If you built a coffin size microwave oven, how long would it take to kill a human being in it? To incinerate the body?
I’m writing a story, folks.
Incinerate? As in reduce to ashes? Never. Microwaves are absorbed primarily by water, and to a lesser extent by fats, oils and sugars. Heating something like a ham or a human body drives off water, and melts out fats, thereby reducing the rate of MW absorption. Eventually, there would reach a point - well below the combustion temperature - where the temperature of the object beign cooked will no longer increase in temperature. There might be some - perhaps even considerable - localized exterior burning, but nothing approaching a complete reduction to ash.
As for killing, that would depend mostly on the power output of the oven. I imagine the primary mechanism of death would be heat destruction of brain tissue. Since fevers exceeding about 107 degrees F are often fatal if untreated, I assume exceeding this by much will lead to death fairly quickly. For a typical 1 kW magnetron, this would take on the order of 10-20 minutes, assuming a human head has roughly the same absorption as an equivalent mass of water. Of course, the body absorbs much of the radiation, too, so you’d need to increase this figure, by say 3-5 times, depending on body weight. This figure would decrease depending on the RF power. If you give some specifics, like power, body mass whether it’s a fat or lean person, I can calculate a better approximation for you.
That’s not always true. I once attempted to dry out a wet paperback in a microwave oven. I left the kitchen for a little too long, and when I returned, the book was aflame.
I suppose the surface carbonization could provide circuit paths, leading to large current heating. Was there ny metal, like staples, in the book? I’m still not sure that can happen to flesh, at least not to the extent of completely reducing a body to ash. Anyone got a spare ham, say a 10-pounder, they can nuke, in the name of science? 
I’ve certainly burned the crap out of microwave popcorn. Finding out things can’t burn in a microwave is something of a surprise.
Heyyyy, maybe somebody switch the element in my microwave for a…
you guessed it…
1920’s Style Death Ray!!
There’s a piece of material on the bottom of the bag that’s designed to absorb microwaves and get hot - similar to the “crisping sleeves” you get to use for some products. That’s where you’ll get the most significant burning. I don’t know if it will buarn much, otherwise, but I can’t say I’ve actually tried. Burnt popcorn stinks!
No metal. There could have been salts in the puddle the book fell in. That could dry down to form little conductive areas. All you’d need is an arc or two between adjacent conductors, and you’ve got a burning book. Electrolytes in a body, or a ham, might do the same thing as the water is eliminated.
True enough, though these effects tend to be localized. I’d experiment, but unfortunately it’s not my microwave oven, and the owners might get upset if I tried to incinerate a ham in it. Heh. Otherwise, I’d totally do it.
Now I’m really curious…I got me some unwanted meat back home in the fridge right now. My wife can’t stand the sight of rare flesh, and she always ruins my steaks by, you know, cooking them. She’s got a show tonight. I get home from work…do a little “research”…liberal use of Fabreze afterward to disguise the evidence…do I dare try it??
You must, in the name if fighting ignorance!
In all seriousness, the experiment is not without risk, including fire and damage to the oven. If you do decide to do it, do it outside - or at least in the garage - and keep a fire extinguisher handy, and be prepared to disconnect power at the first sign of danger. In particular, under certain conditions, a small, smoky flame can result in a rather spectacular phenomenon called a plasma ball. This is an extemely hot ball of ionized gasses similar to ball lightning, which can easily burn the finish on the inside of the oven, as well as melt and scorch any plastic bits it encounters.
Don’t try this at home, kids.
OK, thanks for the tips. I do have a microwave in the basement that is old and unused. But I live in a townhouse…if somebody next door saw me standing outside, next to a microwave hooked up to an extension-cord, wielding a fire-extinguisher…
Meanwhile, attempting to research this on the net has turned up all kinds of fun stories about jet-propelled exploding grapes, plasma balls of the kind you describe ( only generated deliberately), mutilated compact disks, homemade Tesla coils, Peep torture; but I can’t find anything on incinerating corpses or other large hunks of meat. Go figure.
For goodness sakes, don’t forget to remove their fillings and any metal jewelry! You don’t want to ruin the microwave, other people have to use it, you know.
And poke holes in them, first!
First of all, thanks to everyone for their replies.
I have been in an office nothing but a space heater all day, and while nuking my coffee for the upteenth time, I thought about how nice it would be to have a microwave big enough to get warm in, cause I’m dying here. Hence the idea.
I don’t think that this is true.
Because, well, [SECOND-HAND ANECDOTE]my sister once microwaved a cat. She was curious and wanted to see what would happen. She only had it in there for a few seconds and it seemed fine immediately afterwards. However, next morning, it was found on the kitchen floor with its innards spilled out.[/SECOND-HAND ANECDOTE] I don’t know how exaggerated this is because, I hadn’t been born when this happened. My sister has not become a serial killer since.
If you have (or can acquire) a suitable Pyrex container to use, I highly recommend doing the plasma ball thing. If you follow all the safety precautions, you can do it indoors. Don’t let it run for more than about 30 seconds, or so. It really is visually spectactular.
** Annie-Xmas** --I know it’s cold up North, but really…I doubt Donner Party measure are needed, and if they are, I recommend a slow conventional oven & orange sauce.
Really. The skin doesn’t get brown and crispy the way I like it from cooking in a microwave.
And as an aside to Strinka, I’ll bet people have noticed you now. 
Somewhat off topic, but I think I may try smelting some silver in my old microwave as described here, microwave melting of metals
There is a trick involved:
Apparently, you can use the technique to melt up to 250 grams of Iron (1535°C) in an 850 watt oven!