At one point or another, you’ve probably been told to never put aluminum foil in your microwave, unless you want to cause a fire. Does that rule live up to modern microwave standards, however, or is it just a myth? Here you’ll find the answers to those questions, so read on.

But first, to determine whether it’s okay to put tin foil in your microwave, we have to learn how microwave ovens work.

How Do Microwaves Work?

Microwave ovens are one of the greatest inventions of our era. They save us time, make cooking/heating up food more convenient, and take up very little space in comparison to regular ovens. However, as straightforward as they are to use, the mystery surrounding what you can and can’t put in them seems to remain.

Essentially, the oven produces microwaves (electromagnetic radiation) that get reflected by its metal interior and end up being absorbed by the food. They excite its molecules, which naturally produces heat, and voilà; you get the perfect mac ‘n’ cheese in a matter of minutes!

But here is the catch — as I’ve already mentioned, microwaves can’t pass through metals, and aluminum foil is made of almost 100% pure metal… I think by now it’s obvious why people have warned you not to put it in your microwave oven and…hope for the best.

But what could possibly go wrong?

What Happens When You Put a Wrinkled Ball of Aluminum Foil in the Microwave?

You might have heard of the notorious aluminum foil ball trend. It started as a joke — people were pretending that they could turn a crumpled ball of foil into a perfect reflective sphere just by placing it in the microwave for a few minutes. Needless to say, that goes against the laws of physics (and common sense), but still, there were thousands of people who decided to try it for themselves. Foreseeably, that resulted in a few broken microwave ovens and loads of disappointment

But for the sake of it, let’s pretend you decided not to listen to common sense and tried to follow the trend. What you would probably see are sparks (an arcing effect) and possibly flames.

That happens because the electric currents formed by the microwave oven overwhelm the foil (which, unlike the walls of the oven, can’t handle them). Consequently, it heats up immensely and forms sparks.

The thing some people find strange is that there are two usual outcomes of the tin foil experiment. You either see the whole flames and sparks flying around thing or nothing at all. That depends on several variables, like the voltage of your microwave, how much foil you’ve placed inside, and even how wrinkly it is (sharp edges usually have a greater chance of creating sparks).

Regardless, I’d say don’t try it at home, because you can actually ruin your microwave oven. There are plenty of videos on the internet, so if you’re curious, check them out; it’s safe and free…

Can You Put Other Aluminum Foil Items in the Microwave?

Now that we got the aluminum ball experiment out of the way, let’s see if the same rules apply to all kinds of objects made of this material. Spoiler alert — they don’t.

According to the United States Department of Agriculture (USDA), you can put small amounts of tin foil in the microwave to use as a shield on some parts of the food (e.g., poultry drumsticks and wings), which you do not want to overcook.

However, the USDA also recommends checking the owner’s manual of your microwave just in case.

In addition, some food that has been packaged in tin foil containers can also be microwaved. Again, that depends on the specific oven you have, so read the instructions. But generally, there shouldn’t be a problem. The aluminum baking trays in which you receive your takeout food, for example, are safe to microwave.

Just be extremely careful because, sometimes, the tray will actually remain cold, while the food inside it will be steaming hot.

Rules for Safe Use of Aluminum Foil in a Microwave Oven

Now that you know aluminum foil can cause a fire in some cases and be perfectly safe to use in other, you’re probably asking yourself, How can I be sure my microwave won’t randomly explode because of my tacos wrapped in foil? To help you, here are the points the USDA makes for safe use of foil in the microwave, as well as some additional tips worth mentioning.

Use a new, smooth sheet of foil for each dish you want to microwave.

You can probably guess why the notorious trend with the wrinkled ball of foil was so foolish. All the sharp edges, which are very hard to avoid, can cause sparks.

Do not cover more than 25% of the food with foil.

As you already know, microwaves bounce back from metals. If you completely cover your food in foil, it simply won’t heat up. Therefore, try to only cover areas that may burn.

If you’re heating up meat, for example, you can use wooden toothpicks to hold thin strips of foil over the thinner parts. Thus, you can comfortably let the thicker portions get nice and warm without drying out/burning the thinner ones.

As you gain some experience, you’ll know exactly how much foil you need, depending on the dish you’re heating up.

Make sure you shape the foil to the food.

This one should be pretty obvious, considering that edges that stick out cause sparks. Take the extra time to make sure everything is nice and smooth before you toss it in your microwave oven. 

It does not matter which side of the foil (shiny or dull) is facing out.

Some people debate whether they should use the shiny or dull side of their aluminum foil. Well, the USDA says it doesn’t matter. The difference in the appearance of the two sides actually comes from the manufacturing process and has nothing to do with the efficiency of the foil.

Only use shallow foil containers.

Microwaves have their limitations. They can penetrate through food, but only a few inches deep. The rest of the cooking happens by conduction.

If your tray is more than three inches deep, you risk getting the top of your food heated while the bottom remains cold. Then, you’ll have to put it in for another round, and by the time everything is heated up, the top is overcooked or even burned.

To avoid that, simply use shallow foil containers.

Place the foil in the center of the plate, making sure it does not touch the oven walls.

The metal walls of your microwave oven are there to reflect the microwaves and keep you safe from them. Yes, microwaves are harmful to live organisms. But don’t worry; if your oven is working properly, there shouldn’t be any problems.

If there are pieces of foil that can come in contact with the sides, however, quickly fold and smooth them out. You don’t want them to rub against the walls while rotating, as that could cause some issues (like sparks).

If your microwave has a metal turntable, don’t place aluminum foil or any other metal objects in it.

Again, you should avoid contact between two metals at all costs. Some people suggest placing another object in between (e.g., a glass or ceramic plate beneath the tin foil tray), but the USDA advises against the use of aluminum in such cases altogether.

Check your manufacturer’s recommendations just in case, though. They might have come up with a different solution.

If you see sparks, remove the foil tray/shielding immediately.

There is always some room for error. That’s why I’d say don’t take your chances, and remove the foil shielding you’ve created if you spot sparks/flames. The same rule applies to foil containers that cause such problems. Simply transfer your food to a microwave-safe container.

Sparks May Form Regardless of the Use of Aluminum Foil

Some foods are also prone to creating sparks. Those include dense vegetables, like raw carrots, spinach, beans, etc., and even hot dogs. In the case of veggies, the reason for the arcing is the rich mineral content. Hot dogs, on the other hand, can have unevenly mixed additives and salts, which could cause sparks in the microwave.

Whatever the reason, if you spot anything wrong, immediately remove the contents of your microwave oven. When caught early, sparks should not cause any problems, but if left alone, they can damage the oven.

To Sum Up

There are many dos and don’ts when it comes to using aluminum foil in the microwave. As a rule of thumb, never place a ball of foil (or any other shape you’ve made) in your oven. That’s dangerous and could cause accidents.

Food in aluminum trays can be heated up in a microwave unless the contrary is stated by the manufacturer.

I hope this article managed to shed some light on the rather controversial “no tin foil in the microwave” topic. Stay safe and bon appétit!

Related post: Can You Put Aluminum Foil in a Regular Oven?

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