How to Boil Water (when you have to build your own stove)
Lately we’ve been reading about several different low-tech methods of cooking. They all look great on YouTube, but we wondered just how easy they are to build and use. We decided on the following test: We would build three very different low-tech cooking tools and try to use each to boil a quart of water.
The three designs we considered were:
- The Soda-Can Backpacking Stove
- The Four-Slump-Block Rocket Stove
- The Fun-Panel Solar Oven
The Soda Can Stove
There are several resources online describing how to build a small alcohol-burning stove from a soda can, so I’ll only outline the process. The first step is to cut the bottom half off the can.
We had the most difficulty making this cut, because we initially tried create it with scissors. We soon developed a better way to get a clean cut with a uniform height. First, stack up some rigid, rectangular materials to the height you want to make your cut (a block of wood is perfect, books are typically too mushy). Then, place a razor blade atop the pile.
Use one hand to hold the razor blade steady while you gently turn the can against the blade. Don’t use too much pressure! The idea is to turn the can around several (about four) times, making a reasonably solid score line in the metal. Once you’ve got your line, use the tip of the razor blade to gently poke into the line — you just want to get a hole started.
Repeat this process for the top of the can, and use a can opener to remove the top lid.
At this point, all you need to do is poke some holes in the top of the can; we think these help with air flow, but aren’t sure. We found either a drill bit or a steel needle worked well for this. We used the bit/needle inside a pin-vise, which is a great tool for small jobs like this. The final step is to cut a rectangle of metal
Admittedly, a quart of water is probably more than you would use when camping. This type of stove lights easily and can be extinguished very quickly. The fuel will evaporate harmlessly if you spill it (not true of petroleum based fuels) and is inexpensive. Our stove left a fair amount of soot on the bottom of the pan (this might be because our design is not very efficient). This was probably the hardest stove to construct.
The Rocket Stove:
This stove was the easiest to construct, but it took us a little time to figure out how to use it. The stove is built from 3 regular 8-shaped slump-blocks, and one H-block. In total it costs about $5 USD to build. The rocket stove is basically L-shaped, with the H-block forming the corner of the L.
Initially, we had a lot of difficulty getting this stove to light — not enough oxygen seemed to be reaching the fire. Looking around on the web, we realized we were missing an important part of the stove — a small metal shelf that sits within the stove (you can make one out of pretty much any bendable metal). Fuel is supposed to sit atop the shelf, while the bottom is kept empty so that air can be drawn into the chamber for the fire. Once we added our shelf, lighting the stove was a breeze. We started by loading the stove with sticks, then added some shredded paper to start the fire.
Of the three stoves we considered, this is one seemed to be the most powerful. It is a little smoky when you initially light it and will leave a black residue on the bottom of your pan. However, we had no trouble boiling a quart of water in 10-15 minutes, using very few sticks. The stove requires a certain amount of babysitting as you cook, because the fuel needs to be gently pushed into the stove as it burns. The stove can’t be “turned off” immediately, though you can cover the chimney and fuel door to reduce the fire to embers.
The Solar Oven:
The instructions for the Fun-Panel solar oven are really well organized. You start with two rectangles of cardboard, which you fold together to make the “wings” of the oven. Then, you glue foil to the wings, completing the oven.
The instructions for this stove suggest that you place your pot in an oven bag, to create a greenhouse effect — the bag insulates the pot while allowing it to build up heat from the sun. We found that without an oven bag, the warmest we could get our quart of water was 140F (after 3 hours in the sun). With a small oven bag, we were able to raise the temperature to 170F. Ultimately, we were unable to boil water with this oven (though that may not be an issue for cooking a food like rice over several hours).