Slashdot Mirror

← Back to Stories (view on slashdot.org)

Microwave Experiments Cause Sponge Disasters

Posted by samzenpus on from the can-it-dry-a-wet-cat dept.

gollum123 writes "Reports about a study that found microwave ovens can be used to sterilize kitchen sponges sent people hurrying to test the idea this week — with sometimes disastrous results. A team at the University of Florida found that two minutes in the microwave at full power could kill a range of bacteria, viruses and parasites on kitchen sponges. They described how they soaked the sponges in wastewater and then zapped them. But several experimenters evidently left out the crucial step of wetting the sponge. "Just wanted you to know that your article on microwaving sponges and scrubbers aroused my interest. However, when I put my sponge/scrubber into the microwave, it caught fire, smoked up the house, ruined my microwave, and pissed me off," one correspondent wrote in an e-mail to Reuters."

9 of 517 comments (clear)

  1. A bit silly? by Ckwop · · Score: 4, Informative

    How else did they expect it to work? Of course you need the god-damn water in the sponge. Microwaves have a wave length measured in the centimetre. The size of a bacterial spore is a couple of orders of magnitude smaller The size of a bateria is a lot smaller than this again.

    This means that if you wanted to destroy the blighters with radiation alone you have to choose a frequency a lot higher than microwaves, otherwise there will be areas in the minima of the standing wave that won't heat sufficently to kill the microbes.

    The mechanism for steralisation is through the formation of steam that kills the majority of the nasties - not the microwave energy itself.

    Simon

  2. Stupid People, Stupid Method by StarWreck · · Score: 3, Informative

    The microwave steralizes the wet sponge because it makes the water hot enough to kill anything living. The same effect can be had by dunking the sponge in a pot of boiling water.

    --
    ... and in the DRM, bind them.
  3. No matter what you do... by dtmos · · Score: 3, Informative
    Note that even the original University of Florida press release begins
    PLEASE NOTE: To guard against the risk of fire, people who wish to sterilize their sponges at home must ensure the sponge is completely wet. Two minutes of microwaving is sufficient for most sterilization. Sponges should also have no metallic content. Last, people should be careful when removing the sponge from the microwave as it will be hot.
    *sigh*
    1. Re:No matter what you do... by rsidd · · Score: 4, Informative

      From last paragraph of TFA --that's not the original release, that's the advisory the university issued after all these people burned their sponges.

  4. Sterilising Baby's bottles by REBloomfield · · Score: 4, Informative

    of course, those of us with children and bottle sterlisers know that placing water and objects in a microwave leads to the steam cleaning them... "well duh" was my reaction when i saw this "news" item yesterday....

  5. Re:You're being naive/optimistic by jrumney · · Score: 4, Informative

    People may not understand microwaves, but the original article I saw gave the following advice:

    • Wet the sponge first. Dry sponges will not heat evenly and may catch fire.
    • Keep an eye on the sponge while it is in the microwave and stop the microwave immediately if there is any sparking.
    • 2 minutes should be enough for most bacteria, but never microwave your sponge for longer than 10 minutes.

    Maybe some news sources edited the article down to a short filler piece and left out some of these crucial details.

  6. But do _you_ understand? by KnightTristan · · Score: 4, Informative

    ... how else did _you_ expect it to work?

    A simple question for you: water molecules, are they larger or smaller than the bacteria and spores to be killed?

    Last time I've checked, the wavelength used in the microwave is about 12.5 cm. Sure, the bacteria are much smaller than that, but is it at all relevant?

    KnightTristan

    1. Re:But do _you_ understand? by Dr.+Hok · · Score: 4, Informative

      Last time I've checked, the wavelength used in the microwave is about 12.5 cm. Sure, the bacteria are much smaller than that, but is it at all relevant?

      Actually, the parent does say why it is relevant: there will be areas in the minima of the standing wave that won't heat sufficently to kill the microbes.

      The microwave radiation in the oven is a standing wave. This means there are areas where the radiation is (close to) zero, and the buggers there won't be heated, even if they contain water. Put a sufficiently large chocolate bar into the microwave oven for some seconds and observe the patterns of solid and soft chocolate. Then eat the chocolate, of course.

      The water (steam) is needed to average the heat out over the whole sponge to kill all bacteria in it.

      --
      Say out loud: I'm an Aspie and I'm somewhat proud, I guess. Uh. Can I write an email in all caps instead? Hm...
  7. Re:Incoming lawsuits in: by ArsenneLupin · · Score: 3, Informative

    Since a microwave does a great job of restoring a piece of dried bread to something edible (by heating and expanding what little water is present in it), Careful here. Dried bread does catch fire when left in the nuker for too long. And sometimes that too long is not long enough to make it soft (I made that experience years ago with a dry piece of French baguette... maybe different kinds of bread behave differently...)