Copper stills are almost sacred to distilleries—and here’s why

The room where a distillery’s copper stills are lined up is always a breathtaking sight. Not only because most of the stills gleam with polished copper, but also due to their sheer size. Capacities range from around 4,000 liters at Edradour to a towering 50,000 liters at Glenfarclas. The still helps shape the spirit, so it’s crucial that it remains exactly the same, batch after batch. And distilleries go to remarkable lengths to ensure that.

Let’s start with why pot stills, as they’re commonly called, are made of copper. First, copper is relatively easy to work with, allowing skilled craftspeople to create virtually any desired shape. It’s also an excellent conductor of heat, enabling precise control over the distillation process.

Copper also has a cleansing effect during distillation. A chemical reaction takes place that removes unwanted sulfur compounds and certain vegetal notes from the distillate. In this way, the copper in the still has a direct influence on the character and overall quality of the whisky.

The shape of the still plays a key role as well. Many pot stills have the classic onion silhouette, but there are also pear-shaped stills, stills with constrictions, and designs featuring so-called boiling balls that encourage more or less reflux. The exact shape helps determine how alcohol vapors move through the still during distillation.

Over time, dents or irregularities can form in a still, and these can affect the way vapors swirl during distillation. Copper is also relatively soft and, through ongoing chemical reactions, gradually thins as it ages. Inevitably, every copper still reaches the end of its working life.

At that point, the manufacturer must replace the old still and build a new one that replicates it as closely as possible. This involves more than just matching dimensions and profile; folklore even says they account for distinctive quirks and imperfections in the old still. It’s a story often told on distillery tours: that a whisky’s unique flavor is shaped, in part, by those very dents and irregularities.

It’s doubtful that pot still makers such as Forsyths in Rothes, in the heart of the Scottish Speyside, deliberately add all sorts of dents to their brand-new stills. The tale does, however, perfectly illustrate just how committed distilleries are to preserving consistent conditions during distillation. And above all, it remains a wonderful story to share on a whisky distillery tour.