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OT: Microwave oven plate.

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  • #16
    Originally posted by Yow Ling View Post
    The glass plate in my microwave is steel, so go figure
    Same here .. Ours is an older late 80's Sharp Carousel with an enamelled steel base plate.


    • #17
      And, only very low resistance metal is a good reflector. Higher resistivity metal will actually absorb some of the power, possibly enough to prevent damage. One suspects that the manufacturer designs the system to work OK with nothing in it, since for sure, someone will operate it like that.

      Raising the material to be cooked is exactly correct.

      The microwaves have a wavelength of around 12 cm or so (2340 mHz). They heat food by the electric field at 2340 mHz vibrating water molecules There is a zero electric field at the metal enclosure, so about 3 cm away there should be a maximum field, on average, assuming standing waves.

      That's just about the height of the middle of a bowl of soup, but items on a plate may be lower. The plate may benefit from raising a bit.

      There is another maximum at 9cm or so, again assuming standing waves. But actual standing waves are unlikely.

      Those are averages, the enclosure and the "stirrer" if present, are designed to give as even a distribution around the enclosure as possible, but they are not perfect, There are always hot spots and areas of little field, so it's not a guarantee.

      The "stirrer" is a rotating device made to radiate the microwave into the enclosure at different orientations, so as to even out the distribution around he interior of the box. So standing waves are prevented as much as possible. But, at around 3 cm off the metal is likely to be the best heating, better than down at the metal surface.
      CNC machines only go through the motions


      • #18
        It also seems that the relative proportion of metal to energy absorbing material in the oven makes a difference. A coffee cup with metallic decoration may crack since the ceramic cup stays cool while the metallic glaze gets extremely hot; but I routinely reheat left over Chinese and Italian take out in their aluminum trays with a piece of wax paper over it. No sparks, no drama, the tray gets as hot as the food inside it. Also, there are plenty of microwave designed fast foods that come in metal rip-top plastic bowls. Tear off the top and microwave. The remaining aluminum ring on the top of the container causes no problem.