What Kind of Metal Goes in a Microwave?

Aluminum Foil

• Small pieces of foil are safe for covering limited parts of food in the microwave to prevent their overcooking, according to the U.S. Department of Agriculture. Use only smooth foil to prevent sparking, and leave at least three-quarters of the food uncovered. Keep the foil at least 1 inch away from the walls of the oven. Do not allow foil to come near any other metal in the microwave, such as metal shelves. In sparking occurs, remove the foil at once. The USDA recommends always following your manufacturer's instructions regarding using aluminum foil in microwaves.

Other Metal Items

• Some ready-prepared foods come in microwavable packages containing aluminum foil. Consult the package directions to find out whether microwaving is permissible. If so, follow the directions for safe microwave heating. Do not allow microwavable foil containers to come in contact with other metals in the microwave, such as shelves. Cookware clearly labeled for microwave use is safe in the microwave. In addition, containers and racks made specifically for your model are safe to use. You can only use meat thermometers that are especially designed and labeled for microwave use. In any case, follow your oven manufacturer's instructions.

Dangerous Items

• Ordinary metal cooking and baking pans are not safe for use in the microwave. Similarly, metal twist ties or food wrapped on all sides with aluminum foil are unsafe in the microwave, according the USDA. Non-approved thermometers, foil liners, staples or dishes with silver, gold or other metallic glazes are unsafe. Serving dishes or other items made of pewter, gold or silver are unsafe.

Testing Items

• The USDA provides a method for testing whether items are safe in the microwave. Put 1 cup of water in a microwave-safe glass container. Put the item you wish to test and the cup of water in the microwave. Do not let the cup of water touch the unknown item. Run the oven at full power for one minute. Open the oven, and touch the unknown item. If it has become hot or warm, it contains metal and is unsafe for the microwave. Using an unsafe container can damage the item or the microwave oven.

Warning

• Items that contain metal can cause arcing or sparking inside the microwave. Often the cause is metal rims on dishes or small pieces of metal, such as twist ties. However, some foods, such as hot dogs and carrots, can also cause arcing if they contain concentrations of certain additives or minerals. If you see sparks, the FDA recommends turning off the oven at once because arcing can damage the oven. However, immediate action should prevent damage. Change the food to a different container, or cook it in another way.