Catch up on stories from the past week (and beyond) at the Slashdot story archive


Forgot your password?

Science in the Microwave 95

Sunda666 writes "I have just hit this site which describes in detail how to build an one-atmosphere plasmoid using ordinary stuff and a microwave oven. Interesting thing, i'll try it as soon as I get a spherical glass vessel like that ;-)"
This discussion has been archived. No new comments can be posted.

Science in the Microwave

Comments Filter:
  • by a3d0a3m ( 306585 ) on Saturday March 16, 2002 @06:12AM (#3172583) Homepage
    This has been done before, and posted to slashdot before. You can do it without the glass vessel. There's an old quickies here [] that shows how to do it without the vessel.

  • Sci-Home (Score:2, Interesting)

    by linuxator ( 529956 )
    Rules :)
    How many CD's have you burned in your microwave oven? And have you build your own Tesla trafo? If not, then give them a try also...
  • by Greyfox ( 87712 ) on Saturday March 16, 2002 @06:13AM (#3172588) Homepage Journal
    This is extremely hazardous and should never be tried at home. That's what the microwaves at work are there for!
  • The page has a bunch of warnings saying that you shouldn't keep the microwave on for more than 10 seconds because the glass container is getting hot... If you do and it melts the glass, will it attack the ceiling of the microwave itself next? =)

    Anyone have a spare microwave they don't mind sacrificing to see what happens if you just keep it going? :) (don't forget to document and give us a link!)
  • I watched the video after reading the article, and I must say I'd be getting the hell out of there when it flashed that bright blue... Seriously, it's quite an interesting experiment, though I'd be afraid to put anything other than food in my own microwave.

    Their article on their GDP thruster design is also pretty interesting - does anybody know how viable this would actually be?
    • Re:GDP thruster? (Score:2, Informative)

      by Anonymous Coward
      ...though I'd be afraid to put anything other than food in my own microwave.

      Who said you had to use your own? 7-11's, university canteen's, your workplace, etc. all have "public access" microwave ovens which are perfect for this purpose...

      Other items of interest:

      • eggs (you said you were only concerned about putting non-food items inside...)
      • pencils: they'll burn pretty quickly
      • pencil mines: they get so hot that they can melt glass...
      • soap: if you try this, make sure your microwave oven is very big (or only use a rather small filing of soap
      • the newest MSDN CD's from work (perfect for doing in the office kitchen!). Those make great office ornaments, but it's probably best if your boss and/or colleagues don't see them... Microsofties are known for their lack of sense of humor, and might not appreciate it...
      • chocolate, bread (again, if you're concerned about putting non-food items inside...)
    • Re:GDP thruster? (Score:2, Informative)

      by Sunda666 ( 146299 )
      GDP thrusters are a very kewl concept, but I think they might be very poluent.

      Man, that site is full of cool research, check it out, especially the lifter experiments.
  • Just as much fun... (Score:4, Interesting)

    by Deltan ( 217782 ) on Saturday March 16, 2002 @06:17AM (#3172596)
    Take a non conductive container and fill it part way with water. Take your standard every day 60 Watt light bulb and submerge the threaded end into the water. Put the container into the microwave & turn it on.

    Fun light show...wheee!
    • Quite true! It's interesting that the resulting light show is _not_ monochomatic, as you might expect -- it flashes through many colors. Definitely worth doing.

      I'm not sure whether it matters that the threaded end is submerged (or even touching the water), though. I've always had it that way, but only because that's how the bulb sits. Maybe I'll have to try...

      • by Deltan ( 217782 )
        If the threaded metallic end is not submerged the metal will spark in the microwave and you might blow up the whole works.
        • I've sparked metal in the microwave before (aluminum foil or an old CD). What's the danger? What exactly is going to "explode"?

          True, you don't want to do it heavily or with an otherwise empty microwave; the magnetron has enough heating problems anyhow (hear that noisy fan?); but that's why you also use a dish of water, to give the microwaves something to be absorbed by. Note that the water isn't conductive (we're not adding salt), so there's no reason for it to innately prevent sparks.

          I'm going to have to try this with my spare microwave. While hiding behind a concrete wall, holding a panic switch. I'm a pyro, not an idiot :-).

          • Well.. the first time I tried it the tip wasn't submerged the whole way and the bulb exploded in the microwave. I'm not sure if that was the reason it happened but after fully submerging the threads it just gave me a pretty light show.
            • Facinating! I'll have to try to recreate that. Was there any microwave damage?

              I know that I've done it before without complete submersion -- perhaps I was just (un)lucky, or perhaps only the tip matters, or maybe it only hurts if there's sharpened metal (that's a general rule with MWs -- area doesn't matter, only edge).

              Thanks for the pointers -- and I think I'll have to say that newbies should start by submerging their threads. At least until we figure out why yours exploded.

              Anyhow, this is probably my favorite demonstration; quick, easy, cheap.

  • by j3110 ( 193209 ) < minus math_god> on Saturday March 16, 2002 @06:19AM (#3172598) Homepage
    I was going to try this a year ago, but decided that I didn't really need a darwin award :) You can do it with any glass bowl and anything that burns in any microwave that you feel safe doing it in :) The brown gas you see, NO2, is toxic and is found in cigarette smoke. Be careful, it's arguably the most harmful substance in cigarettes. Not good for the atmosphere either :) I really don't think there is that much in cigarettes, and I would urge anyone foolish enough to do this (like me after a few drinks) to NOT breath the funky air! :)

    You have been warned! :)
    bad stuff really :) when it dissolves in your lungs, it's likely to make nitric acid, which is like to make your lungs liquid if you breath too much.
  • The cavity magnetron was a state secret [] during the Second World War.
    Now it's the centerpiece of an, oh, maybe $80 toy [], destroyed in the name of junk science.
  • by eram ( 245251 ) on Saturday March 16, 2002 @06:35AM (#3172621)
    Some other potentially dangerous experiments with CD:s, light bulbs and other objects in microwave owens can be found here []. Looks interesting, but I personally wouldn't do that in my own kitchen.
    • I just tried the lightbulb. It was quite impressive: no results for about two seconds, then some very pretty colors, though I was slightly worried that somehow the radiation produced would be unhealthy. I hope not. After a few seconds (10 or so), it exploded, with little bits of glass coating the bottom of the microwave.


      Good thing I was already planning on doing some cleaning today.

  • by Anonymous Coward
    There's tons of interesting research on that site,
    like field effect propulsion and antigravity.
  • I read the article. It looked kinda nifty, but I wanted to know more, since I was still very fuzzy on exactly what the heck a plasmoid was. I searched on google, and that page was the #1 result, and it was #5 on Ask Jeeves.

    I kinda like asking Geeves questions "Hey Jeeves, old buddy, do you happen to know what the heck a plasmoid is?" It's so much more conversational than barking orders like "plasmoid" at google. *grin*
  • by Oink.NET ( 551861 ) on Saturday March 16, 2002 @07:09AM (#3172654) Homepage
    For an even quicker thrill, try putting marshmallows in the microwave.

    For those too lazy to actually get up, find marshmallows and find microwave, use this applet [] to cook them virtually, or check out this time lapse video [].

    For those craving more of an intellectual thrill, find the speed of light with marshmallows [] using a microwave.

  • i may have missed something in the article, but when does a substance qualifies to be a 'plasma'?
    It sure looks nifty but that can't be a criterium, right?
    • An electrically neutral, highly ionized gas composed of ions, electrons, and neutral particles. It is a phase of matter distinct from solids, liquids, and normal gases.
    • Often gas that is emitting light is being falsely named plasma, but the atoms are only being stimulated by heat or light and emit light. A real plasma is a gas which is stimulated so high that the atoms are ionized and free electrons are floating between them.
  • by MyNameIsFred ( 543994 ) on Saturday March 16, 2002 @08:20AM (#3172724)
    30 years ago my father owned an applicance store, back when microwave ovens were becoming popular. GE told the store owners about some neat tricks to impress the customers.

    Nothing draws them in like putting light bulbs in the microwave and letting the magic turn them on.

    Not too long after they told us how to do the tricks, GE yelled STOP. It's scaring the bejebbus out of the public. We're getting frantic calls about the death rays.

    How times have changed.

  • Easier way (Score:2, Interesting)

    by vossman77 ( 300689 )
    We used to build plasmoid balls as physics demos for kids. My professor said it isn't bad on the microwave either.

    Instead of building that complex machinery list at the webpage all you need is a standard 2-liter bottle of soda (pop for Midwesterners, coke for Texans). Cut the bottom off and discard the top (usually about 3-4 inches should do) poke hole in the side for airflow.

    Now you need something to hold the match upright e.g. a.b.c. gum or a cock like them.

    Light the match close the door, start the microwave. Eventually your 2-liter will melt causing even more fun.

    • by JonWan ( 456212 )
      Now you need something to hold the match upright e.g. a.b.c. gum or a cock like them.

      I think I'll pass on that one.;-)

      Tune in next week when we will show you how to build a hydrogen fusion containment vessel using your bath tub.
  • You wanna make plasma? Light a match.
    • Re:Big deal (Score:3, Informative)

      by XNormal ( 8617 )
      The flame of a match is just hot gas, not plasma. The flame's light comes from incandescent particles of carbon, not ionized atoms.
      • Hot flames most certainly are ionized which is why this experiment doesn't work well with candles because the flame is too cool. The ionized carbon from the toothpick burning is what is causing the light in this shmoo. Another experiment is to ionize water and spray it out of a mister, if you light a match or other moderately hot flame and put a paper card between the mist nozzle and flame the water will go under the card and extinguish the flame. There's a sprinkler system designed for data centers which instead of normal sprinklers uses ionized misting nozzles to spray a sort of ionized fog which is attracted to the flame and snuffs it out.
  • The first description on the website below on generating ball lightning using a Tesla coil seems to use the same concept for an ignitor and relies on carbon soot for ball formation. .html
    Whats the link's here people? A fair bit sounds the same. Now if you could get ball lightning inside your microwave, the sort that goes through glass....
  • by Alsee ( 515537 ) on Saturday March 16, 2002 @10:19AM (#3172902) Homepage
    If you look deeper into the website you'll see that the author goes into detail analyzing the sound produced. The humming sound is simply the frequency of the microwave electronics. The plasma itself would normally be silent. It is acting as a "speaker" based on the varying energy it gets from the microwave oven. If you take a look here [] you'll see projects that use the plasma effect as an extremely high quality tweeter.

    • The 250Hz sound is the 5th harmonic of the mains power (electricity in France is 50Hz). If you look carefully at the spectrum you will also see a small peak at the 3rd harmonic (150Hz). The glass vessel and/or the microwave oven itself act as a resonant cavity that emphasizes these frequencies. The fundamental frequency (50Hz) is so weak that it drowns in the noise. There are no even harmonics because the waveform is symmetrical.
  • Just tried it out... (Score:4, Informative)

    by BlueUnderwear ( 73957 ) on Saturday March 16, 2002 @10:20AM (#3172906)
    Having no suitable sperical vessel ready, I used a sawed-off plastic mineral water bottle. Having no tooth-picks ready either, I just stuck the match itself into the cork. As recommended in a previous Slashdot story about the subject, I removed the revolving plate, and put a glass of water into the back.

    First attempt: the match always went out before it could produce any plasma ball. D'oh

    Second attempt: rather than using a match, I stuck a long pencil mine into the cork, and set the oven to thirty seconds. 29 seconds of nothing. Then a loud whizz, and the time ran out before it could get any more interesting (should've set it to a minute). However, this one second of action was enough to fill the bottle with a mysterious thick white fume. Question: is this the nytrogen oxyde that the article speaks about, or was it only the plastic burning (other than the fumes, there were no obvious traces of burn on the bottle). Worrying that the fumes might be toxic, I didn't repeat the experiment.

    • Ok, curiosity was stronger than worry:

      Third attempt: more or less same setup as previously, but a little less water in the "load" glass, and using a larger cork, so that the mine could stand upright without leaning against the bottle. A spark appeared already early on in the experiment, but didn't cause a ball. However, the same candle-flavored fumes started appearing again. Then it hit me: they came from the cork, which was heated by the pencil mine stuck into it. Indeed, the cork had small traces of burn. Still no plasmoid, alas.

      Fourth attempt: Figuring that strength of microwaves might depend on orientation, I broke a small piece off the mine, and stuck it into the cork, horizontally, rather than vertically. Soon indeed sparks, and then a ball of fire appeared, but unfortunately the pleasure was rather short-lived: the plasmoid set fire to the plastic bottle, and thus I had to stop the mess. Ok, I'll have to hunt for a suitable glass vessel.

      • Ok, I'll have to hunt for a suitable glass vessel.

        Go to Home Depot or any home improvement store and go to the lighting department. You can get glass globes for light fixtures for a couple of bucks. I can only assume they are heat tolerant, as lightbulbs get prety hot.

  • big fun time (Score:2, Interesting)

    by 68030 ( 215387 )
    I've tried this several times with varying
    degrees of sucsess. For those of you with
    plenty of time, try repeating the experiment
    with a glass container not given enough
    ventilation. When the plasmoid ignites
    (lights? is born? stabilizes?) it radiates
    a lot of heat. Without proper ventilation
    the glass vessle will jump upwards with a
    satisfying bang. The flash is quite impressive
    for the easily amused.

    As for the sound, there is some sound produced
    other than the low pitch hum of the microwave
    itself, sort of a buzzing noise.

    I once saw a page describing this experiment,
    but this person had taken the magnetron tube
    out of the microwave, mounted it in a very
    sexy looking raygun type configuration. It
    looked exceedingly dangerous. I'm sure all the
    reflected radiation was an excellent
    stimulation to his fertility.

    Such wonderful toys.
    • To quote my conversation with my roommate who wished to reproduce the results of his experiment one of the first time this showed up on Slashdot.

      Me: So what are you going to do after you are done, i.e. made the Plasmoid Fireball?

      The Roommate: We'll just open the door and let it go free like nature intended.

    • I made a microwave gun in electronics. Proper shielding, power, everything. I was..16 maybe? I made sure it was safe on me. My first experiment was to aim it at a computer. Insta-bluescreen/reboot. That was cool. I also told the people around me not to step in front of it, but apparently they had more things to worry about than the thermal integrity of their flesh/organs/pocket contents.
  • While I think the concept of this method is sound, the classic method works well too. Take enough "steel wool" (the real stainless stuff works best) and spread out to about 25^2cm. Finely grind some charcoal and place a couple grammes on the cleaning pad. Place this whole thing on a ceramic surface that can take *extreme* tempatures. Turn the nuker on high (600W is wimpy -- use a dual-magnetron 2000W model for best results) and watch the show. Beware it gets very hot, so when the plasma really gets going, its time to quit.

    It is fairly safe, but the oven should be 'expendable'. AFAIK, no toxic fumes are produced as in the case of CD's and if you don't destroy your oven, you can still warm over your food.
  • Hey Johnny, want a neat project for science fair? Here's how you trash mom's microwave, make toxic gases, and endanger your reproductive future all in one simple experiment.

    This same page was posted a year or so ago. It's neat, it's fun, it has geek-appeal, and it's mildly dangerous in an MTV "Jackass" sort of way. :)
  • The greater context [] of this guy's site is a series of experiments aimed at using plasma generators to provide thrust for a new generation of aircraft. With one type of thruster, they've achieved accelerations up to 480 m/s (for the liquid medium, not the aircraft, not yet.)

    This was news to me, and I'm finding the concept and science [] behind plasma thrusters fascinating (this is a link off the microwave page.)

    Plus, there's a far more interesting experiment, where he shows you how to build your own plasma panel [].
  • I've done this. Take lit matches and put them in the microwave. They will make blue or white bursts of plasma. It's great fun!! Also try steel wool.It makes all sorts of sparks. If you take a paperclip and bend it so the two ends are about 3 cm away from each other, you can make a great arc that can melt stuff.

    The plasma thing with the match works because the flame is plasma. Plasma absorbs microwaves. The microwave energy heats the flame more, superheating air around it, and it makes a big burst of brillianltly bright plasma, sometimes. Ive had huge bursts that go up to the top of the microwave out of a little burning match.

    It is completly safe to you. Absolutely safe. Once the microwave is off the plasma/arc/whatever instantly dissapears since it's power source is cut off. It may not be safe for your microwave.

    To be safe with you microwave, take these steps:

    1. Have a cup of water off in the corner of you microwave.
    This prevents your magnetron from overheating by absorbing excess microwaves. Yes, it may reduce the intensity of the plasma a little, but it saves your microwave. If you do this, there is no real way of hurting your microwave. The magnetron can't be fried if you got some water in there. The worst that could happen is you could get scorch marks in your microwave.

    2. Limit the time to about 20 secs. The cup of water should prevent anything bad from happening. Just to be safe though.

    Also, use matches, not a candle. A candles' flame is not hot enough to absorb enough microwaves to make a good plasma.
  • Go to you local home improvement store - in the lighting section you can buy clear glass covers for external post lamps. Be care when using them to experiment with microwave plasmoids - the glass is cheap and will easily crack under the intense heat of a plasmoid.

    also, beware that plasmoids produce 'real' heat that will keep the glass hot for a longer period of time (as opposed to the 'fake' microwave heat that seems to quickly dissipate)


In seeking the unattainable, simplicity only gets in the way. -- Epigrams in Programming, ACM SIGPLAN Sept. 1982