# Is it dangerous to turn on an empty microwave? **URL:** \ **Category:** Factual Questions\ **Created:** [January 7, 2004, 7:32am UTC](https://boards.straightdope.com/t/is-it-dangerous-to-turn-on-an-empty-microwave/223175 "2004-01-07T07:32:43Z")\ **Posts on this page:** 16\ **Page:** 2
**Author:** ![SlackerInc](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/slackerinc/32/275_2.png) [@SlackerInc](https://boards.straightdope.com/u/SlackerInc)\ **Post date:** [October 2, 2013, 9:37am UTC](https://boards.straightdope.com/t/is-it-dangerous-to-turn-on-an-empty-microwave/223175/21 "2013-10-02T09:37:04Z")
There was no metal in it, and it had always run fine until this happened (and was less than a year old, and our “auxiliary” microwave, only used about three or four times a week). It was however a small microwave that was the absolute cheapest model available at Wal-Mart, so there’s that. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [October 2, 2013, 9:16pm UTC](https://boards.straightdope.com/t/is-it-dangerous-to-turn-on-an-empty-microwave/223175/22 "2013-10-02T21:16:42Z")
> [@Achernar](#): > > My microwave does not warn that it should not be turned on when empty. Why not? Because if you do ruin it by running it empty, you will buy a new one – more profits for the manufacturer! ---
**Author:** ![TBG](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@TBG](https://boards.straightdope.com/u/TBG)\ **Post date:** [October 2, 2013, 10:59pm UTC](https://boards.straightdope.com/t/is-it-dangerous-to-turn-on-an-empty-microwave/223175/23 "2013-10-02T22:59:05Z")
> [@t-bonham@scc.net](#): > > Because if you do ruin it by running it empty, you will buy a new one – more profits for the manufacturer! Not if you do that while it’s still under warranty! Anyway, just got a new microwave earlier this year, and it definitely had the warning in the manual. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [October 2, 2013, 11:33pm UTC](https://boards.straightdope.com/t/is-it-dangerous-to-turn-on-an-empty-microwave/223175/24 "2013-10-02T23:33:54Z")
> [@TBG](#): > > Not if you do that while it’s still under warranty! No, that would be misuse of the product, and would not be covered by the warranty. ---
**Author:** ![picunurse](https://avatars.discourse-cdn.com/v4/letter/p/7bcc69/32.png) [@picunurse](https://boards.straightdope.com/u/picunurse)\ **Post date:** [October 3, 2013, 12:25am UTC](https://boards.straightdope.com/t/is-it-dangerous-to-turn-on-an-empty-microwave/223175/25 "2013-10-03T00:25:41Z")
Check the mica cover that isolates the magnatron. If it has a black spot or a hole in it, it needs to be replaced. Don’t go to a small appliance repair shop, go to Lowes or Home Depot and get a sheet of mica, then, using the old one as a template, cut a new one and replace it. The small appliance repair shop will charge upwards of $40, whereas a 10"X10" sheet of mica will be less than $10. ---
**Author:** ![SlackerInc](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/slackerinc/32/275_2.png) [@SlackerInc](https://boards.straightdope.com/u/SlackerInc)\ **Post date:** [October 3, 2013, 9:45pm UTC](https://boards.straightdope.com/t/is-it-dangerous-to-turn-on-an-empty-microwave/223175/26 "2013-10-03T21:45:04Z")
Too late, threw the microwave out already. ---
**Author:** ![EmptyMicrowave](https://avatars.discourse-cdn.com/v4/letter/e/a9a28c/32.png) [@EmptyMicrowave](https://boards.straightdope.com/u/EmptyMicrowave)\ **Post date:** [October 5, 2015, 7:55pm UTC](https://boards.straightdope.com/t/is-it-dangerous-to-turn-on-an-empty-microwave/223175/27 "2015-10-05T19:55:34Z")
Hey, made this account (as you can tell by the name lol) just to respond to this, for some reason. I left my microwave on empty for about 1 minute a couple years back. It was an old crappy microwave, not sure which brand or model/make or year etc. Anyway, it was set to run for about 3 minutes, but about 1 minute in I heard weird static noises and saw light flashes from around the corner. I go in and it’s straight out of a sci-fi movie lol long blue electricity bolts flying out of it all over the place. I was freaked out to get close, but I just kind of bolted in and hit Stop. This is 100% true btw no exaggeration. I have a question though, I’ve been wondering about it since it happened - Would I have been electrocuted slightly, or inflicted with slight radiation or just lightly shocked if I had made physical contact with these crazy electricity bolts? Thanks! ---
**Author:** ![Thudlow\_Boink](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thudlow_boink/32/320_2.png) [@Thudlow\_Boink](https://boards.straightdope.com/u/Thudlow_Boink)\ **Post date:** [October 5, 2015, 8:01pm UTC](https://boards.straightdope.com/t/is-it-dangerous-to-turn-on-an-empty-microwave/223175/28 "2015-10-05T20:01:06Z")
Has Mythbusters ever done anything with microwave ovens? ---
**Author:** ![SlackerInc](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/slackerinc/32/275_2.png) [@SlackerInc](https://boards.straightdope.com/u/SlackerInc)\ **Post date:** [October 5, 2015, 8:06pm UTC](https://boards.straightdope.com/t/is-it-dangerous-to-turn-on-an-empty-microwave/223175/29 "2015-10-05T20:06:32Z")
I have only watched about ten episodes of the show, but I remember them doing one on the myth that microwaves cook from the inside out. They put a big hunk of meat in one and found that the outside was more cooked than the inside. (Still, I think calling this a “myth” is extreme, as it is clearly less “outside-in” than a conventional oven.) ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [October 5, 2015, 8:51pm UTC](https://boards.straightdope.com/t/is-it-dangerous-to-turn-on-an-empty-microwave/223175/30 "2015-10-05T20:51:39Z")
BRRRAAAAIIIIINNNNSSSSS!!! (It’s the second time this zombie thread has been raised) > [@EmptyMicrowave](#): > > I have a question though, I’ve been wondering about it since it happened - Would I have been electrocuted slightly, or inflicted with slight radiation or just lightly shocked if I had made physical contact with these crazy electricity bolts? There’s no “radiation” in a microwave, at least not in the way that the term is commonly used. Microwaves use radio waves to cook your food. So you don’t have to worry about any kind of radiation risk. The way most people use the term “radiation”, they are referring to ionizing radiation, and microwave radio waves are too low in frequency to be ionizing. The spectrum goes long waves, radio waves, microwaves, infra-red light, visible light, ultra-violet light, x-rays, gamma rays, and cosmic rays. Part way through the ultraviolet part of that is where it starts to get ionizing, which means that the electromagnetic radiation will strip the electrons off of atoms and create ions. This causes cell damage, cancers, makes your hair fall out and you die, that sort of thing. So, high enough frequency ultraviolet, x-rays, gamma rays, cosmic rays, all ionizing. Visible light, infra-red, microwaves, radio waves, long waves, all non-ionizing, so no Godzilla-creating type of radiation here. Your sci-fi light show was high voltage arcing. Basically, they were miniature lightning bolts. There was enough energy in those mini-lightning bolts to give you a nasty burn, so “electrocuted slightly” is probably the closest thing on your list. > [@SlackerInc](#): > > but I remember them doing one on the myth that microwaves cook from the inside out. What I like to say is that microwaves cook from the inside out from the outside in, which may sound confusing, so let me explain it. Microwaves generate heat inside the food by exciting molecules of water, certain sugars and fats, and a few other things. Since the heat is generated inside the food, this is the “inside out” part, and it is noticeably different than the heat from an oven, which cooks from the outside in. However, microwaves also penetrate into food from the outside, and they only go so far, and get weaker the deeper they go. So this is the “outside in” part. If you have a really thick piece of meat, it’s going to cook all around the outside and the inside will remain raw in a microwave (it also won’t brown, so it will be disgusting to eat in more than one way). So you put together the fact that the heat is generated inside the food, and yet the radio waves only penetrate so far, you get microwaves cooking from the inside out from the outside in. ETA: > [@Thudlow\_Boink](#): > > Has Mythbusters ever done anything with microwave ovens? They also did an episode where they tested whether a microwave with the door off could block a radar detector (spoiler - no, it couldn’t, and it’s dangerous to try it). ---
**Author:** ![SlackerInc](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/slackerinc/32/275_2.png) [@SlackerInc](https://boards.straightdope.com/u/SlackerInc)\ **Post date:** [October 5, 2015, 8:55pm UTC](https://boards.straightdope.com/t/is-it-dangerous-to-turn-on-an-empty-microwave/223175/31 "2015-10-05T20:55:41Z")
Nice explanation. ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [October 6, 2015, 4:34pm UTC](https://boards.straightdope.com/t/is-it-dangerous-to-turn-on-an-empty-microwave/223175/32 "2015-10-06T16:34:29Z")
> [@bbeaty](#): > > Oh boy, kitchen physics! > > I’ve been seriously abusing my own microwave oven for years with little harm. Generating fierce arcs and plasmoids. Shattering pyrex cups. Melting beer bottles. Making molten lava (from pumice or obsidian.) Hey there Bill! I don’t think I ever thanked you for pointing me toward the Dope. I have had many years of enjoyment both from this site and yours. In general it is not a good idea to run any sort of radio transmitter (microwaves are radio waves) without some sort of load. The power generated is going to end up somewhere, and if not into a matched antenna, or a meatloaf, it will end up heating something that wasn’t intended to withstand that. Often this will be the output amplifier or matching/coupling circuits. Without a load to dissipate power, it is possible for some of the energy to be stored in resonant circuits or cavities, and build up to destructive levels of current and/or voltage. As components heat, resistance increases and insulators may become partially conductive (glass, to repeat Bill’s example). ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [October 6, 2015, 5:04pm UTC](https://boards.straightdope.com/t/is-it-dangerous-to-turn-on-an-empty-microwave/223175/33 "2015-10-06T17:04:12Z")
I was once told that the door of a microwave oven had to be sufficiently strong to withstand an exploding egg. Whether they actually put an egg in a sample oven to test it, I have no idea. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [October 6, 2015, 5:37pm UTC](https://boards.straightdope.com/t/is-it-dangerous-to-turn-on-an-empty-microwave/223175/34 "2015-10-06T17:37:46Z")
> [@bob\_2](#): > > I was once told that the door of a microwave oven had to be sufficiently strong to withstand an exploding egg. Whether they actually put an egg in a sample oven to test it, I have no idea. I guess this one failed (fast forward to about the 50 second mark if you are impatient). [![](https://img.youtube.com/vi/6CqIZtMP98Q/hqdefault.jpg "egg blowing door open on microwave") ](https://www.youtube.com/watch?v=6CqIZtMP98Q) ---
**Author:** ![davidm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/davidm/32/225_2.png) [@davidm](https://boards.straightdope.com/u/davidm)\ **Post date:** [October 6, 2015, 10:23pm UTC](https://boards.straightdope.com/t/is-it-dangerous-to-turn-on-an-empty-microwave/223175/35 "2015-10-06T22:23:48Z")
> [@engineer\_comp\_geek](#): > > … > Your sci-fi light show was high voltage arcing. Basically, they were miniature lightning bolts. There was enough energy in those mini-lightning bolts to give you a nasty burn, so “electrocuted slightly” is probably the closest thing on your list. > … Is it to be expected that an empty microwave will throw damaging electrical arcs outside of it? That doesn’t sound like something that would be considered safe to have in a home. Surely there was something seriously wrong with this particular microwave, beyond being run empty, right? ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [October 6, 2015, 11:23pm UTC](https://boards.straightdope.com/t/is-it-dangerous-to-turn-on-an-empty-microwave/223175/36 "2015-10-06T23:23:11Z")
Oh yeah, that microwave was seriously futzed if it was arcing. Generally speaking, you can run a microwave for a short period of time and nothing exciting will happen. This is one of those “don’t try this at home” kind of things though, because it’s very harsh on the magnetron. Run it empty long enough and the magnetron will probably fail, and then you’ll probably get a really good light show, though it might be very brief. The arcing will also usually be contained inside the box. [Previous page](https://boards.straightdope.com/t/is-it-dangerous-to-turn-on-an-empty-microwave/223175.md?page=1)