This refers to the amount of whisky lost during the ageing process. In order for whisky to properly age, it has to breathe. Anytime you store a liquid in a non-airtight container, you will lose some to evaporation.

However, The Angel’s Share actually plays something of a necessary role in whisky maturation. This process of evaporation is how distilleries eliminate some of the unwanted ingredients of their whiskies. Distilleries rely on this evaporation process to eliminate some of the alcohol and allow the other ingredients to take a more prominent role within the whisky.