Understanding how distillation works is the key to understanding almost every spirit on the shelf — whisky, gin, shochu, and countless others all start with the same basic process. By heating a liquid until it vaporizes and then cooling it back down, distillers concentrate alcohol and draw out distinctive flavors. This guide breaks down exactly how distillation works and the different types it takes — pot still and continuous — so every glass of spirit becomes that much more enjoyable to drink.
What Exactly Is Distillation ?
Distillation is the process of separating and concentrating different components of a mixture by evaporating it and then condensing it back into liquid. In simple terms: a liquid (or a liquid-containing substance) is heated. As it heats, it turns into vapor and rises; that vapor is then cooled, and the vapor condenses back into a concentrated liquid. This process can be used to increase purity, raise alcohol content, or separate substances with different properties.
Distillation has a long history, with its conceptual roots often traced back to ancient Greece, where early observations of vapor and condensation laid the groundwork for the technique. The knowledge was later refined and expanded during the Islamic Golden Age — the alembic still is widely credited to the Arab alchemist Jabir ibn Hayyan — before spreading into Europe through Al-Andalus, the Islamic-ruled region of medieval Spain.
Photo: Rambiki still — image via Wikipedia
Distillation is believed to have reached Japan during the Edo period, where it took the form of a ceramic still known as the rambiki. The name is thought to derive from the Dutch word for “alembic,” reflecting the technology’s arrival via Dutch traders. Rambiki stills were used to produce shochu, medicinal spirits, and distilled fragrances during this period.
Single (Pot) Distillation
Single distillation — pot still distillation — takes place in a large, onion-shaped copper vessel. Fermented wash (the liquid produced after fermentation) is loaded into the still and heated from below to generate vapor. That vapor rises through a narrow neck at the top of the still, travels into a condenser, and is cooled back into a concentrated liquid. It’s the same basic process as distillation in general — just carried out in purpose-built equipment.
As the name suggests, pot still distillation can’t run continuously; each batch has to be distilled, emptied, and reloaded. Because of this, a single pass typically caps out at around 20–25% ABV, which is why malt whisky, for example, is usually distilled two to three times to raise the alcohol content further. Distillers stick with this batch-by-batch method rather than switching to continuous distillation because it’s precisely what preserves a spirit’s individuality and depth of flavor. Pot stills can’t match the output or consistency of continuous stills, but distilleries accept that trade-off to protect the distinctive character and aroma that define their whisky.
Pot stills come in several shapes and styles, and each one serves a purpose. The vessels themselves are traditionally made of copper, since copper reacts with sulfur compounds produced during fermentation and removes the off-notes and harsh flavors they’d otherwise leave behind.
The shape of each part of the still — from the body to the neck to the arm leading to the condenser — also influences the character of the final spirit, determining whether it comes out lighter or heavier in style.
Line Arm
〚 Left ｜ Light spirit — line arm angled upward 〛 〚 Right ｜ Heavy spirit — line arm angled downward 〛
Vapor rises naturally as the wash is heated. When the line arm points upward, vapor flows through more freely, producing a lighter spirit. When it angles downward, heavier vapor passes through instead, resulting in a heavier, richer spirit.
Head (Neck)
〚 Left ｜ Heavy spirit — straight-necked head 〛 〚 Right ｜ Light spirit — ball-shaped head 〛
This is the section where vapor rising from the heated wash briefly gathers before continuing on. When the head (neck) has a rounded, bulb-like shape, vapor condenses and falls back into the pot, softening the alcohol and producing a lighter spirit. With a straight neck, alcohol-rich vapor passes through more easily, producing a heavier spirit.
Pot
〚 Left ｜ Light spirit — larger pot 〛 〚 Right ｜ Heavy spirit — smaller pot 〛
This is the vessel where the wash is heated. A larger pot gives vapor more room to reflux — condensing and falling back in before it escapes — producing a lighter spirit. A smaller pot sends vapor to the condenser more quickly, producing a heavier spirit.
Heating Methods
There are two main approaches to heating a pot still: direct-fire heating and indirect heating, where hot air (rather than flame) is applied to the pot. Direct-fire heating is harder to control and prone to scorching, but it produces a bolder, more aromatic spirit with a heavier character. Indirect heating, typically applying hot air at around 130°C (266°F), is easier to control and more consistent, producing a lighter spirit.
Spirits Typically Made Using Pot Distillation
- Gin (gin production often combines both pot and continuous distillation)
- Rum (some rum is made using continuous distillation)
- Tequila
- Whisky (malt whisky)
- Brandy (Cognac)
- Shochu (honkaku shochu made from barley, sweet potato, rice, and other bases)
- Awamori (Japan’s oldest distilled spirit)
Continuous Distillation
A continuous still — also known as a column still or patent still — produces a cleaner spirit and higher alcohol strength than a pot still. Because the process runs continuously in a single pass rather than in batches, it’s far more efficient and well-suited to large-scale production.
The still is built around two connected columns. Wash is fed in at the top of the first column, known as the analyzer (or wash column). Heated steam enters at the base of the analyzer and rises through it, carrying alcohol vapor upward. That alcohol-laden vapor travels to the top of the analyzer and passes into the second column, the rectifier, where it’s condensed and collected as a distilled spirit — a neutral spirit.
An easy way to picture it: it’s essentially a pot still’s distillation process happening over and over, continuously, inside a single piece of equipment.
The Birth of the Continuous Still
The continuous still was made commercially viable by Aeneas Coffey, who patented his design in 1830 and had it granted in 1831. Believed to have been born in France, Coffey worked as an excise officer in Ireland before eventually owning Dublin’s Dock Distillery, where he refined and patented his continuous still. The invention made it possible to mass-produce relatively inexpensive grain-based spirit.
At the time, Scotch whisky was dominated by malt whisky made purely from malted barley — a whisky with a bold, distinctive character that didn’t sit well with the vast London market. But the continuous still changed that, making it possible to produce grain whisky from corn and other grains. Blending malt whisky with this new grain whisky gave rise to blended whisky — a smoother, more universally approachable style that a much wider range of drinkers could enjoy.
Blending whiskies from different casks — even within the same distillery — was initially restricted, but that changed with the Spirits Act of 1860, which allowed whiskies to be blended together while still held in bond. This opened the door to blending spirits from different distilleries as well, and from there, inexpensive, mass-produced grain whisky quickly gained traction in the market. Today, continuous distillation is used by whisky producers around the world.
Spirits Typically Made Using Continuous Distillation
- Vodka (some vodka is pot-distilled)
- Rum (some rum is pot-distilled)
- Whisky (bourbon and grain whisky)
- Brandy (Armagnac)
- Shochu (korui, or “Class A” shochu)
- Neutral spirits
In Summary
Pot stills are called “utsuwa” (vessel) in Japanese rather than “machine,” reflecting the idea that they’re essentially large kettles rather than mechanical devices. Continuous stills, by contrast, are thought of as true machines, hence the different Japanese terminology used for each.
Pot distillation comes with real drawbacks — it’s harder to manage, less consistent, and unsuited to mass production — but its defining strength is that it preserves the raw ingredients’ aroma and flavor, letting a distillery’s individual character shine through and producing a genuinely deep, flavorful spirit.
Continuous distillation, on the other hand, strips away much of that individuality and flavor, but its strengths lie elsewhere: higher alcohol content, mass-production capability, a cleaner spirit, and greater consistency.
The arrival of the continuous still didn’t just expand the range of spirits and production methods available — it helped spirits spread and be produced across the globe, making it an invention whose impact reached well beyond the drinks industry itself.
And importantly, the rise of continuous distillation didn’t make pot stills obsolete — they’re still very much in use today, especially for malt whisky. Neither method is inherently superior to the other; distillers simply choose whichever suits the spirit they’re trying to make.
