The simple answer to this question might surprise you, but it is actually safe to use aluminum foil in a microwave!
The full answer to this question is a little more complicated though, and requires you to follow a number of precautions if you want to use this material safely.
In this guide I’ll explain everything you need to know about the process.
First things first though, it’s important to understand a little about both aluminum foil and your microwave.
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- Microwaving Styrofoam – Important information you need to know before microwaving your takeout leftovers.
What Is Aluminum Foil?
Aluminum is one of the most commonly used kitchen materials, and is frequently used in cookware. This is thanks to its excellent ability to both conduct and retain heat.
The material is also reasonably strong, lightweight and easy to mold too. This makes it attractive to manufacturers, and popular with home cooks.
What about aluminum foil though? This stuff is equally versatile, and is frequently used for covering leftovers, wrapping over food so it retains its heat, and cooking meals in the oven.
None of us thinks twice about throwing a sheet of foil in the oven, but what about the microwave?
How Do Microwaves Work?
In very simple terms, microwaves work by generating waves which agitate the water molecules in your food. This heat is then conducted throughout the food..
Any metal you place in a microwave reflects all of these waves, which is why metal containers are no good for heating food this way.
Bouncing all that energy back into the walls of your microwave is also an excellent way to kill your appliance!
IMPORTANT: Before proceeding further, check the owner’s manual for your microwave. It may offer specific guidance about working with aluminum foil. Follow that advice!
What Happens If You Microwave Aluminum Foil?
If the walls of your microwave are made of metal, why is it bad to microwave aluminum foil in particular?
It all comes down to the thickness of the metal.
The sides of your microwave are fairly substantial, and are capable of tolerating the electric fields that flow through them.
For thinner metals like aluminum foil though, it’s a different story!
The current can quickly overwhelm the more fragile foil, heating it up ferociously fast, and potentially causing it to ignite.
If there are any wrinkles in the foil – creating sharp edges – the electrical current can create a spark. If there’s anything flammable near those sparks…you get the picture.
Can You Put Aluminum Foil In A Microwave?
There are two things to watch out for here.
First, make sure you check the packaging of your aluminum foil. If the manufacturer says it’s microwave-safe, then you’re good to go.
Just make sure you follow the guidelines in the next section for more detail.
Equally important though is to check if the manufacturer explicitly states it is not microwave-safe. In that case don’t use it, regardless of any precautions you might take!
How To Microwave Aluminum Foil
Is it safe to use aluminum foil in the microwave?
According to the USDA, it is possible to do so safely, but you need to follow some very specific precautions:
#1 Only Use Small Pieces Of Aluminum Foil
Microwaves can’t pass through metal, and are instead absorbed by the food. If you cover the entire dish in aluminum foil, the food just won’t heat properly.
That presents its own risks, of course.
You can, however, use very small pieces of aluminum foil to shield parts of the food.
If there are areas you want to prevent overheating, you can apply a little smooth foil there.
#2 Don’t Use Old Or Scrunched Up Foil
I mentioned the risk of creating sparks from sharp edges further up the page.
For this reason, it’s essential to use completely new, entirely smooth aluminum foil.
Do so and you won’t have to worry about generating those sparks.
#3 Shape The Foil Around The Food
When you apply the aluminum foil, do so in such a way that you shape it around the food.
This will reduce the risk of creating problematic sharp edges.
#4 Make Some Space Between The Foil & The Oven Wall
Leave at least one inch of clearance space between the top and sides of the microwave, and the aluminum foil you’ve applied.
Just as importantly, if your microwave has a metal turntable or metal shelves, don’t use aluminum foil at all.
#5 Pay Attention!
This isn’t the kind of job you want to set and forget while you get on with other chores.
Keep a close eye on the microwave while it’s in operation. If you see any sparks, shut it down immediately and remove the foil.
#6 Less Is More
If you must use aluminum foil in your microwave, keep the portions small.
This reduces the risk of the foil coming into contact with the tops and sides of the microwave, and especially as the turntable moves around and jostles the contents.
Can You Microwave Foil Trays & Containers?
That’s aluminum foil covered, then, but are aluminum foil pans microwave safe?
The answer to this depends entirely on what the manufacturer says.
Check the packaging first. If you no longer have the packaging, it’s much better to stay on the safe side and avoid heating it in the microwave
Even if your aluminum foil pans are advertised as microwave safe, don’t use them after they’ve become bent or warped.
This again increases the risk of generating sparks.
In terms of heating the food well, it’s important to only use shallow trays that are around 1-2 inches deep.
The heat will only be able to reach the food through the top layer. If the foil tray is too deep, the bottom section of the food won’t be cooked properly, before the top part becomes dry and overdone.
Wrapping Up
Having read all of that, you may well be wondering if the benefits of using aluminum foil in the microwave are worth the risks!
If you’re prepared to use just a small amount of foil and keep an eye on proceedings, I think it’s fine to do this occasionally.
Just remember to follow the USDA guidance I’ve outlined in this guide, use new smooth foil, and use it sparingly.
Mark’s a lifelong food fanatic and spent ten years working as an entertainment journalist. He now combines his love of food, drink and writing as the founder and editor of Viva Flavor. Read more