I am planning to make plasma in microwave but the grape method just seemingly sparks and simply isn't impressive. I read some articles and they don't seem to be doing a great job at explaining. So, if someone could explain how to do it with (preferably without) grapes or something else (I believe it can also be recreated with metal) it would be great. Also if you could link me to some actual scientific papers that would be great.

The articles I read: https://www.sciencenewsforstudents.org/article/why-microwaving-grapes-makes-plasma-fireballs https://www.vox.com/xpress/2014/12/3/7326643/grape-plasma-microwave

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    $\begingroup$ With some care, you may consider putting a glass slide of microscopy into a not-too thick walled suction flask, removing most (but not all) air and put this into the microwave oven (Karnes, American Journal of Physics 89, 372 (2021), link (open access) + video). With some pump/thaw cycles, further enriching the remaining air by argon (e.g., from a welder, or protecting gas from the chem lab) you might get closer to the emission occasionally seen for argon (on much smaller scale) in the glove box. $\endgroup$
    – Buttonwood
    Commented Jun 11, 2021 at 19:31

1 Answer 1


Run the following demos with a cup of water in the microwave, and the test object on an inexpensive glass or ceramic plate, to reduce the risk of damage to the microwave itself. Even with care, expect plates to crack, and there is still possibility of damage to the oven. You might also want to remove or cover the light built into the microwave oven to see these more clearly.

  • Incandescent light-bulbs (lamps) are filled with a variety of gases, or vacuum for some. Try a few different clear lamps and watch the glow and spark discharges from the filament. Note the color of the discharge - argon tends towards a purple, nitrogen is more bluish, usw. Use a hand spectroscope and compare the spectra with those of some common gases.
  • Even at atmospheric pressure, helium may glow in a home microwave. Stretch out some steel wool and put it into a flask. Flush the flask with helium from a party-balloon tank to displace air, cap it and put it into the oven.
  • A flame is at least partially ionized. Use one to start the plasma.

Run these test for no more than 15 seconds each, and expect the apparatus to get very hot.


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