Eli5 aluminum foil


Why is it okay to put hot stuff in/on aluminum foil, but it doesn’t like being in a microwave?

In: 0

Because microwaves aren’t just heat. They work by shooting high power radio-waves that are tuned to heat up water into your food, which heats up the water in it, and that water then heats up everything else.

We don’t want metals in microwaves because that first step of shooting high powered radio waves can cause metals to have electric currents to flow. That can both heat them up way hotter than food usually is, and it can cause them to ignite and make a plasma in your microwave, which is bad.

It’s not about the heat, it’s about the electrical conductivity. Microwaves can cause electrical currents to flow through metallic objects. If you put metal into a microwave, it’ll create dangerous sparks.

Microwaves are radio waves and metal makes great antennas for receiving radio waves as electrical voltages, because metal is a very good conductor of electricity. Microwave ovens are very powerful so the voltages that can build up in the metal are very high and can cause sparks and mini-lightning inside. And while the metal is sucking up much of the power of the oven in this way, the food isn’t being heated properly.