Here is a situation that has happened to many of us. We put our food in the microwave to reheat it and then have the sinking realization that we have left a metal spoon in the bowl. At this point, you probably sprint over to your microwave to stop it as soon as possible. But what would actually happen if you just left it in there?
Most of the time, it is perfectly safe to run the microwave with a metal spoon in it since it has rounded edges. It turns out that it’s the shape of the implement that matters. Cutlery with pointed edges can reflect the electromagnetic waves back and forth, often resulting in arcing (sparks).
So, as long as your metal food-eating implements don’t have sharp edges or touch the sides of the microwave, you are probably OK. The rest of the article will dive deeper into why this is the case. I’ll also cover if any damage can occur to the microwave and if other types of metal, like aluminum foil, can be “cooked” in a microwave.
What Will Happen if You Put a Metal Spoon in the Microwave?
Most of the time, if you put a metal spoon in the microwave, nothing will happen. This is especially the case if it is put in with some food or liquid because the food absorbs the reflected electromagnetic waves.
However, if the metal spoon is touching the wall of the microwave (which is also made of metal), the electromagnetic waves can bounce back and forth between them.
This can excite the electrons in the metal to such a point that they begin arcing into the air, creating sparks. These sparks can also be created by metal that is very thin, has a rough edge, or has points on it (like a fork).
Why Does Metal Spark in the Microwave?
Microwaves contain a magnetron, which is a vacuum-filled tube surrounding a magnetic field. This field produces electromagnetic waves. These waves bounce around the inside of the microwave, and when they hit materials that are made mostly of water (as most food is), these waves are absorbed and converted into heat.
When the waves hit a metal object, they excite the electrons on the metal’s surface, which prevents them from getting absorbed, so they are reflected back off. With a rounded object, like a spoon, these electromagnetic waves are reflected back into the food.
The electromagnetic waves produced by the microwave are at a frequency that can be absorbed by food or water. They are also at a frequency that can excite the electrons on the surface of metal objects. The electrons begin moving around rapidly, and this blocks the electromagnetic waves being absorbed by the metal, so they are instead reflected back off.
If these reflected waves hit another piece of metal, they are reflected back. This creates a charge in the metal that can eventually reach a high enough voltage that it rips an electron molecule off into the air, creating a spark. This spark sucks the electromagnetic waves in, which can make it grow into a ball of fire.
Is a Sparking Microwave Dangerous?
While it can look very dramatic, most of the time, a sparking microwave is no danger to you at all. All of the energy is contained within the microwave, and it can’t escape to harm you.
It can, however, damage the microwave itself, so it is still worth stopping it if you see any sparks inside. In extreme cases, the sparks can burn holes into the microwave’s metal walls, or they can damage the micro-electricals inside. Either of these can make the microwave unusable and/or dangerous.
Why Is Some Metal OK in the Microwave?
While all metal will reflect electromagnetic waves, this doesn’t always have the potential to create sparks. If the metal is thick and has a rounded edge, it is unlikely to have any way of generating the sort of charge that can get high enough to create sparks.
On the other hand, if the metal has sharp edges, is very thin, or has points (like a fork), there is the chance that the surfaces could reflect the electromagnetic waves back and forth. So metal items such as spoons and rounded baking trays are generally OK, but items such as forks and knives generally aren’t.
Cool Fact: Sometimes, companies can use the conductive nature of metal to their advantage. Microwave foods like Hot Pockets and microwaveable popcorn are in containers that are lined with aluminum that reflects the electromagnetic waves directly back into the food. This allows the food to reach a higher temperature than the microwave alone would be able to achieve.
Does Metal in a Microwave Ruin It?
If there is no arcing and no sparks, metal in the microwave won’t do any damage at all. If there has been arcing and sparks, there is a possibility that the microwave could be damaged. If there was a lot of heat generated, this can burn holes in the microwave wall, burn out the magnetron, or generate a surge that damages the micro-electricals that control the microwave.
So your microwave may stop working altogether. There is also the potential that it could make the microwave unsafe by creating holes that the electromagnetic waves could leak out from.
Can I Use Aluminum Foil in a Microwave?
It is safe to use small amounts of aluminum foil in the microwave. Just make sure the foil is flat and not crumpled up, as the folds could generate arcing. Also, make sure that the food is not entirely covered. Foil won’t let any electromagnetic waves pass through, so the food won’t heat up.
If the foil is placed in the microwave on its own (i.e., without any food), this can also create arcing. This can also mean that a charge is generated by the foil that is high enough to damage the microwave.
You can place small amounts of foil on particular parts of the food that you don’t want to get overcooked.
Contrary to popular belief, it is usually safe to put a metal spoon in the microwave. As long as there is also food/liquid in there as well, there isn’t any other metal, and the spoon isn’t touching the metal sides of the microwave.
Metal objects with sharp edges or points can generate high enough charges to create sparks and can cause damage to the microwave, but these sparks aren’t a danger to you. So just watch where the metal object is positioned, and as long as the spoon is in some food or liquid (with no other metals), it should be fine to run a microwave without removing the spoon.
I hope this article has been helpful. Thanks for reading!
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