Most types of glass, Styrofoam (trademark), polyethylene, paper, and similar materials do not absorb the microwaves and hence do not heat up. Heating such materials may lead to dangerous situations. For example, aluminum foil heats up very quickly and can start a fire under certain circumstances. Foods cannot be…

Foamed polystyrene is made into insulation, packaging, and food containers such as beverage cups, egg cartons, and disposable plates and trays. Solid polystyrene products include injection-molded eating utensils, audiocassette holders, and cases for packaging compact discs. Many foods are packaged in clear, vacuum-formed polystyrene trays,…

They include styrofoam, used primarily below grade behind frost walls due to its low fire resistance; urethane foam; isocyanurate foam, which has the best fire resistance; and foam glass. Nonrigid insulations are usually made of fiber—glass fiber being the most common—often with a foil-backed paper on one…