My 15-year-old was bored yesterday and came up with this idea:
Draw on wood using the power of the sun.
Normally I'm not a fan of solar power: a couple years ago, a solar panel manufacturing company was considering building in my city. Our city council starting reading the research and crunching numbers, and eventually declined the move. Why? The council members discovered that when you add up everything it really takes to build and run a solar plant, it takes MORE energy to produce each panel that it will generate in its lifetime.
Anyway, back to this solar-powered art:
A magnifying glass, when held close to something with bright sunlight behind it, creates a concentrated beam of light, as most any inherently pyromaniac 12-year-old boy might tell you.
So he used that as his woodburning technique, holding the magnifying glass steady in one spot until a little wisp of smoke appeared, then moving it over a fraction of an inch. (See the light beam below?) He freehand drew it as he went, though you could sketch in pencil first (which is erasable!) and then burn over those lines.
Note: there are some safety considerations here, obviously. One of them is keeping an eye on your child if they try this. And I recommend doing this in a nice green grassy area that is not prone to catching fire. Another is protecting yourself from the sun. He wore a jacket with a hood, since he sat with his back to the sun for about 2 hours to make this. Too bad he didn't think to put on pants instead of shorts.
Voila! Wood burning with no specialty tools necessary except a cheap dollar-store plastic magnifying glass!