An important part of sea kayaking is having the equipment necessary to allow one to signal for help in an emergency. There are many ways to call for help: radios, strobes, cell phones, flares, distress flags, night sticks, and dye marker are just a few. These can all be effective, but most are subject to battery or chemical exhaustion, may fail in marine environments, or have a limited range. A good signal mirror is a worthwhile addition to your kayaking equipment. It is inexpensive, weighs little, occupies less space than a wallet, and will work any time the sun is visible. A signal mirror can grab the attention of a potential rescuer at long range, and the sun is an inexhaustible resource.
Typically, the reflection of a 3 by 5 mirror is visible 20 miles, ground to air, in any direction with the sun high in the sky, and sometimes much farther – the record is 105 miles. As an emergency signaling device, the U.S. Coast Guard rates them second only to radios. U.S. and foreign military services have used signal mirrors for 60 years or so, and they have played a part in many rescues.
As with any safety device, signal mirrors have limitations. For instance, sunlight is necessary to operate the device (although signaling is possible on brightly moonlit nights, or by reflecting a rescuer’s searchlight). A general rule of thumb is that a highly reflective signal mirror can only be useful when the light striking it is strong enough to cast a shadow. On bright but overcast days a signal mirror will not be useful.
The effectiveness of the signal mirror is also dependent upon the kayakerís ability to use it. Aiming the device may be difficult if the paddler is injured or in heavy seas, especially if maintaining balance in the kayak is a concern. Aiming a signal mirror is more challenging, and the intensity of a signal decreases, if the sun is low in the sky and the potential rescuer is on the opposite horizon. Finally, signal mirrors are ”line of sight” instruments – they are only effective when your signal targets are not obscured by land, fog or the horizon.
Signal mirrors are most effective when flashed at a potential rescuer. A flashing light is more likely to capture the attention of a passerby, especially if the signal is weakened by distance, quality of the mirror, or low light levels. Flash the mirror by tilting it up and down across the target. Continuous flashing toward a moving object such as a boat or airplane would not be dismissed as a reflection from a naturally occurring source. Donít bother trying to flash a code message like an SOS. Not all of your flashes will hit the target, so any code is likely to be incomplete. Just concentrate on taking good aim.
On clear days, good signal mirrors can reflect light to targets that are too far away for you to see. If you see no potential rescuers, flash the entire breadth of the horizon; there may be someone out there who will see the signal.
Simple mirrors
Any flat reflective surface, such as a compact disc, a makeup mirror, aluminum foil, or even a shiny credit card, can be used as a signal mirror. Cases are on record in which items such as these have been used successfully. CDs as reflective devices reflect only about 20 to 25% as much light as a high-quality 3″ by 5″ plastic signal mirror. The reflective surface needs to be as flat as possible to increase the reflective surface area that is aimed at the potential rescuer. Otherwise, the projected signal may be too weak to be effective. For instance, if using a credit card, use the flattest one you have. Or if using aluminum foil, use the least ‘crumpled’ piece available and smooth it on a board or other flat surface. Convex- or concave-shaped materials will be less effective than a flat surface.
It takes two hands to use a simple reflective surface as a signal mirror. Hold the mirror close to your eye with one hand, with the reflective side facing away. Stretch out the other hand, and form a V with two fingers. Sighting over the mirror, (or, as in the case of a CD, through the hole), adjust the mirror to aim the sunís reflection through the V of your outstretched fingers and onto the plane, boat, shoreline, or other target. Flash the signal by moving the reflection up and down between the base of the V and the target centered between your fingers.
Better signal mirrors have features to aid in aiming the reflection. Some have sighting holes in the middle, others have aimers that make it possible to use the mirror with one handóessential if you need your other hand on your paddle to steady the kayak. Signal mirrors are available in several sizes and materials. Common sizes are 2″ x 3″, 3″ x 5″, and 4″ x 5″. The larger the mirrorís surface area, the more light it can reflect. For example, a 2″ x 3″ mirror has a surface area of 6 square inches, versus the 20-square-inch area of a 4″ x 5″ mirror. The drawback of a 4″ x 5″ signal mirror is that it is harder to hold and aim with one hand, storage is more difficult, and it may be more fragile. Materials include metal, glass, and plastic. Glass mirrors are the most reflective, followed by plastic, and metal as a distant third. An easy test to perform when comparing signal mirrors at the store is to look at your reflection in the mirror. If your image appears dim, distorted or diffused, look for another mirror.
Metal
Metal signal mirrors are the least desirable, and I donít recommend them. They can require two hands to aim, give a relatively weak reflection, will sink if dropped overboard, and some may corrode quickly. Metal mirrors can reflect as little as 14% of the light received, less if corroded. Even stainless steel models corrode, and lose a substantial degree of reflectivity.
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.
The test mirrors, from left to right: The Mark III glass mirror with aimer, the Star Flash plastic mirror with aimer, a simple metal signal mirror with center hole, the plastic Rescue Reflector with aimer. The top half of each mirror is reflecting a wire grid placed about 18 inches from the mirrors. The glass mirror (left), and the Rescue Reflector show the grid clearly and undistorted. The reflection in the Star Flash mirror is somewhat distorted. The reflection in the metal mirror is only slightly distorted, but very indistinct. Photo by Sea Kayaker Magazine
Reviews of Four Signal Mirrors
We evaluated the performance of several signal mirrors for reflectivity, durability, compactness, ease of use, and price.
Metal mirror
Metal mirrors without aimers are offered by several manufacturers, and are produced in a variety of sizes. In our study, we used a 3 x 4 chrome-plated stainless steel model. It reflected light was significantly less than that of any of the other products evaluated, and the reflection was very diffused. In terms of durability, this mirror resisted scratches and was virtually unbreakable. Stainless steel mirrors can resist corrosion far more effectively than carbon-steel models, which can begin to rust within a few days in a marine environment. This mirror did not come with protective packaging, however, lending itself to the possibility of scratching and collection of marine grime on the deck or in the cockpit of a kayak, further reducing its reflective properties. It came with a nylon lanyard, its only safeguard against sinking. In terms of compactness, this mirror is thin but heavy relative to other mirrors.
This mirror does not have a refraction aimer, so it requires the use of two hands to aim it at a target. The instructions are on waterproof paper glued to the back of the mirror. You aim this mirror by holding it with one hand at eye-level, and facing it to a point halfway between the sun and the rescuer. You hold your other hand 6-8 inches behind the mirror’s center hole and orient the mirror to reflect the spot of sunlight on your and. You then look through the center hole toward your target and angling the mirror until the reflection of the spot of light on your hand creates bright ring around the sighting hole. In practice, the bright round ring is not a ring around the center hole. Rather, it is the brightest spot anywhere on the side of the center ring. Since the bright spot is not visually superimposed on top of the target, you’ll won’t be certain that the signal is hitting your target. The complexity of aiming this mirror makes it impractical if you are on a moving platform such as a kayak.
Star Flash Signal Mirror (Plastic)
Offered by Survival, Inc, this mirror is standard issue for the U.S. Air Force. This mirror may also be sold under the ‘Ultimate Survival’ or (formerly) the ‘Gerber’ brands. It offers many advantages over other mirrors because it is lightweight, very compact, and inexpensive. However, the reflective power of the 2 x 3 model was only marginally better than that of the metal mirror. A permanently sealed plastic cover protects the mirror from the elements, but is itself very susceptible to scratching (more so than the other plastic mirror). Remember to store this device with its protective plastic adhesive sheet covering the mirror face. On the other hand, this mirror is very resistant to breakage. The mirror floats and has a hole for a lanyard. This product was submerged in salt water with no ill effects.
The aiming device is adequate, and works by refracting incoming light through retroreflective bead fabric; a bright spot forms in the center of the aimer when the signal reflection is on target. The aimer is not as effective as the other plastic and glass mirrors, however, because the bright aiming spot is more diffused and the bead fabric is thick, so I had difficulty looking past the bright spot to visually confirm that the mirror’s reflection is on target. The instructions are clear and concise, and are on the back of the mirror. The Star Flash mirror comes in a 2 x 3 model (0.7 oz, $8) and the 3 x 5 version (1.8 oz, $9)
Coghlan’s Survival Signal Mirror (Glass)
Imported from Japan by Vector 1, Inc, or sold under Coghlan’s brand name, these mirrors can be found in many sports retail outlets. They are constructed of two pieces of glass, one mirrored, glued together, with the aimer sandwiched in the center. In reflection tests, the 2 x 3 model was much brighter than the larger metal reflectors. It survived saltwater immersion, although there was evidence of some minor seepage around the lanyard grommet. The glass is more scratch resistant than the plastic products and metal products, but may break into sharp pieces when dropped, creating a potential safety hazard.
Coughlan’s mirror comes in a reusable foam pouch that provides some protection, but cannot be sealed from the elements. The pouch is too slight to prevent mirror breakage from a significant external shock. It is possible for the mirror to fall out of its pouch, and marine grime is not prevented from entering the pouch. A grommet is provided on the mirror as a lanyard hole. The mirror is very compact, but is much heavier than the Star Flash plastic model above.
The aimer is more effective than the Star Flash, however. Like the Star Flash, a bright spot forms through the center hole when aimed on the target. However, I could look past the reflected ‘ fireball ‘of light to get my bearings on the target. Also, the fireball seems less diffused than with the Star Flash, making aiming more accurate. Instructions are printed on the back of the mirror, but are in such small print on the 2 x 3 model and are written in red on a black background, making them hard to read. These mirrors are offered in the 2 x 3 model (1.5 oz, $9), the 3 x 5 model (3.6 oz, $11), and the 4 x 5 version (4.8 oz, $12).
Rescue Reflector Model 2 (Plastic)
Offered by Rescue Reflectors, Inc, the 3 x 5 model is our choice for the best signal mirror for sea kayakers. Its reflection was brighter than that of the glass mirror, although this may be an unfair comparison, due to its larger size. Part of the key to its reflective ability, however, may lie in the quality of its mirror – the reflected spot size from 85 feet was significantly smaller than that of any other mirror in our survey. As a result, more light was focused directly toward the target. Distortion and warpage of the mirror is minimized through aluminum reinforcement that is laminated between two layers of plastic. Each mirror is handmade, and is adjusted before final assembly to provide optimal performance.
A lanyard is permanently attached by epoxy. The back of the mirror has a red retroreflective back, to reflect a red signal under a searchlight at night. The mirror survived saltwater immersion; the device is sealed with synthetic rubber to prevent corrosion. Protective coatings applied to the plastic surface make the mirror fairly scratch resistant from (though less so than glass), and is unlikely to break if dropped because of the synthetic rubber coating on the edges and the foam added to its back. This foam also gives the mirror enough buoyancy to float. If the added bulk from the foam is a problem, Rescue Reflectors offers both plastic and glass models that do not float, but we recommend the floating plastic version.
A clear, resealable vinyl envelope protects the mirror from scratches and debris. The envelope contains an external eyelet that can be used to attach the mirror to a kayak deck or bag. The packaging includes two packages of antistatic cleaner, to clean the mirror in the field for improved reflectivity. The mirror is more bulky than the other mirrors tested, and it is also heavier than the Star Flash and the glass mirror. The aimer is very effective, making it easy to sight the target through the center of the mirror and direct the spot of light over the target. The instructions are concisely printed on the back of the mirror in white print that is easy to read on the red reflective background. More detailed instructions are added separately, on water-resistant paper. Pricing for the buoyant plastic models is higher than the other models tested for the 2 x 3 product (2 oz, $14), the 3 x 5 model (4.5 oz, $19), and the 4 x 5 version (6.8 oz, $25). The 4 x 5 model is U.S. Coast Guard approved.
Using a light-metered camera to gauge the brightness of the reflected spot at a distance of 85 feet. The metal mirror is used as a base line, and the others are on a line showing the number of times brighter than the metal mirror.