The simple answer to this question may surprise you, but aluminum foil is actually safe to use in a microwave!
But the full answer to that question is a little more complicated, and there are precautions you need to follow if you want to use the material safely.
In this guide, I explain everything you need to know about the process.
How Microwaves Work
Microwaves work by generating radio waves that cause water molecules in the food to spin and heat as a result of friction. The conductive properties of a food or liquid transfer heat to the center of the food.
Metal reflects these microwaves. That’s why a microwave is basically a big, secure metal box, so you don’t have to cook everything in the room around you. If you put a thick piece of metal in a microwave (like, say, a pot pie pot), the microwave will just bounce back and forth between the pot and the wall of the microwave.
However, thin pieces of metal like aluminum foil cannot withstand the energy provided by microwaves and will quickly heat up and ignite. The electromagnetic field in the microwave causes an electric current to flow through a foil, and if the foil is crimped into sharp edges, the electric current will discharge as a bright spark.
What Is Aluminum Foil?
Aluminum foil, commonly known as the silver sheet of plastic grocery packaging, can be used for many different purposes. It can store leftovers, cover hot dishes to keep them warm, and can be used in cooking and baking. This is thanks to its excellent thermal and insulation capabilities.
The material is also fairly strong, lightweight, and easy to shape. That makes it attractive to manufacturers and popular with home cooks.
How Do You Know If Aluminum Foil Is Microwave Safe Or Not?
There are several ways to determine if you can heat aluminum foil products in the microwave.
First, read your microwave oven user’s manual to see if there’s a statement about not heating aluminum foil. Some microwaves (such as those with metal turntables) cannot be used for this capacity.
Next, read the box for the aluminum foil product, or check the bottom of the actual product. If you don’t see any claims about microwave safety, it’s best not to put it in the microwave.
(Even if you don’t see anything about microwave heating aluminum foil, it’s fine if you follow the instructions above).
Finally, contact the manufacturer directly. You can ask if any aluminum is microwave safe and even double-check with the company that made it.
What Happens If You Microwave Aluminum Foil?
If the walls of your microwave are made of metal, why is microwave aluminum especially bad?
It all depends on the thickness of the metal.
The sides of microwave ovens are strong enough to withstand the electric field that flows through them.
But for thinner metals like aluminum foil, it’s a different story!
The current quickly overwhelms the more fragile foil, heating it up quickly and potentially causing it to ignite.
If there are any wrinkles in the foil, forming sharp edges, the electric current will create sparks. If there’s anything near the spark.
How To Microwave Aluminum Foil
- Use a new smooth foil. Wrinkled foil can cause electric arcs (sparks).
- Leave at least an inch of space between the top and sides of the microwave, and between the aluminum foil you use.
- Cover no more than a quarter of the food with foil.
- If the microwave has a metal shelf or turntable, do not use aluminum foil containers or metal pans to microwave food, and do not allow shielded aluminum foil to touch or near the shelf or turntable.
- Apply the foil smoothly to the food so that no edges protrude.
- If you must use aluminum foil in the microwave, keep it small. This reduces the risk of foil coming into contact with the top and sides of the microwave, especially when the turntable moves and bumps into the contents. Microwaves cannot pass through metal but are absorbed by food. If you cover the entire plate with aluminum foil, the food won’t heat properly.
- Foil it makes no difference which side (bright or dim) of material faces outward.
- When the microwave oven is working, please pay close attention. If you see any sparks, close and remove the foil immediately.
After reading this, you might be wondering if the benefits of using aluminum foil in your microwave are worth the risk!
If you’re prepared to use only a small amount of foil and keep an eye on the procedure, I think it’s ok to do it occasionally.
Please remember to follow my guidelines for using new smooth foils and use them with caution.