People who enjoy whiskey are known to have strong opinions about most things. They argue over the meaning of terroir in relation to whiskey, disapprove of chill-filtered bottles, and question whether age is a reliable indicator of quality. The debate over whether or not to add water to a glass of whiskey in order to open it up, as well as where that water should come from and how clean it should be, is one of several whiskey-related topics that have divided fans over the years. 

Also read: The Fascinating History Of Whiskey

Throughout several stages of manufacture, a whiskey is exposed to water before it is bottled and long before it reaches your glass. The importance of using high-quality water in the production of whiskey cannot be overstated, from steeping barley to start germination (a crucial step in the pre-fermentation process for many whiskeys made with malted barley) and mashing to fermentation and proofing. While most connoisseurs understand the relevance of a distillery's water source in the production process, they occasionally neglect and/or lack comprehension of the significance of the type and quantity of water used to dilute a whiskey during a tasting. 

It's the right time to explore what happens in the glass when water is added to whiskey, though, since a growing body of research contends that this practise allows consumers to perceive a whiskey's flavour profile and character on a more nuanced level. 

Whiskey is made up of molecules of alcohol, water, and other flavourings that are arranged in a specific way. However, as alcohol content increases and water is added, the composition of the compounds and molecules changes in relation to one another, changing the flavour profile. 

Depending on the flavouring elements that exist in a particular whiskey, the connection is always shifting. These are affected by a variety of elements, including the spirit's filtration process and barrel finishes. Certain scents, especially those that are drowned out by the alcohol at higher strengths, maybe more discernible to the nose as a result of a molecule-by-molecule change in solubility in water. In essence, as the strength of the spirit fluctuates, certain taste components in whiskey become insoluble when it is diluted. When tasting, soluble substances are less noticeable, but insoluble substances are flavours that are perceived by drinkers. 

The way ethanol molecules (or the amount of alcohol in whiskey) rebalance themselves with respect to other molecules and the water itself is usually the cause of these flavour changes. Since ethanol molecules have two poles—one that is hydrophilic and the other that is hydrophobic—ethanol builds up on the surface of a glass of whiskey at relatively low amounts. These molecules arrange themselves in their preferred direction near the surface, with the hydrophobic (i.e., water-repelling) side facing up and toward the atmosphere. The ethanol at the surface exceeds its capacity above a certain concentration and some of the molecules that cannot fit retreat into the liquid's depths where they become soluble and less detectable to the human palate. 

It is preferable to keep clear of water that is overly mineral-rich when considering how the type of water affects the flavour of whiskey. The amount of water added to a whiskey during a tasting should never be significant, but the whiskey's age can affect whether or not it benefits from dilution. Older whiskeys that have undergone lengthy maturation cycles require more delicate dilution, if any at all, in order to avoid enhancing undesirable woody flavours and to allow the highly aged whiskey to showcase its time-filled flavour nuances. The fundamental guideline for tasting whisky is to keep adding water until the alcohol burn subsides. Depending on their level of alcohol tolerance, each person will need a different amount. 

It is preferable to keep clear of water that is overly mineral-rich when considering how the type of water affects the flavour of whiskey. The amount of water added to a whiskey during a tasting should never be significant, but the whiskey's age can affect whether or not it benefits from dilution. Older whiskeys that have undergone lengthy maturation cycles require more delicate dilution, if any at all, in order to avoid enhancing undesirable woody flavours and to allow the highly aged whiskey to showcase its time-filled flavour nuances. The fundamental guideline for tasting whisky is to keep adding water until the alcohol burn subsides. Depending on the level of alcohol tolerance, each person will need a different amount.