Pot Stills, Column Stills and the Shape of Spirit

Two distilleries can use the same malt, water and yeast and still make completely different spirit. Much of the difference is in the shape, size and material of the stills.

Why copper?

Stills are made of copper because copper reacts with and removes sulphur compounds that would otherwise make the spirit taste rubbery or meaty. The more contact the vapour has with copper, the lighter and cleaner the spirit.

Pot stills

A pot still is distilled in batches. Its shape steers flavour:

• Tall necks make vapour climb further; heavier compounds condense and fall back (reflux), so the spirit is lighter and more delicate. Glenmorangie's stills are famously tall.
• Short, squat stills let heavier, oilier compounds through, giving a richer spirit. The Macallan prides itself on its small stills.
• The lyne arm — the pipe from the top of the still to the condenser — matters too: angled upward it increases reflux; angled down, less.
• Slow distillation increases copper contact and lightness.

Condensers and worm tubs

Most distilleries condense vapour in modern shell-and-tube condensers. A few keep traditional worm tubs: a long coiled copper pipe sitting in a tub of cold water. Worms give less copper contact, so the spirit is heavier and more sulphury when young, maturing into meaty, robust whisky. Talisker, Mortlach, Dalwhinnie and Cragganmore all use worms.

Column stills

In 1830 Aeneas Coffey patented an improved continuous still — the Coffey, patent or column still. Wash goes in near the top, steam comes up from the bottom, and spirit is drawn off continuously at high strength. It is efficient and produces a lighter spirit, which made cheap grain whisky possible and gave rise to blended Scotch. Grain whisky, most bourbon and most Canadian whisky are made in column stills.

American distillers usually pass the spirit from the column through a second pot-type still called a doubler or thumper to refine it.

Double and triple distillation

Most Scotch malt is distilled twice. Triple distillation — traditional in Ireland and at Auchentoshan in the Lowlands — gives a lighter, smoother spirit. Some distilleries run a partial third distillation, and a few (like Springbank's 2.5 distillation) have their own systems entirely.

Next: casks and maturation.