> > One simple example: turn on an empty microwave oven.
> > Because of reflections inside the heating chamber the thermal 
> > protection from the magnetron will be OFF in less than 3-4 minutes 
> > (100% continous power).
> 
> One thing I've always wondered. Pretty much every microwave 
> instruction says not to put metal into the oven -- yet the 
> whole oven is made of metal.
> I know that of course metal reflects rather than absorbs, but 
> it shouldn't do any harm (at least not as long as there is 
> enough other material in the oven). Or am I missing something?
> 
> Gerhard


If you put a spoon or fork in there it'll get hot after a few minutes.
That's about it.  Very thin metal (like in CDs) will get vaporised.
Something like aluminium foil won't, in fact some books say you can partly
defrost something by wrapping the bit you don't want defrosted in the foil.

Two bits of metal close together may produce arcs, as will foil crumpled up.
Or it may just sit there getting hot.  Something metallic that comes close
to the oven wall may arc too.

There are a few people trying to melt metal (like aluminium or silver) in
microwave ovens.  The focus seems to be to make a ceramic crucible that gets
hot enough for the melting to happen.

Most microwave have a couple of thermal cut-outs.  One is usually near the
magnetron itself, the other above the oven somewhere at the other end.  Tip:
don't test these by pointing a blow torch at them.  They go 'ping' and don't
really work after that.  Done it exactly once :)

Curing wood is something that's been done for a while.  A burning match or
candle is interesting.

Tony

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