It’s a neat experiment, but not necessarily a handy trick for starting a fire should you find yourself without a match. Water has a high heat capacity, and is quite effective at absorbing heat energy from its surroundings with only minimal increases in its own temperature. To create steam that’s hot enough to start a fire, you’ll need an even hotter flame to superheat it—like from a blowtorch. And if you already have access to a blow torch, you might as well just skip the steam experiment altogether and start your fire that way.