Chapter 7
Twisted Shop Class » Hillbilly Hot-Tubbing

uicklime plus water equals heat, so I built a hot tub with 500 pounds of it. Self-heating soup sounds like something from the future: Push a button on the can, and three minutes later the contents are piping hot. But it's widely available today, along with selfheating coffee and hot chocolate. In Japan, I even found self-heating sake. Pretty high-tech. Or not. In fact, these products use a chemical reaction known since at least 4000 B.C.-the mixing of quicklime and water.

When you roast limestone at about 1,650°F, it converts to quicklime, a powder used to disinfect corpses in war zones. Mix quicklime with water, and it grabs and binds the water molecules, releasing lots of energy in the form of heat.