It’s a battle for the ages. On one side you have the anti-water contenders who claim that whisky should never be diluted with water or, gasp, ice. On the other side, you have the master distillers, blenders, and tasters who always add a few drops of water to their whisky. Guess which side is correct?
Actually, we don’t have to guess anymore. A Swedish chemist took the time to figure out if, how, and why adding water to whisky makes it taste and smell better. We now have a definitive answer to the ‘adding water to whisky debate.’ And lo-and-behold those master distillers and tasters were right all along.
Björn Karlsson — a chemist at Linnæus University in Sweden — created a computational model of the basic elements of whisky. The model included ethanol, water, and a compound called guaiacol — which comes from the charred casks and brings with it sweetness and smoky notes. Karlsson found that as water is added the ethanol both repels and attracts the water, sending the ethanol to the surface and bottom of the glass. As the ethanol heads to the surface the guaiacol attaches itself to those ethanol molecules. Thereby, the compound that imbues aroma and taste is propelled to the surface of the drink — or what Karlsson calls the ‘interface’ of the drink.
There’s more than just the moving of the smoky and sweet compounds to the surface. Karlsson explains that with the “ethanol molecules at the interface … that will then lead to a lowering of the surface tension.” So the water helps bring the flavor compounds to the surface and it makes the surface less rigid, allowing more flavor compounds to get out. So, there it is, add water to your whisky to help bring out the flavors. Yeah, science!
As long as we’re on the subject, how much water is the perfect balance for releasing the aroma and taste compounds without straight up diluting the whisky to a death? Karlsson doesn’t have that answer yet. “We have receptors on our tongue, in our nose, that are sensitive and depend upon the concentration of the specific components you want to detect,” Karlsson reports. “So if it’s too diluted there’s a risk that you actually don’t detect it with your nose or your tongue.”
It should be noted that for Karlsson’s experiment, he used a 45 percent cask strength Scotch whisky. Once the water was added, the whisky was diluted to 27 percent alcohol by volume, which is a fair amount of water added. And according to the paper in Scientific Reports, that specific dilution boosted the density of the guaiacol “by more than one-third.” Translation, water makes it better.