Things to never put in the microwave

Microwaves. Those fantastic appliances that we use to reheat pizza or left overs, quickly zap that cup of tea or coffee you forgot about, or to quickly whip up some sides for your dinner. There are some commonly understood items we know to keep away from the turn table however there are also some pretty surprising items and foods (yes, foods) that shouldn’t be popped in and zapped. While some may seem self-explanatory, you’ll be surprised by what people will try. If you want to keep that microwave spick-and-span – stay away from putting these things in the microwave and prevent a microwave mishap!


You’ve probably heard this one plenty of times – but have you still made the mistake? Maybe popped in a mug with aluminium bits on it without thinking?

Here’s the reason behind why sparks fly when you heat up that metal. The heat bounces off the metal and prevents the contents from being warmed. The reflected waves also damage the microwave and create sparks due to a concentrated electric field.


While hot grapes may not sound too appetising, if you were considering giving this one a go – rethink it! When placed in the microwave grapes become tiny fruit-filled bombs. The moisture inside their skin steams and with nowhere for the steam to escape it explodes.


Paper Bags

Remove any items from their paper bags before heating them up. The radio waves emitted by the microwave can cause the paper to catch fire when heated, leading to your microwave bursting into flames!


Styrofoam is designed for single use and should only be used for holding food. Styrofoam is a type of plastic and it doesn’t play nice with heat. Microwaving these containers can cause its shape and structure to change, and as this happens harmful chemicals are released that then come in contact with your food.


Travel Mugs

While travel mugs are made for drinking beverages on the move, don’t stop by a microwave! Not all travel mugs are microwave safe; in fact, they’re usually made of plastic or steel. These cups are made to keep your drinks warm so the insulation prevents your drink from re-heating and it can possibly cause sparks.


Chillis (or hot peppers, to some) contain capsaicin, a compound that determines how spicy they are. When put in the microwave under high temperatures, chillis sweat it out and the capsaicin vaporises, which may cause you to choke and even burn your eyes. They won’t explode but they may spark and possibly cause a fire so stay clear of the fumes and keep the heat down!


Whole Eggs

Microwaves are designed to cook quickly. In fact, they work so fast that the eggs just can’t keep up. When a whole egg is heated in the microwave, steam develops inside the egg and builds up so rapidly that the egg explodes!

Cracked Dishes

Cracks in glasses, mugs or plates and other dishes can cause them to explode as the weakness in the crack will not be able to withstand the heat generated inside the microwave. So keep one eye peeled and regularly check your glassware and ceramics.



While we normally head for the kettle or the stove, if you come across the need to heat up water in the microwave, stop. A microwave can heat the water beyond its boiling point meaning that when you take it out of the microwave and add something to it, there’s a chance that it will explode and possibly burn you.


Your microwave is not a dryer! While it may not occur to you to head for the microwave with your wet clothes – some people will have tried it or at least considered it. If those socks are a bit damp or your fave shirt is wet but your housemate is using the dryer, the perfect and most obvious solution is the microwave, right?! Wrong. The microwave will heat up the water in the clothes, with some areas becoming so warm that they burn the clothes and cause a fire.


Vintage items

Do you collect vintage dinnerware? It may be time to check the dates on those items and test them with a lead testing kit as according to the Smithsonian, microwaving old plates and mugs that are over 40 years old can cause lead from glaze to seep into your food.

Plastic Bags and Containers

There are some myths out there that you shouldn’t heat up your food in plastic containers as you’re exposing yourself to cancer-causing chemicals called dioxins. The reality is that plastics don’t contain dioxins but rather, dioxins are created when garbage, plastics, metals, wood, and other materials are burned. As long as you don’t burn your food in a microwave, you aren’t exposing yourself to these dioxins.

While some plastics are microwave safe, others can leak BPA and phthalates when heated, contaminating the food. Never microwave food inside plastic bags and keep in mind that old, scratched, or cracked containers, or those that have been microwaved many times, may leach out more plasticisers so it’s important to check over your containers and always microwave with the lid ajar.

Mobile Phones

Here’s one that may be hard to believe: back when iOS8 rolled out, a fake ad for iOS 8’s “Wave” feature started bouncing around the web. The misinformation campaign claimed that you could use Wave to “quickly charge your device’s battery using any standard household microwave” for a minute and a half. We wish we were kidding, but we’re not. This led to a lot of household iPhones zapping. Never put electrical devices in the microwave!


Nothing at all

Starting your microwave without placing anything inside will severely damage your appliance and cause it to blow up! Without anything for the microwave to heat up, the waves released have nowhere to go, causing them to bounce off each other and be absorbed by the microwave itself.

Have you encountered an item that led to a microwave mishap? Let us know which items to be wary of in the comments below.


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  1. A careful One says:

    Always put your wheat or other thermal bag into the microwave with a small shallow bowl of water.
    Otherwise your wheat or the cloth can get singed or catch fire, because there’s almost no moisture in it, and microwaves NEED moisture to do their stuff.

  2. Robyn Sheehan says:

    Another item NOT to place in Microwaves are little tinned potatoes. They will explode in your mouth and burn. Cover baked beans as they will pop all over the place as will tinned mushrooms. Peas, beans and corn niblets are other foodstuffs that loves to explode all over the micro. Cover when heating. Take it from one who knows and made more work for myself by having to clean up the microwave.