HomeKitchen13 Things You Should Never Put in a Microwave

13 Things You Should Never Put in a Microwave

When the microwave was first invented, I’m sure there were plenty of sceptics around, questioning its safety. 

Since then, we’ve learned that microwaves are indeed safe, not to mention absolute lifesavers when you need to quickly reheat a meal, make a mug cake, or even just rewarm your coffee. Whether you own a 900-watt or a 1100-watt microwave, you are likely very much appreciative of the service it provides.

However, there are items that you should definitely not put in your microwave. And some of them are not as obvious as others. 

Sure, we all know we shouldn’t put metal in a microwave. But do we know why? And do we understand the need to remove that delish takeout from the paper or styrofoam container it has arrived in before microwaving it? 

I’ve decided to do a bit of research into the things one should never pop into the microwave, and here’s what I’ve come up with.

Can You Put Styrofoam in the Microwave? 

Well – it depends. 

Styrofoam is actually a polystyrene foam that contains a compound called styrene (hence the name), which has been linked to cancer

When you microwave a styrofoam container with your meal in it, some of the substances used to make it can leak into your food, and well, you don’t actually want that. 

However, there are styrofoam containers specifically designed to be used in a microwave. You can be reasonably sure these won’t mess with the food you are about to eat. 

If you want to be on the safe side though, remove your takeout from the container it has arrived in and microwave it on a microwave-safe plate. 

After all, we’re never in all that much of a hurry to tuck into our food, are we?

Can You Put Glass in the Microwave ? 

Most likely. 

But do check the label to ensure the item is microwave-safe. Glass that isn’t may contain tiny bubbles of air that can expand as they are heated up, which will shatter your glass inside the microwave. 

Glass that is trimmed with metal is absolutely not microwave-safe. The metal will spark and shatter the glass, so don’t even try. 

Coloured glass may also not be microwave-safe, as the dye used to colour it may not be food safe, so make sure you check the label, once again. If you are unsure, use a different glass. 

Oh, and in case you were wondering, the microwave-safe label looks like a wave. Like this.

Can You Put Paper Plates in the Microwave ?

Most likely.

Plain white paper plates should be perfectly safe. Use two or three of them if the item you are microwaving is particularly greasy or cheesy (yes, I mean pizza), so that you prevent the oil from seeping through the paper. 

Printed or coloured paper plates may cause a fire though, or they may leak god knows what kinds of chemicals into the food, so don’t use those.

You can also use wax paper, or even plain paper towels or plain paper bags – provided that they are not made of recycled paper or that they are not coloured. Brown paper bags are a fire hazard, while recycled paper can contain chemicals that are not food-safe. 

You can cover your dish with a plain paper napkin to prevent spatter too – again, as long as it is white and not made of recycled materials.

Can You Put Plastic in the Microwave ? 

Honestly, I wouldn’t recommend it. 

Plastic, especially BPA-filled plastic, can cause plenty of harm. BPA is most often found in PC plastics that have previously been used to manufacture storage containers. Modern storage containers are BPA-free and made from PP plastic – but that does not mean the process of microwaving won’t cause some of the materials used to make your plastic container get into your food. 

There are plastic food containers on the market that are specifically labelled as microwave-safe. Yet, if you want to stay on the absolute safe side, use a plate instead of the plastic. Go for the paper kind even. 

Can You Put Cardboard in the Microwave ? 

In theory – but it might not be the best idea. 

Just like it’s safe to place paper plates in the microwave, cardboard should be equally okay. Never place cardboard in the microwave on its own though, as you also need the food in there that will absorb the waves. 

The food will heat up faster than the cardboard, as it contains more moisture. To be on the safe side though, only do short intervals and pause the process frequently to make sure the cardboard is not getting too hot.

However, you also want to consider the fact that cardboard is often made of recycled materials, and it might contain something that is not actually microwave-safe, or something that can mess with your food. 

Rather be safe than sorry, and go for that white paper plate if you need to – if you don’t have a regular plate at hand, that is.

Can You Put Ziploc Bags in the Microwave ?

If it says so on the bag, yes. 

If it doesn’t, definitely not. 

Most Ziploc bags will be labelled as microwave-safe, and they will be intended for defrosting and reheating in a microwave. You need to stick to the temperatures and procedures recommended by the manufacturer though. 

However, if you have purchased a cheap knockoff and have ziploc bags lying around that are made by who knows what company, and they don’t have a label that clearly indicates they can be used in a microwave, I’d skip them.

Can You Put Aluminium Foil in the Microwave ?


Yes, you will find articles online that tell you it’s safe. Yes, you probably use aluminium foil in the oven and find it’s perfectly safe. 

However, the thin foil, once placed in the microwave, will heat up incredibly quickly, and it can cause a fire. If the foil is also crinkled, it can cause sparks that may damage your microwave, or set something inside on fire. 

Rather than testing your microwave’s abilities and playing with fire, forego the aluminium in the microwave experiment, and reheat your meal in a safer way. 

Can You Put Metal in the Microwave? 

Absolutely not

The metal you put in your microwave will heat up quickly. Unlike your food, it contains no moisture which would heat up, release steam, and be ready to eat. Metal will simply catch on fire. 

Metal items can also reflect the microwaves as opposed to absorbing them, and reflect them back to the metal on the microwave’s walls. Which will then bounce back onto that same metal, and keep bouncing in circles until the microwave overheats and suffers some proper damage. 

Be smart – don’t put metal in your microwave.

Foods Not to Put in the Microwave

Now that we’ve covered all the basics, I also want to address some food items you shouldn’t be microwaving. 


If you want to turn your microwave into a complete mess, just try throwing some grapes in. 

Their thin skin will rupture super fast, and they will end up all over the microwave. If you are particularly unlucky, they will also catch on fire.


Spinach is full of iron, which is why it’s so good for us. However, when reheating spinach, the iron may oxidize, generating free radicals that can cause cancer or infertility.

Try to eat all of your spinach in one sitting – otherwise, you are much better off throwing it out than reheating it.


Reheating mushrooms will generate oxidized nitrogen and free radicals which will mess with your digestive system. 

If you insist on storing them for a subsequent meal, eat them cold. 

Raw or Whole Eggs 

Reheating cooked eggs is another bad idea, and for the same reason. Foods that are high in protein contain lots of nitrogen, and rehearing them will cause it to oxidize, which can again result in cancer.

Also refrain from placing a whole raw egg into the microwave – it’s more than likely it will burst, as the heat can’t escape the shell fast enough.


Accidentally turning the microwave on for a second or two while it’s empty won’t do too much harm. However, letting it run empty will ultimately damage it, as the microwaves aren’t absorbed and just keep bouncing off the walls. 

Ready to Give up on Your Microwave? 

Please don’t! 

A microwave is an incredibly useful appliance, and there are so many great models available on the market you will surely find one that suits your needs perfectly. 

Just because you have to plate your takeaway doesn’t mean you should give up on this time-saving gadget. 

Not to mention, it’s great for making mug cakes. 



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