How They Work
Continuing with our quest to make this as simple as possible, we’ll categorize stoves by the “box of rocks” principle, and say that once we’ve listed stoves by fuel type (we’re done with this, right?) we can lay backpacking stoves into two operational types: pressurized and not.
Pressurized stoves have pressure lurking somewhere inside them, just itching to get out and cause trouble. When the pressure tries to do this, some of the fuel in there with it comes along for the ride. Once the fuel gets out things get interesting. If you remembered to bring the matches.
Unpressurized stoves work the same way but without any pressure. No pressure, no rushing around, no whooshing sounds. Things just naturally and quietly take their course. Which can be OK if it’s time for your nap.
Pressurized Stoves
These guys work by one of three principles.
Some stoves, the liquid-fueled ones, have a pump. Clever idea. A pump. You work the pump and build up pressure inside the fuel tank of the stove. This is called “pumping”.
Then you open the valve and light the thing. This is called “lighting”. Fuel comes out, mixes with air, and burns, and keeps on burning. (Sorry to bore you brighter ones by repeating this, but not everyone is like you.)
Other stoves work by getting hot and warming up their fuel on their own. They make their own pressure. Hot fuel inside the stove vaporizes and builds up lots of pressure, and this keeps the stove running. The hot, vaporized, pressurized fuel keeps banging off the inside walls until it finds that one little hole with the exit sign over it (and it will, rest assured), and makes its escape there, through the burner. Then the flame catches it and burns it to a crisp. Ha-Ha-Ha-Ha! Gotcha!
A stove like this, usually a kerosene-burner, or some white gas stoves like my old Svea 123R, needs to be primed. You put some flammable stuff on the burner and light it. With my Svea, it was an eyedropper or two of white gas. Priming makes the burner hot, and vaporizes fuel when the stove is first lit. The fuel then burns, makes more heat, and so on, and the stove continuously heats itself as it runs.
The third type of pressurized stove does everything on its own. This stove uses canned gas (remember the butane/isobutane/propane stoves?). These fuels have really low boiling points, from -44 degrees F for propane up to 31 degrees F for butane. Because of that they don’t have much patience for hanging around in a can at normal temperatures. Straight butane can get sluggish in cool weather, but it’s usually mixed with some combination of isobutane and propane to even things out. So in other words, they help each other.
Unpressurized Stoves
Unpressurized stoves use either solid or liquid fuels. If you think about it a little, you can see why it would be kind of dumb to try pressurizing a solid fuel stove. About all you could do is to make a mess. Solid fuel is already kinda sorta pressurized. It’s concentrated. Trying to put some more squeeze on it wouldn’t help much unless you have a lot of residual aggression to get rid of. If so, you really ought to try hiking a few more miles each day before taking it out on your stove.
Liquid fuels are fair game. Liquid fuels in unpressurized stoves just burn all by themselves when lit. No unnatural stress is involved. This kind of stove is limited to using non-explosive fuels though. In other words, alcohol. This is important. Repeat until you have it memorized. (Note to persnickety readers: OK, alcohol AND oil and stuff. Oil burns and it’s not explosive but remember, we’re not going there, so back off a little, OK?)
Paradoxically, something like white gas can’t burn safely except under pressure. Because white gas is kept in a pressure-proof fuel reservoir. Because running it through a cleverly-designed valve mixes the fuel vapor with the precise amount of air to ensure clean and safe combustion. Because it’s been designed by engineers who know how to build this stuff.
Frightening footnote: Amateurs designed the canoe, but professionals designed the Titanic. Yikes! How about that one? Luckily for all of us, engineers who are hikers, climbers, arctic explorers and backpackers are especially bright, and to date not one of them has ever been held legally responsible for sinking any ships whatsoever, not even the occasional small one.
Throwing a match at an open container of white gas will result in an explosion. It may not seem like an explosion most of the time, but even if you don’t really notice it, the vapors just above the liquid part of the fuel ignite with a “whoof!” Sometimes a quiet little “whoof!” Sometimes a loud one.
If you throw a match at a bucket of gas and in turn get sprayed by burning gas it shouldn’t come as a surprise to you, though it always feels like one. If you happen to be standing there when the big WHOOF! comes along, or the big “BANG!”, it’s not going to be your best day ever. So don’t try it. Instead, check out the alcohol-burning stoves we’ll get to in a bit. They’re about as safe as it gets. Leave the explosive stuff to the professionals.
Exercises
- Annoy someone today. You’ve been good up to this point, and you probably need to let off some steam. You get extra points if you can annoy person A and blame it on person B, or vice versa.
- Take an engineer to lunch. Engineers don’t get out much and will really appreciate the gesture. Just to be safe, though, wear a fake nose and give a false name, address and phone number. Being nice is one thing, but you don’t want this person to start annoying you. Be realistic here, OK?
- Write a report about interesting explosions throughout history. Typing is OK, but tight, neat handwriting is better. Sign your name at the end. Then mail your report to the U.S. Department of Homeland Security, and be extra sure that you proudly include your return address. The folks at Homeland Security will be impressed, and they will want to come and talk to you. Keep some cookies and milk on hand.