wrote in message
...
"Glass cored resistors cause an increase in current and consequently the
potential for damage"

I remember a video on the internet about having some "fun" with a
microwave. Normally you put glass in a microwave it is unaffected. Well
they took a torch to it and heated it up first and then it was definitely
affected by microwaves. Before that I never knew glass becomes conductive
at high temperatures.

Most types of glass are lossy enough at microwave to not need any such
preparation.

Once I put a TV valve (tube) in the microwave, the glass glowed red and
became plastic, it wrapped around the internal structure like cling film.

My coffee mug is glass - I have to tuck the handle into a corner when I heat
a cup of water, otherwise the handle gets hot and burns my hand.

The alumina ceramic on a spark plug is also lossy enough to get red hot.