Why Add Retroreflective and Photoluminescent Technology to Your Designs
For ultimate visibility in darkness, two technologies are recommended to be combined: retroreflective and photoluminescent. Each one has an important purpose and they actually work in opposite ways from the other. When used in tandem, you get the benefit of both options covering all conditions.
Retroreflection requires a straight source of independent light to hit a reflector target. Instantly the light reflects back in a very narrow angle with minimal scattering. For example at night when car headlights shine on a jogger wearing retroreflective patches, the driver sees a sudden flash of light clearly showing the jogger straight ahead. It works well in both dark and low light conditions. However the reflective light shines only toward the light source, in this case the car driver. Someone bicycling toward the jogger from a different path would not see the reflective light when the headlights hit those reflective patches.
Retroreflective materials typically consist of glass beads, microprisms or encapsulated lenses that are sealed or coated onto a fabric surface, or they might be embedded in a plastic substrate. The beads reflect light like millions of tiny mirrors. It’s distinctive and noticeable as long as the light keeps hitting the target. As soon as the light source is past the target area, all reflected light immediately ceases. There is no gradual decline.
There are three ways to enhance the brightness of reflective light. It always appears brightest when you are closest to the originating light source, therefore a longer strip of lighting would help widen the viewable area. Secondly, the brighter the light source, the brighter the reflective result. So as a spotlight or car headlight gets closer to the object while still hitting it, the reflective brightness increases. And finally increasing the surface size of the reflective target will also produce a brighter result.
The main key to remember with retroreflective technology is that optimal glow is achieved when the observer’s eye and the light source are closest. It cannot be observed if viewed from side angles to the source light.
Photoluminescence or Glow in the Dark technology delivers a bright glow in the absence of light, or full darkness. This is completely opposite to retroreflective material which requires light to succeed. When a light source shines on photoluminescent material, it starts to charge by absorbing the light energy. The energy continues to be stored while the light is present. As soon as light is removed, and the material glows brightly in the dark.
Glow in the Dark materials work best by charging under sources with strong UV waves such as sunlight, indirect daylight, direct room lighting or black lights. Exposure to UV lighting for just 5-30 minutes will fully charge most photoluminescent materials allowing them to glow in darkness for 8 or more hours.
Unlike retroreflective materials, glow in the dark can be seen from every angle. This would benefit the jogger to be seen by the bicyclist, not just the car driver. Additionally the glow is continually viewable in the darkness, not dependent on a source light to make it viewable. Similar to retroreflective, the closer you get the brighter the glow appears. However when a headlight or searchlight shines directly on photoluminescent materials, the glow immediately ceases, just the opposite of retroreflective materials.
There are ways to enhance the glow. Brightness can be enhanced by the surface size of the photoluminescent material. And although high performance glow is available in several colors, green glow is the brightest to the human eye and this is why it is used for most for safety and emergency conditions.
The Perfect Combination
To achieve optimal visual safety, using a combination of both retroreflective and photoluminescent technologies is recommended. This provides the double function of greatest visibility using reflected light sources, as well as during fully darkened situations.
Lunabrite offers HiViz Duo Safety Patches that pair both retroreflective and glow in the dark technology in the same product. HiViz patches provide better visibility to keep you safer at night, no matter what the conditions.