What you're about to see shouldn't be tried at home.
In this experiment, a small jet engine is actually being created inside of a jam jar. A small opening at the top of the jar continuously feeds the vacuum inside of the jar as the fuel burns away, and the busts of air give the flame a pulse.
The pulse is what you're seeing as the flame waxes and wanes in the jar, and it gives the flame that weird crackling noise you hear.
Of course, the jar can only handle the heat and pressure for so long before it breaks, which is why the jar eventually gave out.
Still, what you just witnessed was a miniature jet engine in a jar. And that's priceless!