What if I put aluminum foil in the microwave?

The microwave oven is one of the great inventions of the 20th century -- you can find them in millions of homes and offices around the world. At one time or another, we've all been told not to use metal products, especially aluminum foil, when cooking with a microwave oven. Stories of incredible explosions and fires usually surround these ominous warnings. Why is that? Let's take a look at how microwave ovens work to find out.

 

...Tiny sharp pieces and thin pieces of metal are a different story. The electric fields in microwaves cause currents of electricity to flow through metal. Substantial pieces of metal, like the walls of a microwave oven, can usually tolerate these currents without any problems. However, thin pieces of metal, like aluminum foil, are overwhelmed by these currents and heat up very quickly. So quickly in fact, that they can cause a fire. Plus, if the foil is crinkled so that it forms any sharp edges, the electrical current running through the foil will cause sparks. If these sparks hit something else in the oven, perhaps a piece of wax paper, you'll probably be reaching for the fire extinguisher...

 

Howstuffworks "What if I put aluminum foil in the microwave?