HOW DISTILLATION WORKS
The process of making vodka starts out the same as any other alcohol: a mixture of starchy plant material, water and yeast, heated and left to ferment. But that’s where the similarities end. For most other drinks, the by-products of the fermentation process form part of the character. You can taste the grapes in wine, the hops in beer and the grain in whiskey. But with vodka the aim is to strip everything back and get as close to pure alcohol as possible. This happens in the distillery. A distillery takes advantage of the unique boiling points of different chemicals to separate one component of a liquid from another.
Water boils at 100 degrees Celsius, turning from a liquid into a gas. Ethanol – pure alcohol – boils at 78.37 degrees Celsius. When you heat fermented liquid, the alcohol boils first. This means that you can collect that ethanol vapour and leave the water behind. The trouble is, the fermentation process produces lots of other chemicals, and many of them have boiling points similar to alcohol. To remove them, distillers need to boil and condense the liquid over and over again. The easiest way to do this is in a column still. It’s hot at the bottom, cool at the top and filled with perforated metal plates. As the vapour rises, it goes through repeated cycles of cooling, condensing, heating and evaporating, leaving many impurities behind.
No matter how many times the vapour passes through the still, it never comes out as 100 per cent pure alcohol. The practical maximum is around 97.2 per cent, and most distillers stop at 96 per cent. The final step in the process is to filter the liquid through activated charcoal, and then there are still trace impurities left behind. They’re so distinctive that chemists can pinpoint the country different vodkas were brewed in – and even the brand – just by looking at the molecules.