– 4 –
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 conduction.
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
Refl 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 refl 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 High
. 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 microwave
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 heating. 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.
F0003BA30QP.indd 4
F0003BA30QP.indd 4
2011-7-4 10:07:23
2011-7-4 10:07:23
