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10 things you should never put in your microwave

We reveal the items that you should avoid heating up in your microwave and why, plus what to do instead

10 things you should never put in your microwave

After a long day, sometimes a quick, hassle-free microwave dinner may seem like the best option. But it’s worth knowing that there are some things you should never cook this way.

According to our 2019 reliability survey, one of the most common reasons microwave owners had to buy a new model was complete breakdown of the old one.

To put off microwave shopping for as long as possible, there are a few things you can do to prolong the life of your existing model.

This includes being careful with what you choose to heat up, as some items can do more damage than you might realise.

In the market for a new microwave and want to know which models we recommend? Take a look at our pick of the best microwaves for 2020.

1. Hard-boiled eggs

Popping a raw egg in the microwave to cook may seem like an effective shortcut to a hard-boiled egg, but it’s definitely not a good idea.

The high temperatures used by microwaves can create an extreme build up of steam inside eggs, to the point where they can explode – regardless of whether they’re shelled or unshelled.

Sometimes they’ll explode during cooking, creating a horrendous sticky (and smelly) mess on every interior surface of your microwave, but they could also burst after you’ve removed them, scalding your hands or mouth.

What to do instead

The safest way to cook a hard-boiled egg is the old-fashioned way – on your hob in a saucepan of boiling water.

Check out our best hobs guide to find out which ones will make a perfect hard-boiled egg.

2. Chilli peppers

Microwaving a chilli pepper won’t cause any unexpected explosions, but it certainly won’t be a pleasant experience.

If you choose to heat one up in your microwave, you’ll release large amounts of capaiscin, the chemical that makes chilli peppers spicy.

When you open the microwave door to take them out, the chemicals will be released into the air, which could potentially lead to an unpleasant faceful of pure spicy heat and streaming eyes.

What to do instead

Literally anything else. Most types of pepper can be roasted, grilled, pan-fried or enjoyed raw, depending on the dish you’re making.

Make sure to always thoroughly wash your hands after handling chilli peppers to avoid capsaicin irritating your skin, mouth or eyes.

3. Leafy greens

Blasting your kale or spinach in the microwave might seem like a speedy shortcut to a nutritious dinner, but could be potentially dangerous.

Leafy greens need a bit of moisture to cook, so popping dry vegetables in the microwave could lead to them sparking and potentially starting a fire.

At best, you could end up with a slightly singed dinner, but at worst, you risk permanently damaging your microwave.

What to do instead

The most common way to cook leafy veg is steaming or boiling. If you like your greens with a little more crunch, they can also be stir-fried or sautéed.

If you absolutely have to use your microwave, be sure to rinse your veg under running water before placing them in a microwave-safe container sealed with cling film or a well-fitting lid, so they get gently steam cooked.

4. Rice

According to the UK Food Standards Agency, you shouldn’t reheat home-cooked rice in the microwave as it may contain a type of bacteria called Bacillus cereus, which isn’t killed during the cooking process.

If you were to eat any rice that still contained this bacteria, you could potentially get food poisoning.

What to do instead

The safest way to cook dry rice is in a saucepan of boiling water on the hob, following the instructions on the packet.

If it’s not possible to serve your rice as soon as it’s been cooked, you should try to cool it for an hour and store it in the fridge for no longer than 24 hours.


Make sure you pick a tried-and-tested model that has been proven to cook evenly and effectively in our independent tests – use our microwave reviews


5. Tomato-based sauces

As tempting as it may be to pop your chopped tomatoes, passata or pasta sauce into the microwave to heat them up quickly, you should avoid taking shortcuts with these types of sauces.

They are usually too thick to allow heat and steam to escape, meaning this build up in the sauce during cooking before exploding, making a mess of the inside of your microwave.

The trapped steam could also cause air pockets to develop in your sauce that don’t burst until you remove it from the microwave, risking spattered clothes or even scalding.

What to do instead

Tomato-based pasta sauce will taste best if you reheat it in a saucepan on medium heat, adding a splash of water if the sauce has thickened while in the fridge.

If you do reheat it in the microwave, add a little water to thin it and don’t over-do the time or power level. A simple vented food cover will help to prevent splatters covering the interior.

6. Water

If you don’t feel like waiting for the kettle to boil, it may seem like a good idea to pop your mug of water straight into the microwave for a speedy cup of tea or coffee.

This isn’t a good idea, though. A cup of water doesn’t have anything in it to diffuse the energy from the microwave, causing it to ‘superheat’. This means that while it won’t boil, it could still be extremely hot and potentially dangerous.

If you were to remove a hot cup of water from your microwave and add something to it (such as a tea bag or a spoonful of sugar), you could inadvertently cause it to explode.

What to do instead

The best way to make a hot drink is with a kettle or, failing that, a pan of boiling water.

Take a look at our Best Buy kettle reviews to see which models performed best in our rigorous tests.

7. Paper bags

Some people may be shocked to see this one in here, especially if you’re a fan of microwave popcorn, but conventional brown paper bags should never go in your microwave.

Popcorn bags are lined with a special material that works to consume the radio waves produced by your microwave, making them safe to use.

The paper bags you buy in the supermarket can release dangerous fumes when warmed up. Some could even catch fire inside your microwave if they heat up too quickly.

What to do instead

If you’re craving popcorn, simply swap out the brown paper bag for a microwave-safe bowl and you’re good to go. Add the popcorn kernels, oil and salt or sugar before covering the bowl with a vented lid, and heating on ‘high’ until the popping sounds stop.

It’s also fun to do this one on the hob with a clear-lidded saucepan.

8. Styrofoam

While Styrofoam containers are a great way of protecting food in your fridge or freezer, they aren’t suitable for the microwave.

Heating Styrofoam in your microwave can cause it to lose its shape or even appear to melt. The most common issue, though, is that the heat produced by the food you’re cooking could begin to melt the Styrofoam container and ruin your dinner.

What to do instead

Check what type of Styrofoam you’re using. One type is microwave-safe, so you’re good to go, but the other type isn’t.

If you’d rather err on the side of caution, simply transfer your food or drink to a glass, ceramic or microwave-safe container before heating it up.

9. Wheat bags

Although wheat bags are designed to be heated safely in your microwave, you need to make sure you follow the heating and usage instructions to the letter. If not, you risk the bag overheating and igniting.

To heat up a wheat bag safely, you need to thoroughly clean your microwave, removing any grease or food splatters that could cause potential hotspots. You should also only heat it for the specified time, even if it doesn’t feel hot enough.

Bear in mind that some microwave brands advise against using wheat bags and doing so can invalidate your warranty.

What to do instead

While wheat bag manufacturers are under no legal obligation to adhere to safety regulations, there is a voluntary regulation in place – look out for the safety standard BS 8433:2004 when purchasing.

This means the product you buy will have undergone a flammability test and there will be usage instructions permanently attached to the wheat bag.

When you come to use the wheat bag, make sure you follow the instructions to the letter and discard the product if you have any concerns.

Alternatively, opt for a traditional hot water bottle with a cover.

10. Nothing at all

It may sound silly, but it can be easy to do – if you stopped it before the timer ran out for example – and turning on your microwave without anything inside it is a no-no.

When you hit ‘start’ on an empty microwave, the radio waves that would usually cook your food get redirected back into the machine. This will damage your microwave over time, causing it to stop heating effectively.

While in most cases this will just mean you need a new microwave, the worst-case scenarios could result in an electrical fire and cause a lot more damage.

What to do instead

Always double check your microwave is completely turned off when removing food or drink and keep an eye on it when you close the door to make sure it doesn’t start running again.

If you’re unsure whether or not your microwave is defective, always contact the manufacturer before using it again.

For more tips, head to our guide on getting the most out of your microwave.

Buying a new microwave

Microwaves can last an age, but if yours is getting a bit old, slow or rusty round the edges, it could be time for a replacement.

Things to consider are:

  • Cooking functions Do you want a model that can also grill and oven-cook food, or just to be able to quickly reheat or defrost things? Basic microwaves are cheaper, but a combination model could give you more cooking options.
  • Capacity The smallest models can squeeze a plate of around 27cm inside, whereas the roomiest can manage 35cm dishes. Flatbed microwaves have no turntable, so you can use awkward-shaped tubs too.
  • Worktop space Some models take up a lot of kitchen space, particularly the pricier combination models. Others need a decent amount of clearance between them and the wall or cabinets, so you’ll need to ensure you’ve got a suitable space that’s also near a plug socket.

Check our full microwave buying guide for more advice, or head straight to our microwave reviews to find the best for your budget.

We’ve tested all the latest models, from cheap own-brand offerings for less than £40 to premium combi models that can cook and grill food too.

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