Microwave Safe Containers and Covers
Containers for microwave main dishes should be made of materials that allow microwave energy to pass through. Your best choices are heatproof glassware and ceramics, and heatproof plastic (thermoplastic) designed for microwave cooking. Besides bowls, baking dishes, and casseroles, you’ll find glass measuring cups in a range of sizes very useful; they’re particularly handy for making sauces and gravies.
CAUTION: Avoid metal containers and any dishes with metallic, especially gold or silver, trim (gold-rimmed china plates, for example). Metal reflects microwaves and may cause arcing in the oven (you’ll see what looks like lightning or sparks). Arcing can eventually damage the magnetron tube.
Pottery, plastic, and china may or may not be appropriate for the microwave. In some cases, these materials have components that interfere with the transmission of microwaves, so check with the manufacturer to make sure your dishes are microwave-safe. If you’re not certain, you can find out by performing this test. Fill a glass measure with 1 cup water, then place it in the microwave alongside the dish in question. Microwave on HIGH (100%) for 1 minute. Only the water should get hot; if the dish heats up too, don’t use it in your oven.
Plastic foam plates and cups are suitable for heating food just until warm, but don’t use them for actual cooking.
Plastic bags can be used in the microwave if they’re the heavy-duty type; avoid the thin plastic bags provided in the produce departments of most grocery stores. To close the bags, simply knot them at the top; or use a piece of string, a plastic holder, or a rubber band. Don’t use twist ties, since they contain metal.
Paper plates, cups, napkins, and towels can be used in the microwave.
Plastic wrap and glass or ceramic lids are good container covers. These are the best choices when the recipe tells you to “cover and microwave.” We recommend using the heavy-duty plastic wrap specifically designed for microwave use; lightweight, inexpensive wraps may split during cooking and melt into the food. (Don’t use plastic wrap to cover a hot microwave browning dish, though; always use the dish lid.)
Wax paper is appropriate when you want to cover foods loosely.
Aluminum foil is a subject of some controversy among microwave manufacturers. Most makers agree that a limited amount may be used to shield parts of food that are likely to cook too fast—wing tips of poultry or tails of whole fish, for example—but others oppose using foil at any time. Check your owner’s manual to see what’s recommended for your particular oven. We do not recommend using foil in our recipes.
