Every spirit — gin, vodka, whisky, rum, tequila — begins its life as a humble fermented liquid. Understanding the basics of distillation helps you appreciate what is in the glass and why different spirits taste the way they do.
Step 1 — Fermentation
Before anything can be distilled, sugars must be converted into alcohol. Yeast is added to a sugar-rich liquid — grain mash for whisky, molasses for rum, agave juice for tequila — and over several days the yeast consumes the sugar and produces alcohol and CO₂. The result is a liquid of around 5–15% ABV, similar to a strong beer or wine.
Step 2 — Distillation
Distillation separates alcohol from water by exploiting their different boiling points. Alcohol boils at 78°C while water boils at 100°C. By heating the fermented liquid, the alcohol vaporises first. These vapours travel up through the still and are collected and cooled, condensing back into a liquid with a much higher alcohol content.
There are two main types of still. A pot still is a traditional copper kettle that produces spirit in batches — it retains more flavour compounds and is used for malt whisky and cognac. A column still (also called a continuous or Coffey still) runs continuously and can produce a much purer, more neutral spirit — used for vodka, grain whisky and many rums.
The cuts — heads, hearts and tails
Not all of the distillate is desirable. The distiller divides the run into three parts. The heads come first — they contain harsh, volatile compounds including methanol and acetone and are discarded. The hearts are the good part — the clean, flavourful spirit the distiller wants to keep. The tails come last — heavier, oily compounds that can be redistilled or discarded. Making the right cuts is a skill that takes years to master.
Maturation
Many spirits — whisky, rum, cognac, tequila — are aged in oak barrels after distillation. During maturation the spirit interacts with the wood, taking on colour and flavour compounds such as vanilla, caramel and spice. A newly distilled whisky is clear and raw; years in a barrel transform it into something complex and mellow.
Gin — a special case
Gin begins as a neutral spirit — essentially vodka — and is then redistilled or infused with botanical ingredients. Juniper must be the dominant flavour by law, but distillers add dozens of other botanicals: coriander, angelica root, citrus peel, cardamom, orris root and many more. The combination and ratios are the distillery's closely guarded secret recipe.