Revisitng the idea of candle stoves, would anyone happen to know the energy density of vaseline/petroleum jelly? Can't seem to find it online. And does it burn any cleaner than wax?
I ran a small test and a tiny amount of vaseline in a beer bottle top, with a small wad of cotton wool smeared with vaseline as both wick and firestarter, lit with a firesteel, burned for a long time and threw off a lot of heat. It didn't seem too sooty either, though there was just the one flame of course. It would seem to beat a candle stove in at least one respect: that of being extremely easy to light with just a firesteel.
With the area of the wad being fairly large in comparison to the size of the bottle top, you get quite a wide flame as well, comparatively speaking, though the height was fairly small - comparable to a normal candle rather than to an alcohol stove. In a normal tealight candle, the flame width is limited by the thin wick, which I would guess reduces the burn rate of the fuel and lengthens the time you wait for a brew.
I'd imagine (with the benefit of ignorance) there's some optimal size of flat, round wick (like part of a cotton make-up removal pad, say) that would increase the amount of vaseline being burned whilst balancing that against the need for the limited supply of air to give clean combustion of the fuel.