And now for something completely different. Here’s a homemade backpack stove powered by wax. It’s not just a big candle, which would be weak. This stove supercharges the hot wax vapor with air so it blasts almost like a regular stove.
The result is a strong, not terribly dirty, wind-
As far as I know, nobody’s ever made anything quite like this before. You can make one, too: just click over to the Construction page.
Wax?! What's the deal with that?
When When we think of burning wax, we think of a candle. Wax consists of long-
A candle, obviously, puts out little power, and its little yellow flame is vulnerable to wind. Blow on it, and it goes out. Sometimes it's smoky. Just making a candle big, say giving it a huge wick (which this wax stove has, by the way), does little to solve these problems.
In contrast, fuels made of the smallest molecules, like propane and butane, vaporize readily, at room temperature. They spray out of a stove automatically, and then they easily, vigorously mix with air to create a hot, efficient flame. Kerosene and Coleman fuel can also be made to automatically mix with air in a stove burner head once the stove is pumped or primed. By the way, the older nonpumped, purely primed stove designs work well too and are much beloved by many. The last couple decades have seen a great variety of simple alcohol stoves emerge. Many of these also develop a bit of pressure and jet out their burning fuel for a dynamic mixing with oxygen.
Thus, this stove achieves a vigorous mixing of air and vaporized fuel by providing a forced stream of air.
How wax rates as a fuel
Wax is a fuel that contains about 18,000 to 19,000 Btus of chemical energy per pound. That’s essentially the same as the energy density of kerosene, Coleman® fuel, butane, propane, and similar petroleum-
How about alcohol? Alcohol contains only about 12,000 Btus of energy per pound. Thus, alcohol contains only
What else is going on in this stove?
Air enters the stove body through a round port on the side. The air then swirls around the entire fuel chamber, thereby heating the air, and enters the fuel chamber through the many air holes at the top. The heated air supercharges the flame and forms a swirling vortex that is mixed further by being ejected upward through a screen-
The supercharger sits beside the primary stove unit. This side-
The windscreen obviously protects the flame from wind, and the air tubing prevent the flame (often huge) from reaching the supercharger.
The stove's advantages
The stove is cheap (but not easy) to make, is way more powerful than alcohol stoves and almost as powerful as traditional expensive commercial stoves, is heavier than many commercial stoves but not all, performs well in inclement weather (but then white-
Inexpensive to make. Like all do-
Solid fuel. You’ll especially like this stove if you’re married to the idea that solid fuel is better. Wax fuel needs nothing besides maybe a wrapper in the way of containment: no bulky containers to carry around and dispose of. Wax is nontoxic, inert, nonvolatile, and nonexplosive (obviously). Indeed, wax is commonly added to foods and used in making candy. Molten wax, if spilled, will cool quickly, flow only a short distance, be easily extinguished, and never explode. If you use beeswax rather than paraffin, you’ll be using a renewable resource: declare your independence from foreign oil and greenhouse-
Good performance in cold, windy weather. The stove does well in cold weather if adequately primed with an 80-
Stability. The stove is very stable, owing to its low height of 3 inches and its pot-
Difficult to make. Cutting, folding, and riveting the supercharger housing can be tricky. Hooking up the wiring requires (the barest of) electrical knowledge. Soldering the wiring requires special skill. Consider it a challenge. See the Construction page.
Moderately fast heating. The stove takes a few minutes to prime and get up to full power. That's largely because the wax first needs to undergo its phase change from solid to liquid. Then, according to tests under standardized conditions, the stove takes 8½ minutes to bring a quart of water to a boil. That boil time is roughly twice that of a typical commercial stove. That’s not bad, though, and it's good compared to boil times of 12 to 14 minutes using alcohol stoves. The wax stove will serve well for all but the largest meals or largest parties.
Burn hazard. All stoves present an obvious burn hazard. However, in addition, the wax stove produces a pool of hot, molten, burning wax that will cause a nasty burn if spilled on the skin. If tipped over during use, the stove can leave a pool of burning fuel on the ground that would need to be extinguished by kicking soil onto it. After use, the molten wax will take several minutes to cool to a relatively safe temperature. Alcohol stoves, however, pose a similar hazard, and butane/propane and white gas are used under pressure, thereby posing (slight) spray, flareup, and explosion hazards if used improperly.
Moderate controllability. The stove has essentially two "settings": high and low, achieved by using and not using the supercharger, respectively. In the low setting, the flame is inefficient and may impart more soot on one's pot or pan.
Soot. The stove leaves one's cookware sooty. Some of the soot can be removed by pressing one's pot into soil and turning it back and forth.
Criteria where it's a wash
Functional practicality. The wax stove is about as compact, easy to use, and sturdy as most commercial stoves. Its fan is designed to run for thousands of hours, and its electrical components are probably about as robust (or finicky, your choice) as the plumbing, O rings, seals, pistons, springs, spindles, and other delicate parts in commercial stoves.
Weight. The stove's total weight as a system makes for somewhat complex comparisons. The stove itself, at about 13 ounces (with some fuel, a battery, and 1¼ oz. of priming fluid), is about in the middle of the pack of commercial backpack stoves in terms of weight. The battery will power the stove for 5 hours (conventional alkaline) or 12 hours (lithium), and thus extra batteries are probably not needed. Even so, an extra battery would weigh only 1 ounce (lithium) to 1½ ounces (conventional alkaline). However ...
Thirst. Typical conventional commercial stoves bring a quart of water to a boil using about 0.5 oz. of fuel. The wax stove performs this task using about 0.6 to 0.7 oz. of fuel. This greater thirst, again, is due to the solid-
Cost of fuel. The stove’s fuel can be gathered from home candle drippings, trimmings, and leftovers and then molded into convenient fuel sticks (see Preparation). In such a case, your fuel is free. If you buy wax at say $5 per pound from the local hardware store, then running the wax stove costs about half as much as butane or propane or about 4 times as much as Coleman® fuel. Wax, if bought, therefore rates somewhere in the middle in terms of cost. Already accounted for in these figures are (1) the rate of fuel consumption (see Thirst, above) and (2) the minor cost of the wax stove’s battery power at about 25¢ per hour.
Another new wax-
Googling and browsing on YouTube around 2012 revealed this: A designer, Raymond Gatt, created a backpackable wax-
Obviously, Gatt's design benefits from the use of inert, relatively safe, solid fuel — wax, of course — rather than liquid fuels with their various issues (toxicity, explosion potential, etc.). It's also far superior to our DIY project wax stove in many ways:
Elegant and well made
Extremely light: only 4 ounces
An efficient flame, with a relatively high blue-
No electrical components and few moving parts
Most things in life involve compromises, however. The product requires 16 minutes to bring a pint of water to a boil. That time must be at least doubled to allow for bringing a quart or liter of water to a boil. Cited output is a mere 1,100 Btu/hour, which, if you track these things, is about a tenth that of practically any other stove. Also, the stove looks finicky in terms of cookware it will handle.
Still, I say “hurrah” for what appears to be a clever, lightweight, wax-
Execute this project and use any resulting product solely at your own risk.