How bright are the new Foursevens glow-in-the-dark T-shirts? Let's just say you could light a dark alley with one (we did). You could also toss one on as you leave the tent to go take a pee and feel pretty damn confident you aren't going to stumble into a poison ivy patch.
True story: I went through 5 different companies searching for the perfect shirt before settling on the same T-shirt company that NASA uses for their glow-in-the-dark needs. (And NASA thanks all you tax payers for them).
For maximum charge I suggest hitting it with a UV light like I do in the video above.