If you have ever witnessed something like miniature lightning in your microwave, it’s because you put something metal in it. But metals and the microwave have a complicated relationship. What kind of metal can you microwave?
Can you put stainless steel in the microwave? It is safest not to put stainless steel in the microwave, as metal reflects microwaves instead of absorbing them. This can cause sparking and is a fire hazard. This is especially true if the metal is formed into complex shapes like forks or if there is more than one piece of metal present.
In this article, you will learn why putting stainless steel in the microwave is a hazard and why, in a few cases, it isn’t, provided you take the right precautions.
Microwaves and Metal – What’s the Deal?
Before we go into detail about why you can or cannot put stainless steel in the microwave, it is important to know how this extremely helpful appliance works.
How Do Microwaves Work?
Microwaves, as a type of radiation, fall between the categories of radio and infrared waves. These waves are absorbed by most foods, which makes it possible to heat them within seconds.
The atomic motion that these waves create in food causes it to heat evenly.
A microwave oven will heat your food unevenly only when it doesn’t manage to get waves to the center of the food, be it a large piece of meat or a pile of leftover pasta with sauce.
Taking a minute to evenly distribute the food on the plate will solve the problem.
The waves are absorbed by fat, sugar, and water in food. There is a common misconception that microwaves cook food from the inside out, but this is simply not the case.
If it were, you wouldn’t end up with a Hot Pocket that’s face-melting hot on the outside and a block of ice in the center.
Microwaves actually heat by causing loose molecules in the food to rotate, creating energy from friction, which becomes heat. That heat is then distributed evenly through convection.
The misconception stems from the fact that this process warms the inside of foods much faster than an oven without the edges getting browned or burnt.
What Happens When You Put Metal in the Microwave?
Now that you know how a microwave works, understanding the complicated relationship between microwave ovens and metal will be much easier.
As we have already mentioned, microwaves are absorbed by fat, sugar, and water. They are not absorbed by neutral materials such as plastic, ceramic, or glass. Metal, on the other hand, is on the other end of the spectrum.
When you put metal in the oven, it reflects the waves, just as it reflects light.
Microwaves cannot penetrate the dense cloud of electrons in the metal, so instead, these electrons are charged up and electrical currents build up on the surface which are then released in sparks.
Is It Ever Okay to Put Metal in the Microwave?
You may have heard that metal in the microwave is a big ‘no’. While this is true and the safest route, there are a select few cases when putting metal in the microwave is okay.
Moreover, many microwave meals come in packaging that contains a metal piece or is made with a thin foil layer.
This thin metallic layer in food packaging, such as microwave pizza, is there for a purpose; it gets very hot and reflects heat evenly through the food.
And, you’ve probably noticed that there is metal in the microwave oven itself. The inside walls of the microwave, as well as the mesh on the door, are made from metal. They are there to keep the waves inside the oven.
So how does it happen that certain kinds of metals in the microwave are safe and even helpful, while others may cause your kitchen to burn down if you are not cautious enough?
Metal You Can Put in the Microwave
Whether you can put metal in the microwave or not depends not so much on the type of metal, but its shape and surface.
A thin piece of tin or steel that lays flat in the microwave and doesn’t touch the sides of the microwave may not cause any sparks. Even then, it is important to keep an eye on it and not let it cook for too long.
A metal pan, however, will. Its four walls, no matter how short, will continually bounce the waves back and forth, eventually sparking and setting your food ablaze.
Why Shape Matters
You may have left a spoon in your dinner while reheating it and have not experienced any sparking. But that has not been the case with a fork. Why is that?
The reason why forks spark in the microwave while spoons don’t is that forks have sharp edges and corners. The waves cause the charged particles to move to the corners of the fork. They form an arc that creates the sparking.
As the shape of the spoon is smoother and it doesn’t have sharp edges, putting it in the microwave is safer.
In any case, you should certainly avoid putting such metal objects in the microwave as forks, spoons, or knives.
Plates with a metallic trim are one of those items that you should not put in a microwave too.
It may damage not only your dish but the microwave oven itself. The metallic part of the plate will overheat under the waves and form an electric arc.
Why Timing Is Important
Even with metal sheets that you can put in the microwave, you shouldn’t do so for too long.
If you have accidentally left a spoon in your oatmeal while reheating it for 30 seconds, you are not likely to set your oven on fire.
Keeping metal in the microwave for as short as possible is important if you don’t want it to spark.
Microwaving Stainless Steel
Stainless steel, which is regular steel covered with a thin layer of chromium, is not different from other types of metal when it comes to putting it in the microwave. It reflects the waves the way other metals do.
A small flat piece of stainless steel, if used correctly, is unlikely to cause sparking in the microwave. A stainless steel pan or a fork, on the other hand, certainly will.
Additionally, if you put a stainless steel object too close to the metal walls of the microwave, it may cause major sparking, damage to your microwave, or even a fire.
Stainless steel is a common material used in the making of travel mugs. Don’t try to microwave these types of mugs.
Not only will your drink remain cold as a result of the shield the metal creates, but it will also damage your magic kitchen appliance.
Putting Metal in the Microwave – What You Should Know
If you are not going to read this section through, the only thing you should take away is that it is better to not put metal in the microwave if you are not sure it is safe.
If you want to do it the right way, read the directions. This refers to not only the instructions of the device you are using but also to the food you are heating if the latter refers to products that come in some type of packaging.
First of all, the manual that comes with your appliance will set the primary rules to follow. It is important to learn what you can and cannot put in the microwave.
Last but not least, follow the USDA guidelines any time you are unsure about the safety of microwaving a certain material.
What’s Up With Aluminum Foil?
Aluminum foil and the microwave may raise a lot of questions.
On one hand, you are often advised to heat food in aluminum foil. On the other hand, you may have seen videos of aluminum foil melting or sparking in the microwave. How is this explained?
If you put a ball of crinkled aluminum foil in the microwave, you will see lots of sparking. This happens because of the sharp edges and complicated shapes of the foil. The foil may even melt because of the high heat conducted through it.
It is not advisable to put foil in the microwave, but you can do it safely if you follow the right steps.
Here are the guidelines for using foil in the microwave according to the USDA:
- Wrinkled foil can cause sparks, so only use a sheet of new, smooth foil.
- If the microwave oven already has metal shelves or a metal turntable, do not use any more metal in your microwave.
- Lay the sheet flat beneath your food or otherwise only cover up to 1/4 of the food with foil.
- If you wrap part of your food, shape the foil carefully and smooth the edges so that there are no angles or edges sticking out.
- Make sure the foil is at least 1 inch away from the walls of the microwave.
- If you see any sparks, stop microwaving immediately and transfer your food to a microwave-safe dish.
The key is using a small amount and making sure you have not left any sharp edges.
You shouldn’t cover the food with aluminum foil entirely. As metal doesn’t absorb the waves but reflects them, your food will remain cold. Not only that, but your microwave may suffer damage too.
Thus, foil can be used to cover certain parts of food if you want to avoid overcooking.
If you want to wrap your food in something that will help it stay together, retain its moisture, and heat evenly, we suggest wax paper instead.
Can You Still Use A Microwave After Putting Metal in It?
If you have witnessed small sparks in your microwave after heating metal in it, your microwave will most likely still function properly.
So long as the appliance is in good shape and hasn’t caught fire or suffered any damage, there should be no risks.
With this being said, even if you manage to get away with heating metal in the microwave and have your appliance properly functioning, make it a habit to not leave metal utensils or cookware in your microwave.