1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Rust from my microwave ruined a nice bowl of soup and also my day

  1. Feb 12, 2012 #1
    Hello all,

    Upon enjoying a nice hearty bowl of tomato soup, warmed conveniently in my microwave, I noticed a few mysterious specks of something dark floating around. On inspection it turned out that this was rust that had fallen from the roof of my microwave.

    Being a rather anxious person, my first thought was that I had ingested some terrible radioactive pieces of metal and that I only had minutes to live. However some internet research somewhat alleviated these fears, mainly due to the fact that microwaves are non-ionising. However the risks of eating rust from a microwave were not conclusively answered.

    I know that eating a bit of rust will do nobody any harm, however I wanted to ask your expert advice as to whether rust from a microwave was somehow more harmful? My logic behind this, almost certainly flawed, is that after years of being beamed with microwaves, could the rust somehow have become toxic?

    Thanks in advance for your replies, I know this may be a silly question, but sometimes my anxiety just won't go away until I receive a factual answer.
  2. jcsd
  3. Feb 12, 2012 #2


    User Avatar
    Science Advisor

    Rust is rust. Certainly, there is nothing "radioactive" about a microwave oven. And microwaves cook food primarily by boiling water in the food. They are not going to do anything to the metal in the oven itself except heat it.
  4. Feb 12, 2012 #3
    Also, microwaves don't actually have microwave fields (why we haven't fixed their name, I don't know). Microwaves are more like hundred-mm-waves. In the whole EM spectrum, that's weak sauce. DNA damage will happen at energies of about 1eV, and microwaves have 1e-5eV.

    The only thing microwaves do is jiggle dipoles -- the dipoles in food are mostly water. From thermodynamics we know that the faster a molecule moves, the "hotter" a system is. Jiggling dipoles equal speed.

    Rust is iron oxide. We require iron for our blood. No harm in eating it. I do not, however, know if there is a harm in saturating your body with iron. So, I guess, be safe and don't gobble up all the rust. ;)

    I didn't even realize that microwaves could get rust, must be pretty old and pretty uncared for.
  5. Feb 12, 2012 #4
    Keep in mind that all those "iron-enriched" cereals actually have iron iron powder on them. If you grind them and pass a magnet, it will collect pure iron powder.

    Not sure what kind of iron they put in these cereals, though. I suspect it will have some oxides in it, but no proof about that.
  6. Feb 12, 2012 #5
    You can prevent that by covering your food with a paper plate. That will keep the top from rusting out.
  7. Feb 14, 2012 #6
    If the microwave is getting that decrepit maybe you should get a new one? If you are getting sharp edges and holes inside the microwave you might get arcing, and or excessive microwave leakage. It can interfere with cordless phones.

    Also, the metal inside my microwave is painted or coated with a white material, paint or plastic?

    You've probably eaten some of that too. I suppose it isn't toxic, but another reason to get a new one.

    BTW, are you sure it's rust?? Might be baked on spaghetti sauce from that boil over last week you didn't clean up very well . .

    ; )
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook