Can You Put A Metal Bowl In The Microwave? [Solved]

Written By Patrick Hardi

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If you’re like most people, you probably have a few metal bowls lying around your kitchen. And also like most people, you’ve probably wondered if it’s safe to put a metal bowl in the microwave.

In this article, we’ll go over what is safe to put in the microwave and the science behind why some metal sparks in the microwave.

Can You Put A Metal Bowl In The Microwave?

The blanket answer is – You should never put anything made of steel, iron, copper, or other hard metals in your microwave. Metals can cause a fire when they’re heated in the microwave. However, some metals in small quantities might be safe for a microwave. And if you’re ever in doubt, it’s always better to err on the side of caution and just use a different bowl.

Anything made of or containing steel, iron, copper or other hard metals should never go in your microwave. 

Microwaves cause electric fields to flow through metal, resulting in extremely quick heating of thin pieces of metal like aluminum foil. This quick heating can cause ignition.

In general, you should only place plastic, glass, or ceramic containers, bowls, and other cookware in the microwave if it is specifically labeled as “Microwave Safe” on the container. Heating food in anything else in the microwave is risky. You should also check the owner’s manual for the manufacturer of the microwave to see what materials they deem as safe to microwave.

Why Does Metal Spark When Placed In The Microwave?

Electromagnetic waves cannot penetrate metals. Instead, they induce surface electrical currents in the metal. Where there is a bend in the metal, the electromagnetic fields are concentrated. The sharper the bend, the more the electromagnetic fields are contracted.

With very sharp corners, such as the tines of a fork or the edges of aluminum foil, the fields can become so concentrated that they strip electrons off of the molecules of the air, causing ionization of the air and the spark that you see.

How Are Microwave Walls Made of Metal?

If metal in the microwave is so dangerous, then why are the inside walls of the microwave made of metal? The walls of most microwave ovens are made of metal, and the windows can made of metal mesh. The mirrored walls of the microwave reflect the microwave radiation back into the food, ensuring even cooking.

It goes back to avoid thin pieces of metal with sharp edges. Many microwaves come equipped with a metal rack. If you examine the rack, you will notice that it does not have any sharp or pointy edges. This helps to avoid any potential electrical arc sources.


Have more questions about things you can do with a microwave? Check out this recent article Can You Microwave A Candle To Melt The Wax? for more common questions solved!


How Do You Know If a Bowl Is Microwave Safe?

The best way to tell if something is microwave safe is if it is clearly labeled as “Microwave Safe” on the dish. There is also a test you can do on a dish if it is not labeled to check if it is microwave safe. However, you must watch closely and stop the process at any moment if you see any smoke or sparks in the microwave.

The proposed test will help to identify whether a given dish is made of materials that absorb and retain heat, or if it instead allows heat to pass through. In order to carry out the test, you will need the dish in question and a cup or glass that is safe to use in a microwave.

  1. Step 1: Place a microwave-safe cup or glass filled with tap water in the microwave oven.
  2. Step 2: Place the dish in question next to the microwave-safe cup in the microwave.
  3. Turn on the microwave with both dishes inside for roughly one minute. Watch them closely to make sure no sparks occur.
  4. If the temperature is warm or hot, the microwave is not safe to use. If the temperature is cold and the cup of water is hot, then the dish is safe to use in the microwave.

Can You Put Aluminum Foil In The Microwave?

According to the USDA, aluminum foil can be used safely in small amounts in a microwave oven. Placing small pieces of foil over areas of food such as poultry drumsticks and wings can help prevent overcooking.

But aluminum foil can be easily overwhelmed by electrical currents in a microwave, causing them to heat up quickly and potentially start a fire. If the foil is crinkled so that it forms any sharp edges, the electrical current running through it can cause sparks.

If these sparks hit something else in the oven, such as wax paper, a fire may start. So, you must be very careful when using even small pieces of aluminum foil in the microwave. When it comes to microwaves, it is best to exercise caution and avoid placing any kind of metal inside.

What Can Go In The Microwave?

If you’re wonder