Thoughts on Alcohol by Volume (ABV)

What is the optimum strength at which to drink whisky?

The simple answer to this is that there is no optimum strength. Several factors should be born in mind, including personal preferences, the strength and character of the liquid, the circumstances of where you are tasting and when, but I always urge consumers never to be shy about adding water. The old misogynistic saying “whisky is the only other thing a Scotsman likes naked” is complete nonsense. High strength spirit will burn your nose and numb your taste-buds, while a drop of water almost always enhances flavour, although you have to be cautious when the whisky is heavily ‘sherried’. Blenders generally work at a reduced strength of around 20%ABV.

But this simple question set me thinking more broadly about ABV. Notwithstanding what I say above, bottling at high strength – so-called ‘natural strength’ or ‘cask strength’ – is highly desirable, since the alcohol inhibits the loss of certain volatile flavour-bearing compounds. If the strength is reduced on the bottling line, these volatiles will have blown off. Indeed, the reason reduction below 40% is prohibited is that, as the chemists say, the fall-off in flavour is ‘catastrophic’. Far better to reduce to your preferred drinking strength in the glass, then enjoy the benefit of enhanced aroma and taste.

Recently I was investigating a sample of Macallan 110 Proof 12 Years Old @ 55%ABV.

110 U.K. Imperial Proof equals 63%ABV, although the label states 55%ABV, which is the U.S. Proof at 110. The traditional strength at which casks are filled is 63.5% (111 Proof). Strength decreases during maturation, typically at between 0.3% - 0.5% per annum, so the ABV might be expected to fall to 59.5% - 56.3% over twelve years. So this cask much have been filled at a higher strength than 63.5%.

The strength of new make spirit straight from the still is between 68% and 71%ABV, termed ‘receiver strength’. Long ago it was discovered that the ideal strength at which to mature the spirit was 63.5% and accordingly a measured amount of ‘reduction water’ is added. Of course, it is perfectly legal to fill the casks at receiver strength – this has the advantage of reducing the number of casks required per batch, but scientists say “Higher strengths should be used judiciously, as they will increase the levels of wood lipids and ethanol-soluble lignins, both of which will adversely affect the final processing of the matured whisky” (Professor Paul S. Hughes, The Science and Commerce of Whisky, 2021).

The standard bottling strength of 40% (70 Proof) was introduced in 1917 as a wartime measure by the then prime minister, David Lloyd George, a rabid tee-totaller who famously told Parliament in 1915 that “Drink is doing more damage than all the German submarines put together” and proposed a ban the sale of alcoholic drinks for the duration of the war. This was narrowly averted, but he then established the Central Control Board (Liquor Traffic) with powers to restrict liquor consumption as it saw fit. Among its many measures, bottling strength was reduced initially to 42%ABV (73 Proof) in June 1916, further reduced to 40% in April 1917.

Neither the licensed trade nor the whisky industry was happy about this. A memorandum complained to the Control Board: “Compulsory dilution to a degree that would rob high-class brands of their distinctive characteristics and practically reduce all brands to a common level of mediocrity, would obviously be to the advantage of those whose aim is cheapness rather than quality”. Peter Mackie, the peppery owner of Lagavulin Distillery and the White Horse blend had earlier criticised Lloyd George, when he was Chancellor of the Exchequer:

“The whole framing of the Budget is that of a faddist and a crank, and not a statesman. But what can you expect of a Welsh country solicitor being placed, without any commercial training, as Chancellor of the Exchequer in a large country like this”.