This is like a holding tank or reservoir for the Charentais Alembic. This recipient with its peculiar onion shape is filled with wine and is preheated by the swan neck pipe which passes through it. The heat is generated by the vapours from the pot or boiler. The pre-heated wine is subsequently passed to the pot for distillation. This unit is considered a time saver and is the traditional still for making Cognac brandies.