Frequently Asked Questions
What is Photoluminescence?
Photoluminescent materials (commonly called “glow-in-the-dark”) can absorb and store direct light energy (sunlight, fluorescent, incandescent, etc.) and emit that light energy when there is no longer a direct light source. When ambient darkness occurs, it becomes highly visible, lasting from a few hours to several days depending on the quality and color.
Upon removal of the light source, the stored light is gradually released, the strongest glow is produced during the first 30 minutes of darkness, the most critical period following a power failure or other emergency. It then fades over a period until reintroduced a direct light source, so it may store energy again. This means the photo luminescence process is “circulatory”.
The bases of most photo luminescent products are photo luminescent pigments that can be incorporated into powder coat, paint, ink, fabric, ceramic glaze or porcelain enamel, glass, flexible and rigid molded plastics. Typical products include self-adhesive flexible vinyl tapes, rigid PVC marker strips, and silk-screened signage. Photo luminescent fabric, enamel-coated sheet metal, and ceramic tiles are also available.
How bright are these glow products?
Many manufacturers refer to the extinction time of their products, which is defined as the time required for the afterglow to diminish to one masb (0.032 mcd/m2, or about 100 times the limit of human perception). In practice, this is very difficult to see unless your eyes are fully dark-adapted, and you are in a completely dark environment.
For practical purposes, luminance of one to two millicandela’s per square meter are more appropriate limits for life safety applications, and even this assumes a smoke-free environment. Thus, zinc sulphide products are useful for perhaps only 30 to 45 minutes after their excitation source has been extinguished. The afterglow of strontium aluminate products, on the other hand, can be visible for several days, sometimes more. All Techno Glow powders are strontium aluminate based unless otherwise specified.
Strontium aluminate products can provide surprising amounts of initial afterglow. For example, a four-inch square of excited material held a few inches away from a magazine page can provide enough light to read by for the first minute or so of afterglow. Micro-prismatic retro reflectors and other brightness enhancing techniques can increase the materials luminance by several times.
Can Photoluminescent products replace traditional emergency lighting?
Light lead photoluminescent materials were originally designed to complement existing emergency lighting systems but continuous improvements in luminance performance mean that in certain circumstances, such as a power outage, high quality photoluminescent products may replace emergency lighting. They can be sited at waist or skirting level, so they can still function if the ceiling lights become obscured by smoke. Similarly, lifesaving appliances and firefighting equipment become more visible and are easily located in an emergency. Some emergency lighting can take up to 15 seconds to activate. In these instances, photoluminesce products will light up immediately.
How do the materials work?
Techno Glow photo luminescent materials contain purpose designed inorganic phosphor compounds that are energized in seconds by the ultra violet and blue light wavelength energy that is present in nearly all light sources. This high-energy source is converted into a lower energy source of light. The lower energy light source is yellow-green, the color most readily perceived by the human eye and as specified by safety signs standards. Techno Glow photo luminescent materials are non-radioactive, non-toxic, and provide a strong light source. They are also self-extinguishing, so they carry on working when they are most needed.
Photo luminescent materials differ from reflective materials, which amplify and increase relative brightness when light is applied. Fluorescent materials are quite different from photoluminescent materials. Fluorescent materials (such as the 3M fluorescent work zone film or a “hot pink” tag) borrow light energy in nearby wavelengths and concentrate the amount of light returning to the viewer in a certain (for example, day-glow orange) wavelength. Fluorescent films are especially useful in dawn and dusk viewing times, when they appear particularly bright. Photoluminescent materials require prior exposure to a light source to glow in the dark.
Is it environmentally friendly?
Photo luminescent materials are non-toxic, non-radioactive and contain no phosphorus, lead, or any other hazardous chemicals.