Winegrowers Supplies  -  Egg shaped fermenters, polythene and ceramic

Fermentation or ageing in egg shaped vessels has been recorded since 6000 BC in Georgia, where they are buried in the ground to moderate temperature fluctuation.
In particular with ceramic containers, there is a small and gradual permeation of oxygen, less than that through an oak barrel but much more than through stainless steel.
They say that fermentation in the egg-shape is more spontaneous due to the ideal ratio without corners and edges. Wine, cider and beer can move more fluidly during fermentation and storage.

Speidel: made of food-grade polyethylene:

     
The smooth internal surfaces, without corners or edges, are easy to clean. Thet have a lid and two outlets:-