While the eau-de-vie matures in oak casks, some of it evaporates. This natural phenomenon is commonly known as ‘the angels’ share’ and amounts to the equivalent of some 20 million bottles a year. The angels’ share is a well-known expression found in numerous books on alcohol and its history, particularly those about cognac, of course. We do not know when the expression was first used, but its poetic aspect has certainly contributed to its widespread adoption.

Torula compniacensis
This is the name of the fungus caused by the angels’ share. As the eaux-de-vie mature in the cellars of the Charente region, some of the evaporated alcohol escapes from the oak casks. This natural evaporation aids the development of a microscopic fungus called torula compniacensis, which feeds on the resulting mixture of alcohol fumes and humidity.

A visible and costly phenomenon
The evaporated alcohol itself is invisible, but the fungus is easy to spot all over Cognac. Its presence is betrayed by a blackening of the walls of any buildings near the cellars. Every year, cognac-producers reckon to lose some 3 to 4% of the maturing eaux-de-vie into the atmosphere. In other words, the equivalent of around 20 million bottles stolen by the angels...