What is the Angel's share?
Armagnac must be matured in oak barrels. Oak barrels are permeable and they absorb a significant amount of liquid over time. As much as 5% of the volume of the new spirit we put into a cask will be quickly absorbed into the thirsty wood when it is initially filled – but it does not stop there.
As it ages, the brandy slowly evaporates through the wood of the barrels, modifying the alcohol content and concentrating the flavor. A smaller proportion, up to 2%, will go out through the atmosphere each year to be lost forever. This alcohol evaporation is poetically referred to as “the angels’ share” (“la part des anges”).
The loss in quantity is compensated by celestial quality. The red-tiled roof of the lofty stone barn in which these wines age is darkened by an alcoholic fungus that feeds on this ethereal repast. It is nearly as black as soot and exudes its own heady aroma of vanilla and honey.
Although 2% may sound like a small amount, for a small producer, as much as a season's worth of sales can evaporate through the oak barrels, through the roof of the chai and into the soft Gascon sky. At around 120 liters lost per barrel over a ten-year maturation period (multiplied by hundreds of barrels), it can add up to many thousands of liters (and surely some very tipsy angels!). The longer the armagnac sits in the barrel, the more is lost by the time bottling finally occurs. A 25 YEARS, for example, can lose up to 50% of its volume to evaporation!
A number of physical factors can influence the rate at which the angels help themselves. The skill of the cooper who made the cask will obviously have an effect. Also, oak is a natural substance that varies, and so there will be differences between casks, even if they were made at the same time by the same cooper from materials from the same source. The skill and attention of the warehouse man also come into play over the years.
Even these variables are by no means the end of the story. Temperature plays a part. Casks stored in humid conditions lose a greater proportion of alcohol than those stored at lower humidity levels. There are other factors as well, so the rate of loss is not consistent. It varies depending on the Angels thirst.