Here's the science on why this stuff glows 

Luminosity*

SPOTLITE glow film, series 4100 and 4400 CLL is neither electrically nor radioactively excited, and the intensity of its light radiance diminishes on a pattern of two phases on a curve chart.  In phase one, the glow factor will decay at an accelerated rate and within a half hour, approximately 80-85% of the brightness value is depleted.  However, the human eye is capable of undergoing  numerous changes in becoming sensitive to objects in darkness and the average person will become "dark adapted" at a rate that roughly matches the declining light curve.  Approximately eight hours is the period of time for phase two of the light curve which remains visible to persons completely "dark adapted".

In principle, this chemical light source is designed to absorb energy from any nearby ambient light source such as incandescent light, florescent lamps, and sunlight.  Once the source of extraneous light is shut off, SPOTLITE glow film immediately emits a light of its own that follows the description above.  There is no limit to the number of times the product can be recharged.  Three to ten seconds exposure to light is normally all that is required

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* thanks to protapes & specialties for this great info!