Why copper is used to make whisky stills?
First of all, it is important to understand what distillation is. Distillation is the process of turning beer into whiskey. At the end of fermentation, the mash becomes a liquid consisting of 9% (ABV) alcohol and 91% water. However, after distillation, the alcohol content rises to up to 60% (ABV) or more. Because the alcohol has a lower boiling point than water (alcohol boils at about 78.5 degrees Celsius, while water boils at 100 degrees Celsius). Therefore the alcohol in the still will be converted to steam earlier than water. The process of distillation will separate most of the water from the alcohol.
Such "magic" happens in distillers made of copper. At this stage, the distillers need to feel which flavors are left in their creations and eliminate the rest, and copper is their faithful helper.
Copper has many features and functions, and its role in distillation is the most significant. As the alcohol vapor rises along the inner walls of the still, the copper holds the heavier elements firmly in place.This means that the longer the vapors are in contact with the copper, the lighter the final spirit will be. Thus, a taller still will bring a lighter character to the spirit than a smaller one. The size and shape of the stills can have a crucial impact on the flavor of the whisky.