Instant hand warmers are great--just shake 'em up, and you've got spontaneous warmth to thaw your hands during the cold winter months. But they're awfully expensive, and not because they're complicated to manufacture. In fact, you can make them yourself in a few very easy steps.
1. Fill a large ziplock bag one quarter of the way full with calcium chloride ice-melt pellets (available at most hardware stores).
2. Fill a smaller ziplock bag halfway with water, close tight, and place inside the first bag.
3. Squeeze the smaller bag until it breaks open, to create a heat-producing reaction between 20 minutes and an hour.
Originally posted by Justin DiPlacido on Instructables.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.