What types of plastics are microwavable?

There are no "microwave safe symbols" in common use. Obviously, plastics vary in their chemical composition. What they have in common is that they are formed by chemical reaction. If used with food in a microwave, • they must not further react; • they must not decompose into the food; and • they must not leach out components into the food. The important thing is to identify those plastics which are microwave-safe. There probably are plastics which are safe for microwave use. The epoxy material used in microwave construction is an example of this (although generally not in contact with the food). NSF, which certifies food-safe items, states: • Only use cookware that is specially manufactured for use in the microwave oven. Glass, ceramic containers, and all plastics should be labeled for microwave oven use. • Never use plastic storage containers such as margarine tubs, take-out containers, whipped topping bowls, and other one-time use containers for cooking or reheating food in your ...  more