Anytime I see someone mention hacking on magnetrons, I feel it my duty to remind us that the back of your eyeballs don't have pain receptors. If you were to power up thatagnetron outside of the microwave and point it at your face, it's possible you'd blind yourself before you even realized you were in danger.

Just wanted to add something. Itching is the first sign. If you feel itching in your eyes, turn the damn thing off immediately. I nearly blinded myself when I was an idiot undergrad. Kids, take the idiot adult's advice and don't play with it before you understand the theory and working principles extremely well.

IIRC, the danger is actually to the /fronts/ of your eyeballs, the result being cataracts rather than retinal damage.

And the front (cornea) has more pain receptors per surface area than any other part of your body. Not that this would necessarily help prevent cataracts if you expose your eyes to a magnetron.

I didn't realise this until I had laser surgery to correct a cornea problem. Oh dear, two days in a dark room on morfin, before I could even think straight again, no fun. But now I can see better again.

It's also a problem that there is no blood flow through your lenses. If you heat them via microwave radiation, they're going to stay hot for an alarmingly long time.

No doubt the material is toxic, but it doesn't seem breaking it would create a whole lot of dust, similar to any other ceramic. You'd have to machine or sand it.

http://en.wikipedia.org/wiki/Beryllium_oxide#Safety

Careful. ₄Be compounds are not your friend. Do not breathe or touch ANY beryllium dust - ever - at all.

If you're doing anything with it wear gloves; if you even might snap or machine it, you need to work in a fume chamber.

I read the Beryllium oxide page and found this interesting note:

   Formation of BeO from beryllium and oxygen releases the highest energy per 
   mass of reactants for any chemical reaction, close to 24 MJ/kg [1]

and this comment would be incomplete w/o sharing the findings of my wikipedia browsing which lead to making plasma in microwaves with grapes. https://www.youtube.com/watch?v=RwTjsRt0Fzo

[1] http://en.wikipedia.org/wiki/Beryllium_oxide#Safety

All roads lead to Rome.

I assume this article was posted because it was mentioned in XKCD[0] , which also ends on the grape plasma tangent.

[0]: https://what-if.xkcd.com/131/

When I was 12 I disassembled a microwave, unplugged from the wall, and got electrocuted. Not the visible kind like from static or from an outlet, but... I don't know how to describe it. Inside was a boxed case the size of a Kleenex cube, and my hand, palm side, just got sucked right on it like a magnet and bam I nearly passed out and fell off the chair. That was the end of playing with microwaves for me.