Technical Evaluation
The active component in the Glowmark Boundary Marker Safety System is the lens containing photoluminescent crystals. These crystals have been specially treated with the result that they absorb light and then emit a soft glow for many hours afterwards. In practical testing, after only 8 minutes of exposure to daylight, a Glowmark marker will glow for 12 hours, i.e. more than enough to last throughout the night.
Scientific testing of the crystals within Glowmark was carried out in Germany and is detailed below.
Glowmark marker studs are guaranteed to perform for 10 years.
Scientific Testing
The Glowmark has been evaluated by the the German Institute for Standardization (Deutsches Institut für Normung e.V., or DIN) under their 67510 standard.
DIN
67510 Testing and Results:
All measurements of the Glowmark were taken in total darkness. It is
important to understand this distinction when trying to compare an
absolute DIN measurement with the apparent luminance perceived in
low ambient lighting. These differences in scientific luminance vs.
practical luminance are explained below.
A Glowmark was given an 8 minute exposure to a xenon source. The luminance value was then measured in millicandela per square meter (mcd/m2) and recorded against a time axis measured in minutes.
The DIN 67510 results for the Glowmark are as follows:
According to the DIN 67510 standard, a photo luminescence at or below .03 mcd/m2 is virtually undetectable to the human eye. For all intents and purposes, a photo luminescent pigment has stopped glowing at that minimal level. Extrapolation of the data suggests that the Glowmark reaches 0.3 mcd/m2 at approximately 4000 minutes, or 66 hours.
Scientific Luminance: Scientifically speaking, the Glowmark will glow for approximately 2 days and 9 hours (a total of 66 hours) after only an 8 minute exposure to natural daylight. If this photo luminescent "return on investment" is broken down into percentages, we see that the Glowmark has a laboratory efficiency of approximately 50,000%
Practical Luminance: Testing in a multitude of real world lighting conditions from night time to a heavily shaded tree-lined walking trail at noon, has revealed a perceived glow time less than the DIN 67510 result but still excellent. The Glowmark has an actual perceived, and therefore useful, glow cycle of about 720 minutes (12 hours) after only an 8 minute exposure to natural daylight. That is a practical efficiency of around 9,000%.
In other words, the Glowmark has stored enough energy to emit an easily perceived glow that will last throughout the night, including late evening and early mornings, after only 8 minutes in normal daylight. Therefore, any path or public area lined with the Glowmark will be clearly marked during these hours of darkness and can be safely traversed as long as the Glowmark is not removed or obstructed by debris.