Can you use tin foil in a microwave? The short answer is yes, but carefully (or else this happens). Read on to know why.
How Microwaves Work
Microwaves work by generating radio waves that make the water molecules in food spin and heat up because of friction. The conductive properties of the food or liquid carries that heat to the center of the item.
Metal will reflect these microwaves. This is why a microwave is basically a big, secure, metal box – so you don’t cook everything in the room around you. If you put a thick piece of metal in the microwave (say, like a pot pie pan) then the microwaves are simply reflected back and forth between the pan and the walls of the microwave.
However, a thin sheet of metal like a strip of aluminum foil can’t withstand the energy provided by the microwaves and will rapidly heat up and ignite. The electromagnetic field in the microwave will cause a current to run through the foil, and if the foil is crinkled into sharp edges, the current will discharge as bright sparks.
So Foil is Always a No-No?
Actually, it can be safe to use small amounts of aluminum foil in a microwave oven.
No food completely covered by aluminum foil or in a covered metal pan should be put in a microwave oven because food wouldn’t be available to absorb the microwaves. This will damage the oven or even burn it. However, small pieces of aluminum foil can be used to “shield” areas of foods, such as poultry drumsticks and wings, to prevent overcooking.
Some food packaged in foil containers can be safe to microwave. Read the package heating instructions to see if the food manufacturer has specific recommendations for microwaving the product. Because food in these containers will only heat from the top, it’s best to microwave foods only 1-2 inches in depth so food near the bottom will be heated thoroughly before food on top dries and overcooks.
Tips for Using Foil in a Microwave Safely
- Use new, smooth foil only. Wrinkled foil can cause arcing (sparks).
- Cover no more than 1/4 of the food with foil.
- Shape the foil smoothly to the food so no edges stick out.
- It makes no difference which side of foil (shiny or dull) is facing out.
- Do not place the foil closer than one inch from the oven walls.
- If the microwave oven has metal shelves OR a metal turntable, don’t microwave food in foil containers or metal pans, and don’t let foil used for shielding touch or be close to the shelves or turntable.
- If you see arcing (sparks), immediately remove the foil shielding; transfer frozen food from foil container to a microwave-safe utensil.
Hope this helps!