for the first 500 miles it’s best to drive not too aggressively so you can properly break in your tires and brakes, says CR auto writer Mike Monticello.

� Q: I’ve heard that cold weather decreases EV driving range. But what about EVs in hot climates, especially when using the AC?

EV range will be shortened by hot climates and AC, but it isn’t hurt as much as it’s in the cold, in part because a car’s AC is more energy-efficient than its heating system, says Jake Fisher, who runs testing at our 327-acre track. 

�Q: What happens the moment an EV runs out of juice? Does it stop in the middle of the road?

Your EV will give you plenty of warning. First, it will sound alarms and warning lights will appear to let you know the battery is running low. The car might also slow down as the battery loses power, says CR auto writer Keith Barry. When that happens, you’ll still have enough power to pull your car to the side of the road or to a safe spot before it stops dead.

Check out more expert responses to questions about EVs here. And if you have a question you want to ask an expert, email me. I’m all ears!


THE GOOD STUFF

Should you take off your shoes at the door?

@consumerreports Keep the nasty stuff 🦠 at the front door by doing this one tip from CR’s Nanoscience Expert James Dickerson. #science #cleantok #germs ♬ original sound - Consumer Reports

THE SHORT ANSWER

Are portable air conditioners more effective than a window AC? Eh, no.


RED ALERT

We asked our followers on Twitter and Instagram if they’ve ever put something in a microwave that turned out to be unsafe or dangerous, and a lot of you responded enthusiastically with your microwave mishaps.

The most common mistakes people have made are microwaving dishes with metal trim or heating food with aluminum foil. Someone even shared with us a picture of a scorch mark left in their microwave where the aluminum had come into contact with an interior wall. 

And then there are the wackier stories: A person confessed to microwaving a duck toy when they were 5. Another said he once tried to dry a pair of Air Jordan III 1988 in the microwave, which ended up destroying the shoes. A Twitter user shared that their fiancée once microwaved a bottle of maple syrup, which rattled around until it popped and spilled syrup in every place possible. (That must have been great fun cleaning up.)


QUIZ ANSWER

Performing data-intensive tasks over WiFi actually drains your battery way faster than using your cellular-data connection.


Smarter Owl Icon

"With great microwaves come great responsibility."



Headshot of CR Author Pang-Chieh (BJ) Ho

Pang-Chieh Ho

I'm a newsletter writer who likes looking into the different ways we can live smarter. The topics I cover typically explore unanswered questions we have about the products we use every day and bridge the gaps between what owners' manuals advise and what we actually do. In my spare time, I like to take photos, critique movies out loud while I watch (at home!), and take care of my ever-increasing plant "children."