The Alcohol Content of Scotch Whisky

1. How much is enough?

Scotch whisky is usually bottled at 40% or 43% abv. But you can also find 46%, 57% and all the numbers between, and sometimes even stronger stuff. Why these differences? What's the background?

The law states that whisky must have a minimum alcohol content of 40%. That's the bottom limit. Since alcohol taxes are relatively high in many countries, only selected, more precious bottles surpass this 40% - 43% limit.

Especially in the low-price range customers compare prices without paying attention to the alcohol content. However, for an 0.7 or 0.75 litre bottle with 43% you have to pay some ten cents of alcohol tax more than for one with 40%. That's a noticeable disadvantage on the market for sellers. That's why the standard bottlings are usually bottled at 40%.

In duty-free shops the alcohol content plays a minor role since there's no alcohol tax. Producers just have to pay a little more for the additional raw whisky. 43% have been established as the standard. For the majority of connoisseurs, 43% seem to offer the ideal taste experience. Many 1 litre bottles and older single malts are bottled at this strength. However, the abolition of duty-free in the European Union led to many 1 litre bottles also being bottled at 40%. This saves the taxes within the Union in the so-called travel value.

2. History

Before industrial measuring was introduced, determining the alcohol content was difficult. Buyers used a trick. They mixed whisky with gunpowder and ignited it. If the flame was bright, the whisky was "proof", i.e. the alcohol content was right.

If the flame was bluish and weak, it was "under proof". If the mixture exploded, it was "over proof". Later it was discovered that the proof point is around 57% abv.

The British adjusted their alcohol scale around this point (57% = 100 proof). 3% abv correspond to 5 proof. The Glenfarclas 105 therefore has 60% abv. Please don't confuse American proof with British proof. The American proof figure is always double the abv.: 100 proof = 50%. Bourbons are often bottled above this strength. It used to be the precondition for the quality label 'bottled in bond', which has survived in some bottlings until today.

3. Angel's Share

Scotch new make is almost always filled into casks at 63.5%. During maturation the alcohol content decreases by 0.5% to 1% per year. Since every cask is a natural product and each warehouse has a different microclimate, each cask ends up with a different alcohol content, which explains the different strengths of single cask bottlings. With regard to evaporation, sometimes figures of up to 2% per year are mentioned, but these higher figures describe the loss of liquid, which includes evaporating water.

4. Chillfiltration

The latest trend goes towards 46%, which was started by Ardbeg, taken up by Bruichladdich and is now seen more often. The independent bottlers Signatory Vintage and Gordon & MacPhail bottle more and more malts at 46%, too.

It takes a bit longer to explain the reason for these additional 3%. Matured whisky contains dissolved materials that cause cloudiness when the whisky is cooled or diluted with water. Many connoisseurs still drink their whisky on the rocks, and the cooling makes these materials flocculate. A milky haze appears, which mostly, but not always, clears again after some time and warming.

But also other solid flavour carriers can appear in a high-quality malt whisky during maturation. Sometimes it's small white lentils that are predominantly made of wax-like materials.

Rarely a slight black haze can be observed. This is a remainder of the charcoal that is produced by charring the casks. In sherry casks, over several years a fine, brown sediment that comes from the sherry is deposited. 

For fear of complaints many producers used to chill filter almost all whiskies before bottling. When cooled down to 4°C, the solid materials form small particles and can be extracted quite well with multi-layered paper and kieselguhr filters.

Around the turn of the millennium the trend to produce non chill filtered whiskies emerged. You can leave out one expensive processing step and at the same time advertise a natural product. But you need to take counter-measures against the clouding when the whisky is cooled, which can be achieved by increasing the alcohol content to 46%. That way the aromatic substances remain dissolved and the whisky stays clear even when cooled down significantly.

In the end the preferences of the connoisseurs or consumers determine the alcoholic strength of the whisky. Customers caring a lot for the price are more likely to buy whiskies bottled at 40%, with which they can save alcohol tax and VAT. On the other hand, connoisseurs caring for quality will go for more expensive whiskies with higher alcohol contents, which promise more authenticity since they're not chill filtered.

One group of connoisseurs hasn't been mentioned in this article yet: The gourmets who buy cask strength whiskies and dilute them according to their individual taste preferences. But that's the subject of another article.

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Signatory Vintage - 05. Jun. 1975 / Jul. 1993
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Signatory Vintage - The Un-Chillfiltered Collection - 20. Nov. 1992 / 10. Oct. 2013
Original bottling - Single Cask - May. 1996 / Jul. 2015
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Original bottling - 03. Feb. 1998 / 06. Feb. 2014
Original bottling - 19. Jan. 1998 / 06. Feb. 2014