Gray Matter: How to Start a Fire With Only Compressed Air
Piston Pyro A thick-walled acrylic tube with aluminum plunger (from $45; survivalschool.com) forms a demonstration fire piston, revealing a bit of cotton set alight by pressure alone. Mike Walker You've probably seen contestants on Survivor trying to make fire by rubbing sticks together or concentrating sunlight with their eyeglasses. But among preindustrial fire-starting methods, it's hard to beat the portable convenience of fire pistons, used in Southeast Asia since prehistoric times. Almost all gases heat up when compressed. The harder and the faster the compression, the hotter the gas gets, hot enough even to ignite cotton wool or other flammable materials. Diesel engines work the same way: They have no spark plugs; instead the fuel/air mixture is ignited by compression as the cylinder closes up. Perhaps most surprising is that this same principle also explains how many high explosives work. They are called "high" because their explosive reaction expands through a...