Many food items have a thin layer of metal or iron filings in the
package.

Modern microwaves limit current and some abort.

Older ones burn off the gold ring on bowls and coffee cups nicely(or badly).

New ones - I have an inverter power supply - my wife can carry the unit
from counter to another for cleaning... The old one finally bit the dust
after 27 years of good service. It worked to the last day. So many modern
settings and abilities we bought this new one.

If you buy some meals - they often have a heating pad - ferrite or such
in the bottom to pop the corn or such.

I suspect the Aluminum is an alloy and is of higher resistance. The plastic
is likely there to keep it save from the touch...

The microwave is sourced, and when a short is seen the current draw on the
signal (impedance loss due to loading) draws current. If the unit is modern
then it senses the current and backs off on the power. Saves itself. Saves
the vendor from trouble.....also.

Martin

erngineman wrote:
Yesterday at a yardsale I saw a pressure cooker made to be used in a
microwave oven. Out of curiosity I bought it for $5.00
It seems to be made out of plastic coated aluminum. In fact it was
made by Northland Aluminum Products inc.
I always thought microwaves were blocked by electrical conductors,
also I've read about problems caused by microwaving food wrapped in
aluminum foil.I tried it and it works quite well.
I'm wondering what the secret is?
Engineman