One field of our ongoing research is illumination, specifically passive, and emergency light solutions.
How to Efficiently Charge GITD Materials
A black light shining on a glow surface for 30 seconds will cause that surface to be 10 times brighter than a flashlight on it for 6 hours. Under black light, most pigments will get to 80% of their charge within seconds, 90% over 30 seconds, 95% over about 2 minutes, 100% in about 10 minutes.
Light sources in order from most to least efficient
- Direct Sunlight
- Black Light Tube
- UV LEDs
- Fluorescent Bulbs / long tubes
- Compact Fluorescent or CFL-spiral tube, screw-in
- Incandescent / standard light bulb
- Blue/Purple LEDs
- White LEDs
The efficiency of light as a phosphorescent charging source is determined by its brightness and its spectrum. White light is comprised of equal amounts of all of the colors, such as red, green, and blue. White light bulbs typically also emit ultraviolet (UV) light, which is the "color" above purple in the spectrum, which humans cannot see. Each part of the spectrum affects GITD materials differently.
- Red light actually discharges the glow pigments.
- Green light is neutral.
- Blue light inefficiently charges the pigments.
- Ultraviolet light efficiently charges the pigments.
A standard incandescent light bulb emits similar amounts of the four colors above. The green does not affect the glow pigments. The red discharges and the blue charges in similar amounts, which results in a cancelation. The result is that only the ultraviolet is working to charge the phosphorescent pigments.
The ultraviolet spectrum is broken down into subcategories depending on wavelength:
450 - 400 nm Violet Visible Light 400 - 320 nm UVA Long Wave Black Light 320 - 280 nm UVB Medium Wave 280 - 100 nm Short Wave Germicidal
Ideally, for black lights, you would use 365 nm LEDs.
- Lower frequency light will more effectively excite the material.
- If the frequency is outside the absorption range for the material, then it won't work.