I can’t claim credit for this video, but my friend Matt caught this on high-speed and I think it is pretty incredible.
The amazing thing is that the flame separates from the wick as the air cavity closes. The air flow out of the cavity is fairly fast as the neck pinches closed. Previously, researchers found that the air flow generated by the pinching off of the air cavity can create a jet of air that is moving faster than the speed of sound. What happens is that the closing neck of the air cavity acts as a nozzle. As the surrounding water pressure and surface tension of the bubble cause the bubble to collapse, air is forced out through the constricting nozzle. The air flow is strong enough to cause the flame to separate from the wick.