A signaling mirror is a simple, effective means of communication and an indispensable item in your every day carry bag. We’ll review two brands of signal mirror — the Adventure Medical Kits Rescue Flash, and the Ultimate Survival Technologies Star Flash.
Why use a signal mirror
On a clear, dry day, a signal mirror can project an attention-getting signal as far as 15 miles. And if you’re looking for the signal, expecting it, you can spot it up to 20 miles away. Rescue teams, first responders, air and sea pilots, and military personnel are all trained to recognize intentional reflective signalling as a distress call. In addition, there’s a large community of
preppers, survivalists, boy scouts, retired servicemen, hikers, campers, and on and on, all of whom will react to a signal mirror. Put all that together, and you’ll see that a signal mirror is a highly effective means of getting yourself noticed, particularly if a search and rescue is on, but even if it’s not.
Any reflective object can be used, but signal mirrors are designed to make targeting your flash a lot easier. They have a hole in the middle with a retroreflective surface that allows you to train a bright indicator on your target, so you’ll know for sure that you’re shining in the right place.
Geek bonus: How the retroreflective surface works
Most retroreflectors we’re familiar with are the kind that reflect light back to the source — we see these on automobile tail lights, road signs, and safety clothing. The mesh material in the mirror’s central hole is a type of retroreflector; it reflects light through the hole at an angle that is supplementary to the sun’s angle of reflection on the mirror. (The angle of reflection is equal to the angle of incidence, but lies opposite the surface normal). That causes
some light to shine into your eye in a direction 180 degrees opposite the direction in which the mirrored surface is projecting its signal. The practical result is that when you see a bright dot superimposed on the horizon, a house, a plane, or your hand, you know that that’s where the flash will be seen. Because the mesh is rather coarse, there is a lot of empty space through which light is transmitted normally as well, so you can also see the world through the hole as it really is. In short, the retroreflective material allows you to co-witness the dot and the target. Finally, the retroreflective material attenuates the sun’s light, so the indicator dot doesn’t damage your eyes.
Description of the signal mirror
The Rescue is 2″ by 3″ and the Star is 3 x 5, but it also available in the smaller size. Both are made from Lexan, a brand of polycarbonate plastic that is very tough, but not very hard. It won’t break, but it will scratch, which diminishes its reflective ability. You should protect your mirror by keeping it in a plastic sandwich bag.
Both mirrors come with printed instructions on the back, both have lanyard holes, and both have a retroreflective aiming aid in the center.
The Star’s retroreflective material is a relatively opaque white material which is more difficult to use than the one on the Rescue because you can’t see your target as easily. The Rescue’s retroreflective material is far more transparent. This doesn’t matter in high-contrast situations, like if you’re aiming at an object in a clear sky or on the horizon, but if you’re trying using the Star to signal a house down in the valley, you might have a hard time spotting it. It’s not by any means impossible, it’s just harder than with the Rescue.
The Ultimate Survival Technologies web site advertises that the Star mirror will float, but when I tested it, it sank. I contacted the company, and they explained that only the smaller, 2 x 3 model actually floats, although at publication time this was not specified on their web site.
How to use the signal mirror
WARNING: Don’t shine the mirror directly into anyone’s face unless he’s a mile away or more!
Put the mirror up to your face with the aiming circle about one inch from your eye, and look through the hole (but not directly at the sun, of course!).
Reflect the sun onto a nearby target, like a boulder or even your hand. When your eye is in line with the target and the aiming hole, you’ll see a bright spot on the retroreflective surface.
Now move the mirror toward the object you want to signal, whether it’s a boat, a distant house, or an airplane. As you move, keep the bright spot in view, and when the dot is on your target, the reflection will be too.
Whichever one you choose, we found the smaller mirror to be just as effective as the larger one at generating an attention-getting signal at 1.5 miles. There might be a noticeable difference at greater distances, but we didn’t test this. Because the Star has a retroreflective surface that makes it more difficult to find the target, I prefer the Rescue Flash.