Why do microwave ovens heat food but seldom heat the dish the food is on?

Answer 1

Microwave ovens heat by passing specific frequency micro-waves though food. Only certain molecules, fat and water, are affected by this, as there is no water or fat in a plate so this will only get warmed though contact with the heated food...

Answer 2

Plates do not contain moisture or metals. Those are the things heated by microwaves. Some plates and glassware DO contain metals, and are not safe for use in a microwave. it heats the plate up if u use china

The answer above is only partially correct. The reason the food heats more is because it is more receptive to the microwave energy and able to convert the microwave's energy to food heat - that's usually due to the water & some other food ingredients. Plates usually are not receptive and won't eat, especially when there is food present (it uses most of the energy). However, not all plates stay cool. Plastic dishes, other than melamine (Melmac - never microwave) usually stay cool: same with glass. If the glass seems hot it is due to the transfer of heat from the food. But china dishes may get hot. There are two types of china: glazed and non-glazed. The non-glazed dishes can get hot if they absorb water when being washed. Glazed china can get extremely hot if the glaze is not properly formulated. Many of the dishes made in China today can get dangerously hot - 300 F.

Answer 3

Microwaves work with moisture, the more watery something is, the hotter it gets. Plates have almost no water in them, so they don't heat up, but the heated food transfers it's heat to the dish. Hotpads recommended!

Many foods have a great deal of water in them and that's why they heat well within microwave ovens, although water is not the only thing that will heat in a microwave oven. Dishes generally don't heat because they are made of materials, such as ceramics, that are relatively microwave transparent (that means that they can't capture the microwave energy that creates the heat). However, that's not always the case. For example, unglazed ceramic dishes may absorb water, either from the food, the dishwasher, immersion in water, etc. In that case, the dish will get hot because the water inside the dish has gotten hot. On the other hand, glazed ceramic dishes should not get hot. But again, that's not always true, because some glazes are improperly formulated and actually can get very hot. In one laboratory, some glazed dinnerware that have been manufactured in China and was supposed to be "microwave-safe", was found to reach temperatures as high as 300°F. So the warning to always use a hot pad should be followed.