So then I thought I should try this with my students. Without fire, of course. We set up my camera in my closet at school, so it would be plenty dark in there, and I gave them a couple of flash lights. We discussed contour lines, and I showed images of Picasso's light paintings. So far they are coming out extraordinarily cool. I can't post them since they mostly have kids in them, but here is one of mine:
Neat! I'm using a little LED flashlight. Laser pointers work, too, but you have to go very slowly drawing the lines, since red light travels more slowly, apparently. The best results I've gotten were with kids tracing each others' silhouettes, and adding interesting imaginary details. I've seen mermaids, fairies, angels, wizards, etc. My camera shutter speed is set on BULB, and I have a remote control shutter with a lock on it, so I can click it and it will hold itself down as long as I want it to. My F-stop is 25, the smallest it could be with my lens, and the film speed is 100. So in an almost completely dark room, I got no ambient light in the pictures at all.
There's my Deathly Hallows.
As long as you have a camera with adjustable shutter speed and a tripod, you can do this too!