Troubleshooting Your Alcohol Stove
There might be a couple of reasons for this. First, the jet holes might be too small. It's difficult to enlarge holes in an existing stove, but go ahead and give it a try. But gentle, though—you could easily damage the stove if you aren't careful!
The opposite might also be true—the burner holes could be too large. Image there was no cover at all where the burner holes are located—it would burn whatever vaporized denatured alcohol happened to evaporate from the side walls, but you won't get any real pressure pushing the vaporized denatured alcohol upwards and outwards. If burner holes are too large, they might ignite, but even if they do, they won't burn well.
Another possibility is that there's a large gap between the top of the inner wall and the top portion of your stove. If the gap is too large, the building air pressure that should push the vaporized denatured alcohol through the jets might push it through the gap at the top of the inner wall. So mind your gaps! One reader suggestion blocked the small gap with epoxy and got his stove to burn for 35 minutes—far better than my stoves have ever done. So that might fix the problem.
One person reported this as a problem. He did state that the notches at the bottom of the inner wall were quite a bit larger than the ones I had on my stove and wondered if that might have been the reason. I can only guess, but it's a reasonable thought. The jets light when pressure inside the wall builds up enough to eject vaporized denatured alcohol out the holes. If the notches in the inner wall are too tall, however, and air can escape through them, over the surface level of the denatured alcohol and the pressure might not build up enough to push the gas through the holes.
He also worried that maybe the jets went out because the holes were too small. That probably would not be the cause, however, because if the holes were too small, they usually don't light in the first place. Once they're lit, they tend to stay lit until it runs out of fuel or air pressure—and holes that are too small wouldn't lead to either of those problems.
I never heard back of the guy with this problem, so I don't know if a new stove with smaller notches fixed the problem. But it's as good as theory as any!