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When It Comes to Great Whisky, The Size of Your Still Matters

Why the size and shape of a copper still is at the core of whisky distillation.

Reiner Harscher/laif/Redux

In our editorial series The Macallan Rare Cask Society—sponsored by The Macallan Rare Cask—we will be looking at the qualities and characteristics that define Scotch whisky. Click here for more of our Rare Cask Society.

There is a reason Speyside has become synonymous with Scotch whisky. To produce deliciously smooth drams of single malt, the region has refined the ancient art of distillation. For one Speyside distillery in particular, The Macallan, that process has come to be defined by some curiously small stills.

The distillation of any sumptuous single malt takes place in two stages and with two distinct stills, both of which are usually made out of copper. First up is the larger wash still, its capacity ranging from 25,000 to 30,000 liters. Taking advantage of the different boiling points of ethanol and water, a base of barley mixed with water and later yeast is heated up, yielding alcohol-heavy vapors. To create that all-important alcohol content, the fumes are circulated out of the still into condensers. These condensers cool the fumes to form a boozy concoction known as “low wine” that’s around 21 percent alcohol by volume. The low wine then goes through a second distillation phase in a smaller spirit still—but more on that in a moment.

Why stills made out of copper? The distinctive qualities of copper make it perfect for whisky stills—and thus for developing the full-bodied flavor of fine single malts. This is partly due to the metal’s malleable nature and ability to cope with wear—not to mention its exceptional capacity to conduct heat. But the copper performs another important function: working as a catalyst in the distillation process. In this way, it assists with the formation of “esters”: sweet, naturally forming chemical compounds which, when combined with water, react to create alcohol. What’s more, this process keeps impurities to a minimum, helping to give us the delectable aroma The Macallan is known for.

Anyway, back to that smaller spirit still: the low wine created by the wash still in the first stage of the distillation process is run into the spirit still for the second phase. It’s at this point that The Macallan adds a little bit of magic to the process. The Macallan’s “curiously small” copper stills are said to be the most diminutive of their kind in Speyside. They’re so famous they've been represented on a Scottish banknote. You can find fourteen of these copper creations, all initially containing 3,900 liters of liquid apiece, on The Macallan Estate.

What makes these stills so curiously small? Former production manager Alexander Tweedie says that the stills’ size makes them ideal for “retain[ing] the heavy, oily, robust flavor within the…spirit.” The stills have also been meticulously crafted, with their singular dimensions ensuring that the spirit has as much contact with the copper as possible. This is important in the concentration process, which takes place by means of an extraordinarily measured period of boiling. As Tweedie explains, “It’s a bit like cooking at a nice, slow speed, where you’re enhancing the flavors within...It’s exactly the same with the distillation process.”

To guarantee the outstanding quality that is the mark of The Macallan, only a small amount—the absolute best of the spirit—is then collected as “new make” spirit which is then casked and matured. This 16 percent, known as the “cut,” is colorless in nature, and it is “reaped” with a typical alcohol content of 69.8 percent. The Macallan “finest cut” is one of the most fastidiously selected in the Scotch whisky-making industry, and it’s a fundamental reason why The Macallan’s whiskies have their voluptuously deep, full-bodied taste.

So whether sipping The Macallan Rare Cask with a dash of water, or savoring its opulent notes of chocolate, fruit, and spice on its own, spare a thought for those curiously small copper stills. They're back in Speyside working hard to create the perfect flavor. You may just enjoy the rich, smooth fruit of their labor that little bit more.