Last week, I gave you a list of ten great bargain bourbons, and although I won't quiz you on this material, I certainly hope you're doing your homework.
As you might remember, I said last week that "the bourbon industry has the resources and capacity to make massive quantities of corn juice, and the expertise to do it well." I didn't go into the technical reasons that make bourbon so easy to mass-produce, but I'll do that now.
Bourbon benefits from being produced primarily in column stills, which allow distillers to continuously produce spirits, without having to stop after each batch to clean the still. In theory, anyway, this means round-the-clock production of your favorite booze.
Bourbon isn't the only spirit produced in columns; others include most white rums, nearly all gins and vodkas, some brandies (including Armagnac), and the grain spirits used in blended Scotch.
All caught up? In today's column, I'm going to discuss the basics of column distillation.
A Brief Pot Still Primer
To understand how a column still works, we'll start with considering how a pot still works. With pot distillation, you put a batch of fermented liquid (the beer or wine that you're planning to distill) into a copper pot. You cap and seal the pot and heat it. As the liquid heats up, the alcohol in the liquid boils first (because alcohol boils at a lower temperature than water does) and turns to vapor. The alcohol vapors rise up into the head of the still; then they're drawn off into an arm and then to a coil. The coil is submerged in cool water, which condenses the alcohol back into liquid. The liquid alcohol runs out of the coil and into a collection vessel.
But the vapors that rise are never purely ethanol. If they were, every batch of whiskey or tequila or brandy would taste like Everclear. The vapors are a mix of alcohol and congeners and other compounds that provide flavor and aroma.
A pot still allows a distiller to make only one batch of spirits at a time, and so the still needs to be emptied out and cleaned up before the next batch can begin. Also, pot stills can only distill to a certain level of purity: usually between 60 and 80 percent alcohol by volume.
Patent, Coffey, Column...What?
Column stills arose in the 19th century, evolving from basic designs by French, Irish, and Scottish distillers. The goal of these distillers was to develop a more efficient system of distilling, one that would produce a higher quality product, in greater quantity, and in a shorter amount of time.
Among these early pioneers was a Scotsman named Robert Stein. He invented a means of continuous distillation that he then patented. In Stein's time, a pot-based distillery could produce 5,000 gallons of whisky per year, whereas his newfangled still could produce 150,000 gallons.
Stein's still was the first to be referred to as a patent still, and it changed the face of whisky-making. Up to this point, the only whisky in Scotland was malt whisky, made in small volumes, in small batches, in thousands of pot stills all over Scotland. Stein's invention allowed distillers to make whisky in greater scale, but it also allowed for a new product: grain whisky. The name's confusing; malt whisky is a grain whisky in that it's made from a grain (barley). But in distilling terms, grain whisky is simply a whisky made from grains other than malted barley, such as corn, wheat, or rye.
Pot-still whiskies were inconsistent from batch to batch, from farm to farm, from still to still. Merchants in Glasgow, Edinburgh, and London sold malt whiskies, but they wanted a consistent product, so they started blending malt whiskies with grain whiskies, to create the first blended Scotches, similar to today's Chivas Regal, Johnnie Walker, or Famous Grouse. The Scotches that took Scotch to the world were blended whiskies, and they were all the result of Robert Stein's invention, and Aeneas Coffey's.
Coffey was an Irishman, who, a few years after Stein, invented a continuous still of his own, known today as a Coffey still. (Coffey also patented his still, so it's also sometimes called a patent still.)
So these terms all basically mean the same thing: patent still, Coffey still, column still, and continuous still.
How Does a Column Still Work?
Roughly speaking, imagine a tall column filled with pot still upon pot still upon pot still. A column still has partitions, or perforated plates, that set up chambers within the still. The mash enters near the top of the still and immediately starts to sink. The mash, at this point, is still low in alcohol, like a beer or wine.
The still is constantly heated from the bottom. Usually this entails pumping steam in to the bottom of the still and letting it rise. The top of the column is the coolest part, so as the mash enters, it sinks toward the bottom. As the liquid interacts with the steam, the heat vaporizes the mash and forces the alcohol and other volatile molecules up the still. (Water and grain solids in the mash fall back to the bottom of the still.)
Each time the vapors hit a plate, they start to condense again, and as they condense, the heavier stuff (such as the cogeners) stays behind in the condensation. As the vapors rise from chamber to chamber, and from plate to plate, they shed more of the stuff that isn't ethanol and keep more of the stuff that is ethanol.
Column stills can distill proofs as high as the 190s, or 95% ABV. Bourbon, brandy, and other spirits, though, are not generally distilled to such high proofs. Bourbon by law, for example, can't be distilled above 160 proof.
The alcohol vapor is diverted out of the top of the still and into a condenser, where it condenses out into liquid again.
In some cases, the spirit is then redistilled at least once, sometimes in a pot still, sometimes in another column. Vodka and gin are then cut with water and bottled. Whiskies and brandies, obviously, go into barrels for aging.
The Role of Copper
Pot stills are made of copper. Column stills are sometimes made from copper, sometimes from stainless steel, or sometimes from a mix. Of you might find an all-stainless still with copper elements inside it. Copper strips most of the sulfur from a distillate. Sulfur arises naturally in the fermentation process. It lends a sour taste to spirits, so it's best to remove it.
Sulfur reacts with copper to form copper sulfate, which separates from the distillate, removing the sulfur aromas from the final product.