Can You Put Aluminum Foil in the Microwave?
Generally, no - aluminum foil should not be put in the microwave. Metal reflects microwaves, which can cause sparks, fires, and damage to your microwave. However, some manufacturers allow small, flat pieces for shielding food if specific guidelines are followed. When in doubt, avoid metal entirely.
Key Takeaways
- Microwaves work by producing electromagnetic waves that are absorbed by water, fats, and sugars in food.
- Foil containers from takeout should never be microwaved unless specifically labeled microwave-safe.
- The inside walls of some microwaves are metal - this is designed differently and does not cause problems.
Explanation
Microwaves work by producing electromagnetic waves that are absorbed by water, fats, and sugars in food. Metal reflects these waves rather than absorbing them, which can cause electrical arcing (sparks) that may damage the microwave or start a fire.
The risk is greatest with crinkled foil, foil with sharp edges, or large pieces. Small, flat pieces of foil used to shield parts of food (like drumstick ends) may be acceptable according to some microwave manufacturers, but always check your specific manual.
A safer alternative is microwave-safe covers, wax paper, or paper towels for covering food. If you need to shield part of a dish, consider rearranging the food or cooking in batches rather than using foil.
Arcing occurs when microwaves induce electrical current in metal that has nowhere to flow smoothly. Sharp edges, points, and thin crinkled areas concentrate this electrical energy until it jumps through the air as a visible spark, reaching temperatures above 1,000°F at the spark point. Flat, smooth pieces of foil without wrinkles are less likely to arc because the current distributes evenly across the surface. The USDA actually states that small, flat pieces of foil can be used to shield thin areas of meat or poultry during defrosting, but the foil must be at least 1 inch from the oven walls.
If sparks do occur, turn off the microwave immediately and keep the door closed until the sparks stop. Open the door carefully and remove the metal. Check the interior walls and the waveguide cover (the small panel on the inside wall) for burn marks or damage. A damaged waveguide cover can lead to further arcing in future uses and should be replaced, typically costing $5-15 for the part. Repeated arcing incidents can damage the magnetron, the component that generates microwaves, leading to a repair that often costs more than replacing the unit.
Things to Know
- Foil containers from takeout should never be microwaved unless specifically labeled microwave-safe.
- The inside walls of some microwaves are metal - this is designed differently and does not cause problems.
- Even microwave-safe metal accessories should be used according to the microwave's instructions.
- Twist ties with thin metal wires are a common accidental cause of microwave sparking; always remove them before heating.