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Microwaves and How They Work
Cookware and Utensils Guide
Microwaves are a form of high frequency radio
waves similar to those used by a radio, including AM,
FM and CB. They are similar to a television where
the radio waves are converted to a picture on the
screen. However, microwaves are much shorter than
radio waves; approximately twelve centimetres wave
length. Electricity is converted into microwave
energy by the magnetron tube (which is the heart of
the microwave oven).
From the magnetron tube, microwave energy is
transmitted to the oven cavity through a small
plastic covered piece. The microwaves are converted
to heat in the food. The microwaves enter from the
outside of the food and travel through the food losing
half of their power every two to three centimetres.
Continued cooking to the centre occurs by conduc-
tion.
Although pacemakers used to be affected by
microwaves (as well as by other radio waves), they
are now shielded and are not bothered by these
interferences. This allows people with pacemakers
to sit calmly by their radio or television and cook with
microwave ovens.
When microwaves come in contact with a substance,
any one or combination of three things may occur.
They can be:
1. REFLECTED
2. TRANSMITTED
3. ABSORBED
Re
fl
ection:
Metal substances REFLECT microwave energy and
because there is no absorption, there is no heating.
This is why the oven interior is either stainless steel
or epoxy-coated steel. This ensures that the
microwaves are kept inside the cavity and evenly
distributed throughout the food with the help of the
turntable.
Transmission:
Such substances as paper, glass and plastic
TRANSMIT microwave energy and do not become
hot except from food. Because these substances
do not re
fl
ect or absorb microwave energy, they are
ideal materials for microwave cooking containers.
Absorption:
Food contains moisture and will ABSORB
microwave energy, which causes the moisture
molecules within the food to vibrate at an incredible
rate (2,450,000,000 times per second). Friction,
created by the vibration, produces heat energy which
is conducted throughout the food.
It is important to use the correct container when
cooking in a microwave oven. The following will help
you make the right selection.
How to Test a Container for Safe
Microwave Oven Use
TO TEST A CONTAINER FOR SAFE MICROWAVE
OVEN USE:
Fill a 1-cup glass measure with cool
water and place it in the microwave oven alongside
the empty container to be tested;
heat one (1)
minute at P10
. If the container is microwave
ovensafe (transparent to microwave energy), the
container should remain comfortably cool, the water
in glass measure should be hot. If the container is
hot, it has absorbed some microwave energy and
should NOT be used. This test cannot be used for
plastic containers.
Paper Products and Freezer Wrap
Waxed paper, paper plates, cups and napkins should
not be used for heating or cooking food. Freezer
wrap should not be used as it is not heat resistant
and may melt. Paper towel, greaseproof paper and
bake paper may be safely used for short periods of
time for covering or lining.
Glass, Ceramic and China
Heat-Resistant glass cookware
is invaluable in
microwave cooking. Many of these items are readily
available in most homes: glass jugs, mixing bowls,
loaf dishes, covered casseroles, oblong baking
dishes, pie plates and round or square cake dishes.
Examples of this type of cookware are Pyrex® and
Corningware®.
Dinnerware
can be used for microwave heating.
Many brands of dinnerware are microwave safe.
Check the care information for reference to mi-
crowave use for dinnerware and serving pieces. If
dinnerware is marked ovenproof, it frequently is safe
to use in the microwave oven. However, to be sure,
check by conducting microwave dish test previously
mentioned.
Several types of glassware and dinnerware
are
not recommended for use in the microwave oven. Do
not use dishes with metallic trim or containers with
metal parts. Do not use cups or mugs with glued on
handles, as they may fall off with continued heat-
ing. Do not use delicate glassware. Although the
glassware may be transparent to microwave energy
the heat from the food may cause the glassware to
crack.
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