Can you put Aluminum Foil in a Microwave?

When I was a kid, my favorite thing to eat was non frosted pop tarts. I remember getting up one morning, opening a pack of pop tarts, and placing the whole thing in the microwave. The next thing I know I see sparks shooting in the microwave. My mom quickly ran over and opened the microwave, and boy was she upset.

Can you put Aluminum Foil in a microwave? Yes, you can but should not put aluminum foil in a microwave. Putting foil in a microwave can cause arcs (sparks), smoke, and a fire. The sharp edges of aluminum foil is what can cause the sparks, smoke, and fire.

Continue reading to see why you can’t, what happens if you do, and other things you shouldn’t put in a microwave. 

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Why you can’t put foil in a microwave?

Time to get technical!

The reason you cannot put aluminum foil in the microwave is aluminum foil is a thin piece of metal that gets very hot as microwave currents pass through them. The inside of a microwave is basically a metal box that bounces microwaves back and forth. These waves are absorbed by food and once absorbed, convert into heat. 

Because aluminum foil is thin, it isn’t able to reflect microwaves, and can’t covert it to heat like food. The result is that aluminum foil becomes very hot and that’s when the sparks fly. Depending on the the amount of foil, and the wattage of your microwave, the sparks can happen quickly, or not at all. 

What happens if you put aluminum foil in the microwave?

The strange thing about putting aluminum in a microwave is either this combination will result in sparks or fire, or nothing at all. As I mentioned, there are a few variables that can have an impact on what happens after you put aluminum in the microwave an press start. 

Aluminum foil with sharp edges has a higher chance of creating a spark. For some reason, aluminum foil with parts that come to a point has a better chance of starting a spark than aluminum foil with smooth edges. The problem with that is aluminum foil seems to crumple the second you touch it.

Also, the higher the wattage, in combination with aluminum foil, the higher the chance for something to happen. As I discuss in this post, microwave wattage is the amount of energy flowing in a direction. The higher the wattage number, the more energy being create and flowed in a direction. 

In this instance, energy turns in to heat, and every element has a melting point. For example, 1,500 watts converts to 1,112-degrees Fahrenheit (572-degrees Celsius). In addition, Aluminium melts at 1,221-degrees Fahrenheit. With these two number in mind, it is easy to see how sparks can fly and fires can get started with Aluminium foil. 

What else can’t you place in a microwave?

Here is a short list of other things you cannot put in a microwave:

  • Paper bags/ cardboard – these items can catch fire if placed in a microwave.
  • Metal – as mentioned above, metals with a sharp edge can create a hazard in your kitchen
  • Any plastics, not labeled microwave safe – these plastics can fold under the pressure and melt, or explode. 
  • Styrofoam – harmful for the environment, and harmful for you, just don’t do it.
  • Stainless steel – This steel is good for the exterior of the microwave, not the interior. 
  • Empty microwave – empty microwaves can catch fire because the microwaves aren’t being absorbed. 
  • Clothes – Elastic can melt under the microwave heat. In addition, melted elastic combined with highly flammable cotton can result in a fire in your microwave
  • Kitchen sponges – putting a sponge in a microwave does not kill bacteria, and a dry sponge can create sparks and a fire. 
  • Plates with metallic trim – just like the metals mentioned before, this is not a good idea. 
  • Cold storage containers
  • Newspapers
  • twist ties

What can you put in the microwave?

Now that we know what you can’t put in a microwave, lets take a quick look at what you can put in a microwave:

  • Microwave safe containers – microwave safe containers mean they won’t melt when you microwave them. The containers and the contents of the microwave can still be very hot.
  • Glass – great for liquids
  • Ceramic dishes – great for reheating cold pizza
  • Paper plates – great for reheating just about anything
  • Paper towels – good for covering your food to prevent splatter
  • Napkins – also good for preventing splatter
  • Wax paper – good for covering your food and drinks
  • Parchment paper – good for covering your food and drinks
  • Wood or straw baskets
  • Heavy plastic wrap

How to test if something is microwave safe?

Here is a quick test to see if something is microwave safe:

  • Place the item to be tested and one cup of tap water into a microwave
  • Make sure neither the item nor the cup of water is touching the microwave sides
  • Microwave the item and tap water on high for one minute.
  • If the item tested is warm to the touch, it not considered microwave safe. 

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Why you can’t put aluminum foil in an oven but not a microwave?

The main difference between microwaves and ovens are the ways in which the heat is created. Ovens generate heat from a slow build up from fire or another source. As mentioned above, microwaves generate microwave currents and bounce back and forth in the metal box. 

The easiest way to think of it is ovens heat the air to a temperature, while microwaves create heat in the items in the microwave box.

Aluminum Foil cooking rules

According to the United States Department of Agriculture (USDA) here are a few rules if you need to cook with aluminum foil in the microwave. 

Use new, smooth foil only. Wrinkled foil can cause arching (sparks)

Cover no more than 1/4 of the food with foil

Shape the foil smoothly to the food so no edges stick out

It makes no difference which side of the foil (shiny or dull) is facing out

Do not place the foil closer than one inch from the oven walls

If the microwave oven has metal shelves OR a metal turntable, don’t microwave food in foil containers or metal pans, and don’t let foil used for shielding touch or be close to the shelves or turntable

If you see arching (sparks), immediately remove the foil shielding; transfer frozen food from foil container to a microwave-safe utensil

How to properly cook food in a microwave?

You should follow these steps to properly cook food in the microwave:

  • Place food in a microwave save-container
  • Cover food with a microwave safe lid. This will help cook food evenly, and hold in the moisture
  • Cook foods until they reach the desired temperature
  • Check the temperature in a variety of places for evenness and doneness. 


So it turns out that you can place Aluminium foil in at microwave. However, in order to do so, you must follow very strict conditions. First, you cannot have any edges. Edges can result in sparks and sparks can lead to fires. Second, You can only cover a very small portion of your food with foil. It makes you wonder if it’s even worth it.

Third, make sure the foil doesn’t touch any walls. Because the inside of a microwave is basically a metal box, foil that touches the sides can quickly create an arc. Fourth, if there are already metals (metal turntable, metal shelves) the foil cannot touch these things easier. 

It is much easier to tell people they cannot use foil in microwaves, instead of asking them to follow a step by step guide to warm up their food in two minutes. 

Have you tried putting aluminum foil in a microwave? What happened? What happened to the food? What happened to the microwave? What else did you try and put in a microwave with poor results? 

Cleave a comment below!

Additional questions

Can you break a microwave by putting metal in it?

This depends on the metal, how long it was in the microwave, and how old the microwave is. As I mentioned in the opening paragraph, I put a pop tart wrapper in a microwave, sparks flew after a few seconds, and my mom opened the door.

The next morning I followed my same routine. This time I removed the pop tarts from the wrapper and placed them on a paper towel. I successfully microwaved my pop tarts for 30 seconds. In fact, I don’t remember ever replacing that microwave until we moved from that house 15 years later.

Also, a microwave older than 9.5 years, is near the end of its lifecycle, and cooking metal may push it over the edge. 

Is microwave safe plastic really safe?

When something is “microwave safe” it means that it is rated to handle the high temperatures of a microwave. In addition, microwave-safe plastic won’t melt or break apart. Microwave safe does not mean it is safe for the environment or safe for humans.

Which plastic is microwave safe?

Plastic number 5 (#5) – Polypropylene is rated as microwave save. 

Are all Tupperware products microwave save?

As long as they are marked #5, they are microwave safe. Refer to the Tupperware website for exact products.