the currently prevailing theory holds that the heat of the ferment creates a torus vortex of convection currents (similar to the form of a mushroom cloud) within the egg. This moves the fermenting must or maturing wine around without intervention. Liquid near the surface of the container cools and gently sinks, unimpeded by corners. The liquid in the middle holds its temperature, but is gently pushed upwards. It then comes closer to the container surface, begins to cool and continues the process. The lack of corners in the container mean there are no “dead areas” and so homogeneity within the wine