A - like Angels' Share

What does the term Angels' Share mean?

The term "Angels' Share" comes from the English language and literally means "share of the angels".

What is Angels' Share?

Angels' Share is the loss of volume of liquid in a whiskey barrel that occurs through evaporation.

Can you smell the Angels' Share?

But yes! Because the unmistakable, aromatic and slightly alcoholic smell that you immediately perceive in the nose when you enter a warehouse is due to precisely that volatile portion that escaped from the aging barrels and is destined for the angels.

How can liquid escape from an intact wooden barrel in the first place?

Through the microscopic pores of the wood and the tiny spaces between the individual staves, liquid from the inside of a barrel can escape to the outside through evaporation. This happens regardless of how carefully a cooper has built the barrel and how closely the staves are lined up.

How can liquid evaporate in the barrel?

As soon as a barrel is filled with fresh distillate, i.e. the new make, the process of evaporation begins. Since the barrels are rarely filled to capacity, there is usually a small reservoir of air left between the liquid surface and the top of the horizontal or vertical barrel, which is called the headspace. Barrel staves provide an additional increase in headspace by absorbing fresh distillate like a sponge. In contrast to already pre-occupied barrels, the staves of fresh, unoccupied barrels even absorb up to two percent of the total spirit volume after the barrel has been filled. During evaporation, those ethanol and water molecules that have sufficient energy leave the maturing liquid and enter the headspace in gaseous form as vapor. These molecules then push their way out of the barrel into the open via the tiny wooden pores and spaces between the staves.

What substances evaporate from the barrel?

During evaporation, it is primarily the main components of New Make, i.e. water and the alcohol ethanol, that leave the barrel. But other chemical substances in the distillate, such as volatile fusel alcohols, aldehydes, esters and sulfur compounds, can also evaporate in the barrel and thus find their way out into the open.

How much fluid is lost through the Angels' Share?

In Scotland, these liquid losses occur at an annual rate of about two percent of volume on average. As a result, after eight years of aging, about 15 percent of the whiskey is lost through evaporation alone. After 20 years, the volume in the barrel may even have decreased by a third or more. For a completely filled 250-liter cask, that would still be more than 80 liters lost through the Angels' Share. A considerable economic loss! Since the evaporation rate depends, among other things, on the temperature, the annual evaporation in hotter climates, such as in India or Taiwan, even reaches a double-digit percentage and is accompanied by even higher volume losses.

What is the Angels' Share at St. Kilian?

Here in the Odenwald, it's definitely a bit warmer than in Scotland. That's why the Angels' Share is also somewhat higher. In the cooler warehouses in our Bunker City, the volume loss is between three and four percent per year on average, and in the warmer warehouse at the distillery in Rüdenau it's even slightly higher. This is in line with the order of magnitude granted to us by customs. This is because German customs allow a volume loss of up to four percent per barrel per year, tax-free. Anything above that has to be taxed by the distillery. This means that in this case we would have to pay for something that, in the end, is no longer there.

Which escapes faster from the barrel, water or ethanol?

Water and ethanol are the main components in New Make, which is usually filled into the barrel with an ethanol content of 63.5 percent. Both escape from the barrel at different rates. This is because their evaporation rate depends on the ambient conditions of the barrels in the warehouse, such as temperature and relative humidity. The physical reason for this is the tendency of similar systems to converge. Thus, the amount of water in the distillate inside the wooden barrel always tries to balance with the amount of water surrounding the barrel, i.e., the humidity in the warehouse. When the humidity in the warehouse is high, this atmosphere surrounding the barrel is already saturated with water, so the amount of water in the liquid that gets out of the barrel by evaporation is less than ethanol. Conversely, a less watery environment surrounding the barrel, i.e., drier air in the warehouse, provides a relatively greater evaporation of water from the barrel to compensate in this way for the greater moisture differences between the interior and exterior of the barrel.

Is the Angels' Share the same in small warehouses?

No. Even in a Dunnage Warehouse, where a maximum of three barrels are stacked on top of each other, there are different evaporation rates. Since ethanol is heavier than air, the alcohol will tend to stay at the bottom of the warehouse. As a result, proportionately more water than ethanol will evaporate from the bottom barrel in the row to compensate for the moisture differences. The top barrel, on the other hand, is surrounded by less ethanol. Thus, the ethanol-to-water ratio of the Angels' Share from this barrel will be different from that of the bottom row of barrels.

What is the consequence of the different evaporation rates of ethanol and water?

At a high humidity and lower temperature in the warehouse, therefore, relatively more ethanol than water evaporates from the cask and the ethanol content decreases as the whiskey matures. This is the typical situation in Scotland, where relative humidity is often 80 to 90 percent, especially in winter. In contrast, in relatively hot and dry climates, such as in the American state of Kentucky, more water than ethanol is lost through the Angels' Share, leading to an increase in the ethanol content in the cask as the whiskey matures.

So what conditions does the Angels' Share depend on?

The total amount and the relative rate at which the main components, water and ethanol, escape from the wooden barrel by evaporation depend on the following parameters:

• Type of wood from which the barrel is made
• Barrel size (the smaller the barrel, the larger the Angels' Share)
• Barrel type (fresh barrel, barrel preloaded once or several times)
• Quality of the barrel or craftsmanship of the cooper
• Type of ripening warehouse (Dunnage or Racked Warehouse)
• Temperature and humidity in the warehouse
• Alcohol content of the New Make (filling strength)
• Position of the barrel in the respective warehouse

Does the Angels' Share also have positive effects?

Of course! Because if something escapes from the barrel, then something else can flow back in. And that is air. An exchange with air is extremely important for maturation. This is because the oxygen contained in the air causes oxidation, which is a significant process in the maturation of whiskey in the barrel. Thus, the alcohol ethanol, as well as other alcohols, such as the fusel oils, can be oxidized with oxygen to form chemical compounds, such as aldehydes and acids. These aldehydes can further react with alcohols to form aroma-giving compounds. The acids, in turn, react with alcohols to form esters, which are noticeable in the aged whiskey through their extraordinarily fruity aromas.

Is it possible to see the Angels' Share?

Indirectly, yes. There is a black, soot-like fungus that feeds on the evaporated alcohol ethanol. Its Latin name is Baudoinia compniacensis. This fungus grows on the walls of warehouses and can even spread to surrounding trees, shrubs and buildings. Blackened warehouses indicate from a distance that whiskey barrels are stored inside. These externally discolored walls can be seen in the USA and Scotland as well as here in Bunker City.