I wanted to write about a commonly available, very small bit of kit which many people may overlook as a useful survival tool, the mirror. Yes, the plain old mirror, or more generally any shiny reflective surface, can save your life, and in fact has saved many lives. How? Basically, by reflecting sunlight.
A signal mirror or heliograph (literally sun writer in Greek) is one of the oldest and longest distance signaling devices in history. Flashlights are great for directional light, but there are very few lights on Earth brighter than the sun. The signaling mirror's military usage dates back to the ancient Greeks who used the highly polished insides of shields to signal distant formations to coordinate maneuvers. Distance-wise, the farthest documented use of a signal mirror which led to a rescue in modern times is an amazing 150 miles.
A mirror is simply a reflecting surface. A good survival mirror can be composed of many things. Silvered or aluminized glass, Lexan laminates, polished metal. Composition varies by intended purpose.
Many people EDC mirrors on their person for cosmetic purposes. Mirrors can be found on almost any vehicle. Flexible sheets of Mylar make great mirrors until they get scratched up, and in fact, I carry a business card sized piece of Mylar in a protective sleeve in my wallet (as a portable emergency mirror). Also, just thinking outside the box a bit, flat and/or spinning parabolic mirrors can be made with liquid mercury.
It logically follows that the larger the reflecting surface the more sunlight is redirected. The larger the better, is a rule of thumb. The lighter the colour the better also (like white reflects better than black). Remember almost any flat, shiny surface can be a reflector, not just actual mirrors. Windows from cars, boats, and aircraft, glass from picture frames, poster covers, clock faces, shiny cookware and polished silver platters, any flat sections of stainless steel, brass and aluminum, CD jewel cases, window panes and glass doors from houses, and glass table tops can all be good directable sun reflectors.
I have found that CDs themselves and aluminum foil do not make effective reflectors. In a pinch of course, they are better than nothing. The plastic of CDs is not smooth enough, plus the aluminized CD media section is designed to reflect light (laser light) at oblique angles. Aluminum foils no matter how much you smooth it just never gets flat enough or crease free enough to be reliable reflectors.
Many very good survival mirrors can be purchased at sporting goods, camping, outdoors and surplus stores. REI.com stocks several different sizes and models. I personally recommend getting the largest mirror that your personal BOB can efficiently hold. In most cases, that might be the 4" X 5" size. Additionally, though they are more prone to scratching, I prefer the Lexan laminate composition mirrors to the glass or metal mirrors, mainly because of weight savings and shatterproof durability. Finally, most designated signaling mirrors (heliographs) will have a center aiming hole and I find them to be a useful feature. By looking through the aiming hole, an artifical dot can be seen which indicates exactly where the sunlight is being reflected. My chosen survival mirror even makes the aiming dot a red colour for ease of sight. Finally you might want to consider certain accessories and adjuncts as value added, like a lanyard hole and lanyard (to keep it from falling/breaking), a flotation device (to keep it from sinking to the bottom of the ocean), and a protective case or sleeve (to keep it scratch free) as desireable extra features.
Even without an aiming hole, the use of a signal mirror is easy. First you are somewhat limited by the position of the sun and any intervening obstacles (trees, terrain features), but basically, choose a target, hopefully on the same side as the sun. Hold up the mirror and try to reflect a beam of sunlight down at your feet. Next, sighting the intended target (a distant plane, boat, or Ranger station) hold up two fingers in a "V" and sight the target between those fingers. With the other hang that is holding the mirror, bring the reflected sunlight beam up until it shines on the two upraised fingers. Play the sunlight beam side to side and up and down across the two fingers. To the observer, it will appear like a brilliant pinpoint flash of sunlight. Note: an intermittent flashing is much more likely to draw attention than a solid constant reflection, which might be a natural occurence. If you are close enough to know that you are precisely hitting the target, like an aircraft, you can try to send a message in CW. Combinations of three (blasts on a whistle, rifle shots)are an internationally recognized distress signal. ... --- ... (dot dot dot dash dash dash dot dot dot) is "S.O.S.". Even if you don't ever learn the rest of the Morse alphabet, this combination may be a good one to memorize and practice.
I have incidentally found mirrors useful throughout my life as a tactical periscope, that is to look over, under, around obstacles and corners. In fact, one of my best inventions is a tactical mirror for the M-4 RIS, M-203, and M-16 series. In some situations it is just smarter to look around a corner with a small mirror than it is to stick your head out. I still use an adjustable telescoping mirror for geo-caching searches (which simply saves me from sticking my hands into yucky spider web covered holes and crevices... LOL).
Additionally, mirrors, duh... have myriad uses as..... mirrors. What I mean is, among other things, they are very useful for "visualizing" yourself. Afterall, there is over half of your own body that even you yourself have never seen directly, and not all injuries and problems will conveniently occur where you can see them in a survival situation or medical emergency.
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