By Christopher Nyerges
[Nyerges is a longtime field guide, and author of 17 books, including “How to Survive Anywhere,” “Extreme Simplicity,” “Guide to Wild Foods and Useful Plants,” and others. He can be reached at Box 41834, Eagle Rock, CA 90041, or www.SchoolofSelf-Reliance.com.]
Did you all see the movie “The Gods Must Be Crazy”? A bush pilot drops a soda bottle out of the plane and falls into the midst of some aboriginal people. They have never seen such a device before and they all use it for a dozen or so practical uses. As far as they were concerned, the gods in heaven dropped them this new tool to make life easier.
An aluminum can is another of those multi-purpose objects that can literally be a life-safer if you’re lost or stranded. What good is an aluminum can, you say? With an aluminum can – and a bit of skill and your Swiss Army knife – you can make a fire, purify water, cook, signal, and do a few other things! That makes the discarded aluminum can a “multi-purpose tool.”
Let’s take a look at the many uses of an aluminum can that you happen to find.
MAKE A FIRE
I was a bit skeptical when I first heard about making a fire using the bottom of an aluminum beer or soda can, but it actually works. Well, it works if you prepare the can properly, and if you have a LOT of patience. The very bottom of an aluminum can is not a true parabolic dish, but when highly polished, it can be used to focus the sun’s rays to a point and ignite tinder.
Polishing the bottom
Because the surface of the bottom of the aluminum can is not polished, you need to give it a high polish in order for it to sufficiently focus the sun’s rays. When I first heard about this, people were suggesting that you should polish the bottom of the can with chocolate, a suggestion that I have never fully understood to this day. Maybe that suggestion was made because a hike is likely to have some chocolate in the back, but it is clearly not the best way to polish the can. The best polishing agent I’ve found for this is fine steel wool. However, it’s always good to know several ways to do each task, and if you don’t have steel wool, try tooth paste.
Polish the bottom of the can for about 10 minutes, until you have an obviously-bright and highly reflective surface. Once the bottom of the can has the high polish, you are ready to make fire.
Experimenter Eric Zammit of Altadena discovered by practice that he could quickly get a coal if he had polished the bottom of the can with the finest steel wool  for about 10 minutes. Then, using a small bit of rolled-up mugwort for tinder, he would have it smoking within 3 seconds, and he had a coal within 10 seconds.
Point the bottom of the can towards the sun, and then move your tinder into the bottom area, watching for the point where the light focusses to a point. When you find that point, keep your tinder there until you get your coal. This is akin to making a fire with a magnifying glass, except you are not focusing the light through the lens, but rather you are focusing the light back up to a single point.
One of the most important skills in the back-country is the ability to purify your water. If you’re just out for the day without all your normal equipment, you might not have a water filter or purification pills. So just fill the aluminum can with your suspect water, and boil it over a fire. Boiling will kill any of the biological contaminants that might make you sick.
If the water has stuff in it, then by all means pour the water through a cloth first.
COOK YOUR SOUP
You can also take the top off the can and use it as a small coffee pot or soup pot. Just punch two holes in the rim at the top so you can add a wire and suspend it over the fire.
Even if you don’t have your Swiss army knife for cutting the top off the can, aluminum is so soft that you could actually use a sharpened stick or stone for this job.
If for some reason, you can’t get a fire going, or if a fire would reveal your whereabouts, you can use that aluminum can for a makeshift water filter. You will punch little holes into the bottom of the can, and you will cut off the top of the can. A variety of filter materials have been tested, such as packing the can with clean socks.
In experiments that were done in Great Britain by Stefan Kallman in the 1980s, he found that he could create a reasonable water filter with an old aluminum can. He cut off the top of the can, punched holes in the bottom, and added sphagnum moss to the bottom. Then he filled the bulk of the can with a blend of charcoal, peat, and more sphagnum. He added a thin layer of small pebbles to the top. These were ingredients that would be available in the U.K, but not necessarily everywhere.
Other filters could be clean sand, mixed with a bit of charcoal, or the already-mentioned clean socks (or other fabric that can be packed into the can).
A filter like this cannot be expected to be 100% effective, but it can help to remove some contaminants from the water.
It’s easy to make an emergency signaling mirror from an aluminum can. Just cut a circle or a square from the can. Aluminum is soft and you can do this with the scissors on your Swiss army knife, or with any knife.
If you’ve ever used a regular signaling mirror, you know that it helps to have a little hole in the middle of the mirror to sight through. Cut a small hole in a rectangle of the aluminum through which you will attempt to observe your intended target. If the sun is in the ideal spot in the sky, and if the person flying overhead happens to be looking your
way, perhaps someone will notice your signal mirror and hopefully someone will respond appropriately. Who knows?
Your makeshift signaling mirror from the side of a beer can needn’t be round, but I would at least round off the edges of a rectangle so you’re not holding a piece of metal that might cut your hand.
LEAVING A NOTE
You’re lost with nothing, but there’s an aluminum can. You can cut a piece of the aluminum and write a note on it for other people to read. You don’t need a pencil — just find a thin stick to carve your letters into the aluminum. Then hang it in a prominent place for others to see whatever you need to communicate. The piece of aluminum will be shiny and will be more obvious than a paper note which might get blown away, or rained on. This is akin to the aluminum tags that gardeners use to mark their trees and other plants.
All photos by Christopher Nyerges unless otherwise indicated
AS-BEERCAN-01: An aluminum can full of suspect water is suspended from a tripod. PHOTO BY HELEN NYERGES
AS-BEERCAN-02: The can is held in place with a cord tied to the flip top.
AS-BEERCAN-03: Face the bottom of the can at the sun, and place tinder in the “hot spot.”
AS-BEERCAN-05: Using an awl (or nail), punch small holes in the bottom of the can.
AS-BEERCAN-06: Stuff the can with filter material. In this case, cotton fabric is used.
AS-BEERCAN-07: Slowly pour your suspect water through the “filter.”