What's the best way to charge them up?
UV and Stage Lighting is what these are designed for, although you will notice them glowing after being exposed to sunlight or indoor lighting too (as long as it has UV content). For the stage, these continually soak up lighting and then, for the moments the lights dim or go completely black, the labels will shine back at you just at that crucial moment!
How long do they glow for?
Although the manufacturer of the glow material I use state they will emit a glow for up to 14 hours, (which is true - I've actually woken up at 3am with my board next to me still faintly glowing - probably best not to ask why I sleep next to my board), for practical use, I find the 'afterglow' period to be visible for around 20 minutes and, in real life gigging use under good stage lighting, they remain bright enough for a few vital seconds at the times the stage goes dark. Although the glow weakens after the intense initial brightness, they continue to charge up and continue to provide a useful afterglow for the next time the lights go out. The stronger your stage lighting, the more they absorb and the better they'll glow when the stage dramatically goes dark - usually just about the time you're about to pull off a face-melting solo!!!
What are they made of? Can I eat them?
The material I use is the best stuff you can currently buy on the market. Let's be clear on one thing - not all glow materials are equal! You can buy cheaper material, but the amount of 'stuff' they contain that glows, together with some other important things that I won't reveal here, determines their ability to glow and the length of afterglow. There are two types of Glow-in-the-Dark (GITD) techonology in use today - one is Zinc Sulfide and the other, newer, form is Strontium Aluminate. The afterglow with Strontium Aluminate lasts about 10 times longer than Zinc Sulfide, is completely safe and non-toxic (I wouldn't eat them though), and can be charged thousands of times over their useful lifetime. I use the highest quality Strontium Aluminate material currently in production.
I am a vampire. Can I keep them constantly charging and glowing?
Well, good evening to you! And yes, I know of a few people that have rigged up a portable UV (Ultraviolet / black) light for their board that keeps the labels glowing. Very cool. Hang on, I think UV kills vampires...