Large egg-shaped concrete vessels used to ferment white wine. There are distinct advantages to using concrete eggs instead of oak barrels or stainless steel tanks. The oval shape of the egg helps create a vortex causing the wine to roll in circular arcs, assuring a thorough active fermentation. The concrete itself holds heat well, so the warmth created by fermentation is not quickly dissipated, and the wine doesn’t experience wide temperature swings. Lastly, concrete is porous like wood, which allows for the gentle introduction of air, which softens the wine.