Nine things to never put in the microwave

bowl of vegetables cooking in microwave

A microwave is a handy appliance to have in the kitchen. It’s perfect for heating up leftovers when you have no time or desire to cook a proper meal. And it can be a lifesaver when it comes to softening butter and melting chocolate when you’re baking something in a limited time. But they definitely aren’t designed to heat everything you can fit through the door.

Some things can be harmful to your health, and some can even catch on fire. Here are nine things you should never put in the microwave.


Plastic food containers
Microwaves are great for heating up leftovers that you’ve stored in Tupperware, or similar containers, overnight but it’s a bad idea to heat food in plastic.

The main concern with microwaving plastic is that it can cause harmful additives to leach into your foods.

The primary chemicals of concern are bisphenol A (BPA) and a class of chemicals called phthalates, both of which are used to increase the flexibility and durability of plastic.

These chemicals – especially BPA – disrupt your body’s hormones and have been linked to obesity, diabetes, and reproductive harm.

BPA is found mostly in polycarbonate (PC) plastics, which have been widely used since the 1960s to make food storage containers, drinking glasses, and baby bottles.

Note that even if a plastic container is labelled ‘microwave safe’, that simply means it won’t melt.

To be on the safe side, transfer the food to a microwave-safe ceramic or glass dish.

Read: Scientists sound alarm over microplastics in common food

Brown paper bags
This is a tricky one as a quick google search about making your own microwave popcorn in a paper bag will bring up hundreds of results claiming it’s the best thing since sliced bread.

It may seem like a safe material to heat up – they’re made of paper just like a paper plate, after all, but they can be harmful and dangerous.

Many paper bags are made from recycled products, which can contain ignitable particles such as metal flecks that can cause sparks and even ignite the paper.

Paper bags can also emit toxic fumes when heated. Glue is required to produce a bag with a square bottom and some even have ink printed on them. Both of these things can produce toxins when heated and can contaminate the food inside.

Aluminium foil
This one’s pretty obvious as you should keep anything metal away from the microwave, but seeing as it’s one of the most commonly used kitchen helpers it deserves to be on the list.

It’s essentially a very thin metal that, when exposed to microwave radiation, will reflect the energy instead of absorbing it. This, in turn, can create sparks that could ruin the appliance, or worse, start a fire.

Read: Nine things you probably didn’t know you could use your microwave for

Travel mugs and thermos cups
It might be tempting to pop your cooled coffee in the microwave after a long, cold morning out but most travel mugs and thermos cups aren’t microwave safe.

If it’s made from stainless steel, don’t nuke it. The stainless steel will block the heat from warming your coffee or tea and can damage your microwave. The item will directly say whether it can be used in the microwave or not.

You’d be surprised by how many people are still reheating their leftovers in polystyrene containers. But polystyrene is a type of plastic and doesn’t handle well in the microwave.

One key reason is that it contains a compound called styrene, which human and animal studies have linked to cancer.

In addition, when foods or beverages are microwaved in containers made from polystyrene or plastic, substances used in manufacturing may leak into the food, especially when heating fatty foods, such as meats and cheeses.


Hot peppers
Raw peppers likely won’t explode in the microwave. However, they do contain a compound known as capsaicin that vaporises at high temperatures. The fumes can be highly dangerous if exposed to your eyes or breathed in, and you’ll likely get a hit of it when you open the microwave door.

It’s a process similar to making pepper spray, so keep that in mind before popping those peppers in your microwave.

You may have seen the news of people being severely burnt by trying to poach or hard boil eggs in the microwave and having them explode into their eyes when they open the door.

The rapid heat from the microwave creates a lot of steam in the egg, either in the shell or in the unbroken yolk. This steam has nowhere to go so it can cause the egg to explode. If you manage to get away without any burns, you’ll probably have a big mess to clean up.

Read: How to clean your oven and microwave naturally

If a recipe ever calls for warm grapes, avoid putting them in the microwave. Grape flesh is sealed in tight skin, microwaving them creates a lot of steam inside that has nowhere to go. You’ll be left with a mess at a minimum, or a fire in the worst-case scenario.

This goes for raisins too; they won’t explode but they will quickly start smoking.

Anything saucy without a lid
Well, this one’s just going to make a mess.

Where to place food in the microwave
The most common problem people have with the microwave is getting food to cook evenly. The solution? Maximising the reach of those electromagnetic waves.

We know that microwaves create heat by vibrating water, sugar and fat molecules. We know microwaves are short, and that microwave ovens tend to have hot spots and cold spots. Knowing this, we can arrange the food in a way that ensures an even distribution of heat.

So, instead of keeping food piled in the centre, spread it in a circle around the outer edge of the container or plate. The more you spread it out, the better. This makes it easier for the microwaves to reach in and create enough friction to heat the food evenly.

Have you ever had a microwave disaster? Do you have a microwave at home? Let us know in the comments section below.

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