From whisky to Cognac, the concept of the angel’s share, how much liquid a cask loses to evaporation, is one that is unique to every distillery. Millie Milliken takes a closer look at this costly but vital part of the ageing process. 

It’s true: there are some alcoholic liquids that have nearly swung me in the direction of believing in divinity. And while none have quite got me willingly through the doors of a church on a Sunday (or any other day for that matter), there is one supernatural story that never fails to enchant me – that of the ‘angel’s share’.

A quick question on my sophisticated data collection software (Instagram stories) solicited many a fellow drinks lover telling me where they were the first time they learned about the term: “a trip to Lagavulin on Islay”; “Speyside at Chivas Regal getting the grand tour from the master, Ian Logan”; “Officially? At the Aber Falls distillery”.

Yet a quick poll of my non booze-dwelling friends found that nearly all of them had no idea what I was talking about. So, what is the angel’s share and why does it happen?

Duppy Share

It’s not just angels that love spirits

Give it wings

The angel’s share is the amount of liquid lost from a cask during the ageing process due to evaporation. As a spirit ages, water and alcohol evaporate through the wood’s pores, rising off the cask and are lost into the atmosphere. Or, should I say, to some rather lucky angels.

But it’s not just angels who appreciate ageing spirits. Anyone who has been inside an old distillery may have seen a black substance slick on the walls when they looked heavenwards. This is baudoinia compniacensis, a fungus that thrives on airborne alcohol and as such it is particularly happy in warehouses and distilleries housing spirits. And “in the Caribbean, spirits called ‘duppies’ swoop between the islands taking rum as they go,” said Jack Orr-Ewing, CEO of Caribbean rum brand, The Duppy Share.

Whoever it is enjoying the alcohol, Scotch whiskies on average lose 2% of a cask’s liquid per year. The duppies are even greedier, taking about 7% per year from Caribbean rums. Over time, this can amount to a shockingly high proportion of the distiller’s liquid. On average a VSOP Cognac will have lost over 10% over its life in cask, an XO will have lost 30% and after 50 years ageing, your now extremely expensive Cognac will have lost a staggering 70% of its original liquid (image in header is courtesy of Delamain Cognac).

The Nightcap

The higher up the stack you go, the hotter it gets, and the greater the angel’s share

Location, location, location

There are a multitude of factors that can affect how much the angels get. As well as the strength of the liquid when it enters the cask, climate and temperature are two important ones and depend on the distillery’s location. Casks stored in humid conditions will lose less water and more alcohol than those stored in non-humid ones.

When it comes to temperature, a barrel kept in cold conditions will age slower than one in the hot climes of somewhere like Kentucky. Indeed, some Kentucky whiskies can lose up to 10% of their liquid in the first year while in the Caribbean, rums can lose up to 7%. 

And then there’s the design of the warehouse which can affect ageing and the quality of the resulting liquid. “In Cognac you have a wide range of options,” says Clive Carpenter, general manager of Gérant Domaine Sazerac de Segonzac and creator for Seignette VS Cognac. “New-build warehouses are rather hot and dry because they are made of breezeblocks and are taller which means you’ll get a lot of water evaporation. That produces Cognacs which age faster but are harsher on the taste buds. Old-fashioned warehouses are made of stone, by the river on beaten earth, [so they’ve] got a very humid atmosphere. There you can lose a great deal of alcohol and not much water and if you overdo ageing in a damp warehouse, you get Cognacs that are over flabby.”

Then there’s how the barrels are stored in the warehouse. Airflow is important and in larger warehouses, casks can be stored on racks meaning more air can circulate around then and there is more evaporation. At The Glenlivet in Speyside, according to the website: “we have a traditional (dunnage) warehouse, with a gravel floor and only a small number of casks. This helps us to hold on to liquid as best we can.” In contrast, if the casks are stacked in a Kentucky warehouse, the temperature of the top of the warehouse will be far hotter than at the bottom.

The Glenlivet

Inside a traditional dunnage warehouse at Glenlivet

Cask matters

Cask size and wood type can also affect angel’s share. Brand new oak will absorb more liquid quicker than second-fill casks while smaller casks with more liquid-to-wood contact will encourage more evaporation too. At The Glenlivet, “casks that hold fewer than 50 litres can show really remarkable losses, which also leads to a faster maturation.”

And when we’re talking casks, we’re also talking ‘devil’s cut’. This is the liquid lost to the cask (and not evaporation) depending on how porous the wood is. Jim Beam has even created a Devil’s Cut expression using its 90 proof bourbon and blending it with the absorbed spirit extracted from the barrel.

Angel, duppy or devil, losing a percentage of your liquid is a price every distiller of aged spirits has to pay. If they do exist, sounds like the bar will be well stocked in both heaven and hell.