While eagerly anticipating my red-hot chicken wings to finish reheating, I heard a distinctive popping noise coming from my kitchen. As I ran back into the kitchen, I quickly located the source of this startling sound. The microwave! After rushing toward the kitchen appliance, I couldn’t help but notice the mesmerizing flashes of light from within. It was at that moment I realized that I had left the aluminum foil on the plate. Whether you’ve had this experience yourself or not, you’ve probably been told not to leave metal in the microwave. But have you ever wondered why?
How do microwaves work?
In order to answer this question, we should first explore the mechanism behind microwaves. Microwaves heat food using electromagnetic waves; radio waves to be precise. A magnetron generates these waves, converting electrical energy into waves around 12cm in length. These waves bounce around inside the microwave and are absorbed by polar molecules in the food. As the molecules absorb this energy, they become excited and vibrate. As a result, the molecules and in turn the food become heated.
Then why are metals and microwaves so incompatible?
To start off, metals reflect microwaves instead of absorbing them, causing the waves to repeatedly bounce around within the appliance. This usually occurs with more rounded objects with no protruding edges. Consequently, the reflecting energy can hit the magnetron, causing it to overheat and ultimately breaking it.
Another potential issue is the tendency for electrons to repel. For metal objects that have pointed edges, electrons can cluster at these edges and cause the object to become charged. However, the electrons are mutually repelled due to their like charges, and want to increase the distance between them. This can lead to arcing, where beams of electrons seemingly shoot out from the metal objects. This phenomena explains why sparks appear in the microwave.
Although it might seem tempting to skip the extra step and simply reheat leftovers in metal packaging, this can have many unintended consequences. From creating arcs of energy to potentially breaking your microwave, these issues are much more trouble than they’re worth. Next time you’re about to blast last night’s leftovers, remember to remove all metals from your food! Otherwise, you might end up with more than you can chew.