The “angel’s share” is the poetic term for the portion of whisky that evaporates from the cask during maturation. As whisky ages in oak barrels, a small amount escapes through the wood into the atmosphere each year. This natural process is essential to whisky’s development, but it also means that some of the spirit is lost forever, a gift, as distillers like to say, to the angels.
The Definition of the Angel’s Share
In Scotch whisky production, the angel’s share refers to evaporation loss during cask maturation. This occurs because oak is a porous material, allowing both water and alcohol molecules to pass through. Over time, the spirit interacts with oxygen entering through the cask, which helps mellow and mature the whisky, but also results in gradual volume reduction.
The term is romantic in origin, but the effect is measurable — and significant over long maturation periods.
Why the Angel’s Share Happens
Two main factors cause evaporation:
Alcohol Loss – Alcohol molecules evaporate through the cask at a faster or slower rate depending on climate and humidity.
Water Loss – Water also evaporates, changing the whisky’s ABV over time.
In Scotland’s relatively cool and humid climate, alcohol tends to evaporate slightly faster than water, meaning ABV can slowly decrease as the whisky ages. In warmer, drier climates (such as Kentucky for bourbon), water loss can be greater, causing ABV to rise.
The Rate of Loss
In Scotland, the angel’s share averages about 2% of the cask’s contents per year, though this can vary depending on warehouse conditions, cask size, and age. Over decades, these losses accumulate dramatically. A cask maturing for 30 years might lose half or more of its original volume.
Cask size also matters: smaller casks have a higher surface area-to-volume ratio, which can increase evaporation.
Impact on Maturation
While the angel’s share reduces volume, it also plays a vital role in maturation. Evaporation helps concentrate flavours in the remaining whisky and allows oxygen to interact with the spirit, softening harsh notes and integrating flavours from the oak.
However, too much evaporation, especially over extended maturation, can lead to whisky becoming overly woody or even dropping below the legal minimum of 40% ABV, rendering it unbottlable as Scotch.
Notable Examples
Many distilleries reference the angel’s share in marketing or visitor experiences:
Glenfiddich – Displays casks showing volume loss over decades.
Auchentoshan – Offers tours explaining how the angel’s share affects flavour development.
Kilchoman – As a small Islay distillery with smaller warehouses, experiences higher-than-average evaporation.
Global Comparisons
In Scotland – Average loss of 2% per year due to cool, damp conditions.
In Kentucky – Higher losses (up to 5% per year) due to hot summers.
In Taiwan – Even higher losses (8–12% per year) at Kavalan due to tropical heat.
Frequently Asked Questions
Does the angel’s share make whisky better?
In moderation, yes. Evaporation concentrates flavours and aids maturation, but too much can diminish quality.
Can the angel’s share be prevented?
Not without sealing casks in a way that would stop oxygen interaction, which would halt proper maturation.
Why is it called the angel’s share?
It’s a romantic expression suggesting that the lost whisky is taken by angels in exchange for the magic of maturation.
Conclusion
The angel’s share is an unavoidable part of whisky-making, representing both a loss and a gift. While it reduces the amount of whisky available from each cask, it is essential for developing depth, complexity, and character. Every bottle of well-aged whisky is a little rarer, and perhaps more precious, because of what was given to the angels.