Glass
Glass signal mirrors give the strongest signal for a given size, and
are available with one-hand aimers. They reflect nearly 100% of the
light received. They also have the best scratch resistance. They do,
however, have some disadvantages. They are heavy, and will sink unless
attached to a source of buoyancy, which increases bulk. Unprotected,
they will break upon impact with a hard surface, and protective shock-resistant
packaging also increases bulk. Most glass signal mirrors have an aimer
laminated between two pieces of glass. If the edges of the lamination
aren't well sealed, the mirror is unsuitable for use in marine environments.
If water penetrates the lamination, especially likely if the glass
is held together with strips of double-sided adhesive tape, the aimer
will be inoperable.
The better glass signal mirrors have nearly full-face adhesive sheet
lamination, and edges sealed against water entry. To check a glass
mirror for type of lamination, look at its corners for gaps or flaws
in the seal.
Plastic
The reflectivity of plastic mirrors is not as good as that of glass
mirrors, but they are lighter and are resistant to breakage. The
best seagoing plastic signal mirror designs actually float. They
produce a strong degree of reflectivity, although not as strong
as that of the same size glass mirror (up to 70% of the light received,
depending upon the quality of the device). These higher-quality
plastic signal mirrors have one-hand aimers, allowing the other
hand to balance a kayak in waves. Plastic is more easily scratched
than glass and apt to lose reflectivity if mishandled. Good plastic
signal mirrors reduce scratches through the use of either a clear
abrasion-resistant coating, an adhesive-backed reusable shield,
or a protective case. While plastic signal mirrors have a number
of advantages, not all of them perform well. There are a number
of rather poor plastic signal mirrors that have poor or nonexistent
aimers or excessive warping, which spreads the reflection and weakens
the signal.
Aimers
Signal mirrors with aimers project a bright spot through the
center hole when the reflector is on the target. This is accomplished
from redirected reflection of the light source via small glass spheres
partially coated with metal and adhered to a metal grid or cloth
disk in the center hole. The aimer is sandwiched between the two
pieces of glass or plastic that make up the mirror. The reflection
of light within the glass spheres diverts some light in the direction
opposite that reflected by the mirror. With a little practice, you'll
soon become adept at finding the target and quickly putting the
light spot into the center hole and on the target without the use
of a second hand. If this proves to be difficult, first reflect
the sun onto your outstretched hand, then slowly bring the back
of the mirror to your eye, while maintaining the reflection on your
outstretched hand. Look through the center hole, find the reflection
on your hand. You'll see the bright spot created by the aimer. Lower
your hand and put the light spot on your target.
When
shopping for a mirror, look for one with a mesh aimer around the
center hole. Lower quality mirrors may have a center hole, but exclude
the aiming technology. This is true of metal signal mirrors. Using
metal mirrors requires two hands, and a lot more practice. Some
of these designs create a bright ring of a reflection around the
center hole when the target is acquired, but it is sometimes necessary
to use a second hand to shade the back of the mirror to see the
ring. If you are in waves of any significance, using metal mirrors
may be too difficult.
Prices
for high quality glass or plastic signal mirrors range from $12
to $32. For some of the glass mirrors, shock-resistant and buoyant
packaging is included. For a plastic mirror, make sure you have
an envelope or case to keep the mirror clean and protect it against
scratches.
How
to use signal mirrors
After you've purchased a signal mirror, don't just pack it
into a survival kit and forget about it. Go outdoors on a sunny
day and practice using it. This is far better than trying to learn
the technique under actual emergency conditions. In about 15 minutes
you can become proficient in finding the aiming spot and reflecting
the mirror onto a distant object. Don't practice while you are out
on the water unless you are quite sure the targets you are aiming
at will not read the flashes as a distress signal.
Never reflect sunlight toward a vehicle, plane, or person at short
range.
This can cause momentary blindness and result in an accident.
As part of your overall safety strategy, you should acquire a good
signal mirror, learn how to use it, and bring it when venturing
out on the water. When the conditions are right, a signal mirror
is an effective distress signal with a very wide range.
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