• Question: why can't you put metal in a microwave, but it is made out of metal????

    Asked by missjmrt to SJ, Paige, Gem, Andrew on 25 Jun 2012.
    • Photo: Andrew Thomas

      Andrew Thomas answered on 25 Jun 2012:

      This is a bit of a myth. You can put metal in a microwave but it can be dangerous. The metal must be very smooth and have no sharp bits, so a spoon might be OK but a fork or knife wouldn’t. Also very thin pieces of metal can be dangerous because the microwaves induce currents which can cause heating. Most microwave manuals will tell you that if your food is cooking faster in some places than others you can use aluminium foil to wrap those bits because they block the microwaves. Kitchen foil is thick enough to use.

    • Photo: SarahJayne Boulton

      SarahJayne Boulton answered on 26 Jun 2012:

      Did you know microwave are a kind of radio wave? when you make radiowaves with a frequency of about 2500 megahertz (that’s 2500 000 000 waves a second!!) they can be absorbed by water molecules, generating heat! That’s how stuff cooks in a microwave!

      Metal however reflects microwaves, like Andrew said, this would stop the food from cooking as quickly as other parts. The metal shielding inside a microwave acts to keep in as many microwaves as possible, however if you take a look insdie one, you’ll see theres generally a little cardboard of plastic hole that acts as a safety mechanism.

      Two bits of metal close together in a microwave will start to spark as the energy of the microwaves excites electrons in the metal, this is when things start to get dangerous.

      I’m with Andrew on the danger part 100% – however – there are people in the world that have taken all the safety precautions possible to show you exactly why it is so dangerous.

      Maybe you might want to see what happened on the show Brainiac when ‘things’ (CD’s, Fairy lights, Champagne…) got put in microwaves…

    • Photo: Paige Brown

      Paige Brown answered on 29 Jun 2012:

      I think actually that the inside of a microwave is NOT metal, but rather a material like glass or hard plastic that coats the inside. Have you noticed that the turning wheel in your microwave has no metal parts? The outside of the microwave may perhaps be metal, but that is ok because the microwaves are stopped by the inside coating of your microwave!

      Now, why can’t you put metal IN the microwave? It’s because metal doesn’t have water! You don’t really want to put ANYTHING in the microwave that doesn’t have some amount of WATER or FLUID in it:

      “Microwaves happen to not pass right through water. Nor are they completely reflected by water. So, when we put something with water in it in the path of microwaves, say a potato or popcorn kernel, the water molecules start tumbling and jostling like crazy. The energy of the rubbing water molecules turns to heat. Your potato or popcorn heats up. When these waves hit metal like the aluminum foil or gold paint, the metal absorbs the microwaves like an antenna. The energy doesn’t turn to heat, roughly because metal is not water. (You know that, too.) The microwave energy has to find a place to go. It usually forms sparks that jump from air molecule to air molecule all the way back to the metal sides or bottom of the oven. Where the sparks comes and goes from the aluminum foil or metal paint, it gets hot. The energy is concentrated. It often burns a tiny hole or pit in the metal. It’s energy just looking for a place to spread out. It can’t; so, don’t put metal in a microwave.”

      http://www.ccmr.cornell.edu/education/ask/index.html?quid=582

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