As with all Whisky drinking matters, preference is a matter of the heart, nose and tongue. But perhaps one of our finest laws is that Whisky must have a minimum alcohol content of 40% ABV (alcohol by volume). Although some Whiskies bottled at higher than 40% are considered more precious, many drinkers favour the lower alcohol percentage for its more accessible palate.
You’re also likely to pay more tax on Whisky stronger than 40% ABV, which is worth noting before going completely wild.
In actual fact, after a Whisky has been distilled and aged, its ABV is usually much higher than 40 or 43%, meaning that most bottles on shop shelves have been watered down slightly.
After distillation, a Scotch Whisky can be anywhere between 60-75% ABV, with American Whiskey rocketing right into the 90% region.
Before being placed in casks, Scotch is usually diluted to around 63.5% ABV (68% for grain); welcome to the stage cask strength Whisky.
For aspiring mixologists, cask strength Whiskies include Aberlour’s 69.1%, Bruichladdich’s undiluted 70-72% and Port Charlotte’s bottling around the same ABV mark.
When diluting a Whisky, a distillery has to take into consideration the angel’s share of alcohol which has been lost to evaporation during the ageing process. This is usually between 0.5 and 1% every year, so with every year of ageing, a Whisky will lose a little of its alcohol.
Not to mention that if you dilute a Whisky, you get more from one cask. During WWI the maximum bottling strength was temporarily brought down to 37.2%.
Single malt Whisky bottling can have various ABVs, as they will often include various Whiskies from the same distillery. Each cask in each distillery has its own microclimate, so getting an across the board ABV into one bottle is easier said than done.
Whisky can often go cloudy due to dissolved materials in the nectar including solid flavour carriers, charred charcoal, sherry sediment and wax-like lentils. The cloudiness usually becomes evident when it is diluted or cooled, and by cooling the Whisky to 4 degrees centigrade, the perpetrating substances can easily be extracted using multi-layered paper. Clever stuff.
Lower proofs tend to showcase sugary qualities, but it’s worth remembering that the higher the proof of the alcohol, often the more sugar in the spirit. So if you like sugar, you’re onto a winner with Whisky in general.
Timing is everything with dilution. Prior to cask filling, dilution is likely to produce a sweeter, smouldering, clean-cut oaky spirit with a bitter twist. Dilution after bottling can reduce some of the sugar flavours and does have a bit of a risk of producing soapy off-notes; hence why Scotch on the rocks is generally deemed a terrible idea.