Re: (NDC) Perplexed By My Lunch


"marklaw" <mkalina@xxxxxxxxxxxxx> wrote in message
news:632dbe46-7ee5-4607-9b62-4085e71fc29f@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

It's an old wive's tale.

Do you think Big Brother would allow them to be sold if accidental
nuking of metal scrap or aluminum foil could cause a dangerous
condition? Metal containers are discouraged from use in microwave
ovens only because microwaves cannot penetrate metal, resulting in an
inconsistent heating process. The instructions on your soup probably
tell you to stir and let rest after nuking, and that is to compensate
for the shielded areas of the container.

http://www.gallawa.com/microtech/metal_arc.html

When metallic objects are indiscriminately placed in a microwave oven
cooking cavity, the energy pattern becomes disrupted and distorted. This
condition produces arcing. When two metal objects, such as a metal bowl and
the [metal] cavity wall, are placed in close proximity and subjected to an
intense field of microwave energy, arcing will result. Arcing occurs
because the air between the two metallic objects becomes electrically
charged, just as the air between a thundercloud and the earth becomes
charged or ionized. This ionized air becomes an electrical conductor, and
electric current then leaps the gap like a small bolt of lightning.
However, lightning only lasts for an instant because it discharges or
neutralizes the ionized air, but an arc in a microwave oven will continue,
to a greater or lesser degree, as long as the microwave energy is applied.
At the very least, this can cause marring or pitting of involved surfaces,
and at worst, can burn a hole right through the cavity wall.

http://amos.indiana.edu/library/scripts/metalmicro.html

As its name implies, a microwave oven uses intense microwaves to heat and
cook food. Like any electromagnetic wave, a microwave consists of electric
and magnetic fields. When the strong microwaves produced by a microwave oven
interact with a *** of aluminum foil, their electric fields cause the
mobile electrons in the foil to accumulate at the ***'s sharp, pointed
tips. This build-up of electrons creates a strong electric field in the
surrounding air. When the electric field becomes strong enough it causes
free electrons in the air to accelerate and jar loose more electrons from
gas molecules in the air, which then go on to jar even more electrons loose.
This chain reaction creates an electrical charge in the air, which shows
itself as sparks. Although rounded metal objects such as spoons are less
likely to create sparks, the safest bet is to avoid putting any kind of
metal in the microwave.

http://en.wikipedia.org/wiki/Microwave_oven

Any metal or conductive object placed into the microwave will act as an
antenna to some degree, resulting in an electric current. This causes the
object to act as a heating element. This effect varies with the object's
shape and composition.

Any object containing pointed metal can create an electric arc (cause
sparks) when microwaved. This includes cutlery, aluminium foil, ceramics
decorated with metal, and most anything containing any type of metal. Forks
are a good example. This is because the tines of the fork resonate with the
microwave radiation and produce high voltage at the tips. This has the
effect of exceeding the dielectric breakdown of air, about 3 megavolts per
meter (3×106 V/m). The air forms a conductive plasma, which is visible as a
spark. The plasma and the tines may then form a conductive loop, which may
be a more effective antenna, resulting in a longer lived spark. Any time
dielectric breakdown occurs in air, some ozone and nitrogen oxides are
formed, both of which are toxic. Microwaving food containing an individual
smooth metal object without pointed ends (for example, a spoon) usually does
not produce sparking.

The effect can be seen clearly on a CD or DVD. The electric current heats
the metal film, melting the plastic in the disc and leaving a visible
pattern of concentric and radial scars. It can also be illustrated by
placing a radiometer inside the cooking chamber, creating plasma inside the
vacuum chamber.

Several microwave fires have been noted where Chinese takeout boxes with a
metal handle are microwaved. Twist ties containing metal wire and paper are
also notoriously dangerous.


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