Can You Put Aluminum Foil in the Microwave?
Is it safe to put aluminum foil in the microwave? The answer might surprise you.
In terms of kitchen tools, aluminum foil is surprisingly useful and pretty inexpensive. But what about when you want to heat up some foil-wrapped leftovers or make foil-packet dinners on the fly? Can you put aluminum foil in the microwave?
Technically, yes. But it requires taking safety precautions (and using good judgment). (Learn more about whether you can microwave cardboard.)
Is It Safe to Microwave Foil?
Microwaves are so convenient because they use high-powered radio waves to cook food quickly. They do this through radiation—which is also how we feel the heat of the sun. They use the shortest radio waves, which are filled with energy, and blast these into food. The insides of microwaves are reflective, allowing the radio waves to bounce around and travel through the food, causing the molecules inside the food to vibrate. The faster they vibrate, the more the food heats.
The radio waves are at a frequency where water, fats and sugar can absorb them—but some plastics, glass and ceramics don’t (which is why you can put them in the microwave without burning yourself on the container).
Metal, meanwhile, is reflective, causing the radio waves to bounce off without giving the food a chance to heat up. But what about aluminum foil? It’s thinner, which means it can be overwhelmed by the microwave currents and catch on fire.
But if you follow certain safety precautions, you can put aluminum foil in the microwave.
- Make sure the foil is smooth, not wrinkled.
- Use only new foil in the microwave—fresh foil won’t have any wrinkles, which reduces the risk of fire.
- Keep distance (preferably at least 1 inch) between the foil and the microwave’s walls and ceiling; to ensure that this distance is maintained, use smaller plates.
- Don’t put aluminum cookware, like pie plates, cake pans and bread loaf tins, in the microwave. It’s unsafe and your food won’t cook (the metal will reflect the waves rather than letting the food absorb it).
What about microwaving other leftovers? Check out our guide to microwaving takeout containers.
Tips for Putting Aluminum Foil in the Microwave
- There’s some debate about whether the foil’s shiny or dull side should face upwards. The shinier side should be able to reflect more radio waves, right? Not quite. The difference between the reflectivity of both sides is so minimal that it doesn’t really make a difference which side is facing up.
- Check for a microwave-safe label—and for a label that explicitly says it’s not microwave-safe (for example, some microwaveable pizzas include a thin sheet of foil at the bottom, which helps the crust get crispy).
- If your microwave has a metal turntable or metal shelving, don’t use aluminum foil.
- Cover only 1/4 of your food with foil to reduce the risk of fire and to thoroughly heat your food. Because aluminum foil will reflect the radio waves, if you cover all of the food, it won’t heat up.
When it comes to microwaving, it’s always best to play it safe. If you have any doubts, toss your leftovers into a microwave-safe container. In the meantime, we’ll be zapping some of these delicious microwave meals for dinner.