Is it safe to put aluminum foil in the microwave? The answer might surprise you.
In terms of kitchen tools, aluminum foil is surprisingly useful and quite inexpensive. But what about when you want to heat up some foil-wrapped leftovers or make foil-packet dinners on the go? Can you put aluminum foil in the microwave?
Technically yes. But it requires taking safety precautions (and using good judgment). (Learn more about whether you can microwave cardboard.)
Is it safe to use aluminum foil in the microwave?
Microwaves are very convenient because they use high-powered radio waves to cook food quickly. They do this through radiation, which is also how we feel the heat of the sun. They use the shortest radio waves, which are full of energy, and send them into food. The interior of microwaves is reflective, which allows radio waves to bounce back and travel through food, causing the molecules within the food to vibrate. The faster they vibrate, the more the food heats up.
Radio waves have a frequency where water, fats, and sugar can absorb them, but some plastics, glass, and ceramics can’t (so you can microwave them without burning yourself in the container).
Meanwhile, the metal is reflective, causing radio waves to bounce back without giving the food a chance to heat up. But what about aluminum foil? It is thinner, which means it can be overwhelmed by microwave currents and catch fire.
But if you follow certain safety precautions, you can put aluminum foil in the microwave.
- Make sure the foil is smooth, not wrinkled.
- Use only new aluminum foil in the microwave; new aluminum foil will be wrinkle-free, reducing the risk of fire.
- Keep a distance (preferably at least 1 inch) between the aluminum foil and the walls and ceiling of the microwave; to ensure this distance is maintained, use smaller plates.
- Do not put aluminum cookware, such as pie pans, cake pans, and loaf pans, in the microwave. It is not safe and your food will not cook (the metal will reflect the waves instead of letting the food absorb them).
What about microwaving other leftovers? Check out our guide to microwave takeout containers.
What happens to aluminum foil in the microwave?
What happens to food in the microwave may not be the same with metal, especially aluminum foil. The problem lies not in the typical thickness of aluminum foil, but in that the metal is like a mirror in the microwave, which prevents your food from absorbing the microwaves.
Therefore, since they do not get hot at all, foods that are completely covered with aluminum foil should not be placed in the microwave. But that’s not the reason we’re told it’s dangerous to microwave with aluminum foil.
Microwaving aluminum foil will create an electrical field that neither the internal microwave circuitry nor the foil can tolerate. When your food is completely wrapped in aluminum foil, the currents of electricity produced by the microwave cannot be absorbed.
Those electrical currents will keep bouncing off each other and create massive heat that can burn the foil or the internal circuitry of the microwave. However, there is an even greater risk of microwaving aluminum foil, especially crumpled foil.
In reality, some of the electrical currents will not be reflected but will continue to move around the sheet. At the sharp corners or edges of the sheet, these electrons accumulate in extreme numbers, bounce off their neighbors, and then begin to arc.
Although aluminum foil is noted for its superb heat resistance, if those arcs hit something else that’s flammable, you face a high risk of explosion.
How to avoid the risk of using aluminum foil in the microwave?
So the above section is theory, but you can still find recipes from professional chefs that call for aluminum foil and can be cooked in the microwave. I bet the information will confuse you.
In fact, you can still use aluminum foil in the microwave, but with a few must-have notes. Since aluminum works like a mirror for microwaves, a small piece of aluminum foil can be used as a “shield” in the microwave
Just like when you wrap the tops of poultry thighs to prevent them from overcooking or burning, aluminum foil can be the same solution, with even better results in the microwave.
Be aware, however, that this could affect whether the aluminum foil can go through the recycling process, especially if there is too much food and grease stuck to the foil afterwards.
To use that trick, as well as other microwave foil cooking methods, here are some notes you won’t want to miss.
Tips for Microwaving Aluminum Foil
- There is some debate as to whether the shiny or dull side of the aluminum foil should face up. The brighter side should be able to reflect more radio waves, right? Not quite. The difference between the reflectivity of both sides is so minimal that it doesn’t really matter which side is facing up.
- Look for a microwave-safe label, and a label that explicitly says not microwave-safe (for example, some microwave-safe pizzas include a thin sheet of aluminum foil on the bottom, which helps crisp the crust). .
- If your microwave has a metal turntable or metal shelves, do not use aluminum foil.
- Cover only 1/4 of your food with aluminum foil to reduce the risk of fire and fully heat your food. Because aluminum foil will reflect radio waves, if it covers the entire food, it won’t get hot.
When it comes to microwaves, it’s always better to play it safe. If in any doubt, toss any leftovers into a microwave-safe bowl. In the meantime, we’ll make some of these delicious microwave meals for dinner.