During the maturing process of whisky, about 2% of the liquid evaporates from the barrel each year. Two percent doesn’t seem much, but the longer the whisky is maturing in the barrel, the more will be lost. For example, a 20-year old whisky can lose up to 40% of its contents due to evaporation.
The Scots call this phenomenon The Angel’s Share, the part of whisky that is reserved for the Angels.
But how is it possible that whisky in a closed barrel evaporates?
Despite the oak barrels, in which whisky is maturing, being well sealed, evaporation will take place because wood is naturally a porous product. The barrels absorb a considerable part of the whisky after a while: part of it ends up on the outside of the barrel, where it will evaporate.
What influences the evaporation?
There is a number of factors that influences the degree of evaporation. The size of the barrel is an important factor. Whisky that is maturing in smaller barrels tends to evaporate more, because there is more contact between the liquid and the wood. Also the quality of the wood plays an important role. European oak has a less dense structure than American oak, which makes it a less porous type of wood and American Oak is the most common wood for making the barrels.
Another factor that influences this process is the climate. At higher temperatures the liquid expands, whereby the wood of the barrel will absorb more of its contents and in effect evaporates more. You also have to take humidity into consideration: In Scotland, for example, the humidity is very high, so just a little of the water will evaporate eventually. If the humidity is much higher, in some parts of the USA for example, more water will evaporate.
The Devil’s Cut
Also the Devil plays a minor role here. At the Jim Beam Distillery in Kentucky, USA, they claim that they can extract the liquid that is being absorbed by barrel during the maturing process. They do this, by filling the emptied barrel with water, spin it round at very high speeds and then they blend this extracted liquid with a 6-year old Bourbon.
This product is being marketed as Jim Beam Devil’s Cut.
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