It may seem counterintuitive, but diluting whisky makes it more flavorful, according to a study published in Scientific Reports. In fact, many whisky drinkers already understand this, even if they don't understand why. Chemists Bjorn Karlsson and Ran Friedman at Linnaeus University in Sweden wanted to understand, so they they used a computer model to look at how the main components in Scotch whisky — mainly water, ethanol and guaiacol (a compound that comes from oak casks) — interacted together.
It's amazing to me how finicky the molecules in the main components can be, yet, considering how microscopic they are, they can make a big difference in the taste of a whisky (or whiskey, as we spell it here in the United States). It has to do with how they attract or repel each other. Since the guaiacol is the main component when it comes to the smell and taste of whisky, depending on how much those guaiacol molecules interact with water molecules and ethanol molecules determines the intensity of aroma.
The first factor is the liquid-air interface, which is where the whisky and air meet at the top of the glass. The more guaiacol molecules present at the surface, the more aroma and flavor you will taste.
Guaiacol molecules are more attracted to ethanol than water, and ethanol tends to "escape down into the bulk of the liquid," the study found. Basically the guaiacol molecules hang at the bottom of the liquid with the ethanol. The study also found that diluting whisky with water from 45 percent alcohol to 27 percent alcohol "boosted the density of the guaiacol at the surface of a glass of whisky by more than one third." The addition of more water changes where the guaiacol molecules hang out in the glass, making them easier to smell.
But, hold on. Does something with more aroma suddenly have more flavor? Yes, it does. Our sense of taste happens mostly through the nose, not the tongue.
Up to 80 percent of what we taste happens because we've smelled our food or drink first. The vapors from what's put in the mouth reach the olfactory receptors in the nose, and that sends the message of flavor to the brain.
What's the practical application to all this? First of all, ordering whisky and water or whisky on the rocks isn't ordering "a weak drink," as some may think. There's no prize to be won for drinking whisky straight, or neat, as if a "real whisky drinker" must drink it full strength. In fact, if you're drinking for personal enjoyment rather than drinking to impress others, having a little water in your whisky will increase the intensity of flavor, therefore increasing enjoyment.
The other practical application is understanding that water benefits whisky, but not too much water. The study didn't find a perfect water-to-whisky ratio, but The Guardian says the industry standard is diluting to 20 percent. I suppose the only way to really know how much water works for you is to do personal taste tests — the most practical application of water and whisky there is.