Category: Tales of the Cocktail

At the Tales of the Cocktail convention this year, I moderated a panel with three distillers who run column stills; one 5-column rum still, one continuous bourbon still, and one pot-column hybrid. 

John Jeffrey is the Head Distiller for Death's Door Spirits. He makes vodka, rum, and white whiskey and will be releasing aged whiskey in the future. The below information is what I learned from John and on my visits to other distilleries. 

They run what I've been calling a pot-column hybrid still, though I'm sure there must be a better name for it. There is a pot on the bottom and then it is attached to one or several columns depending on how they configure it. 

Part of the reason I proposed the seminar for Tales is that I would see these types of stills (usually in start-up or small distilleries) and dismiss them as being column stills in another form; or working just like other column stills. 

However, these stills, unlike those for bourbon and rum/vodka, are not continuous stills but rather batch stills. You make a batch, then start over with a new batch; as opposed to the other stills that can run 24/7 without stopping. 

In some of these stills, solids and liquids (beer with grains, fermented fruit chunks, etc) are put into the pot on the bottom. The pot separates out the solids from the liquids, as well as separates out water from alcohol. The mostly-alcohol vapors then go up through the column for rectification. 

Stripping Column

At Death's Door, they don't put solids in the pot still though. They employ a separate 'stripping column', which is basically a bourbon column that separates the solids from the liquids as well as concentrates the alcohol a bit. (The column is mostly stainless steel, but as we talked about in the bourbon column post, the copper is important to have in the top of the column – you can see in the picture that the top of the stripping column is copper.)

Stripping column at Death's Door Spirits. Note copper at top of column.

Making Whiskey, Vodka, and Gin on One Still

This liquid alcohol then goes into the pot and is distilled. It is run through different columns depending on what product they're making. For whiskey, they don't run the alcohol over a ton of plates in several columns to remove all the flavor. However, they want to increase the amount of time the liquid spends in contact with copper in the column, so they run the vapor through one or more columns with no plates inside. 

Death's Door Spirits Stills

Jeffrey said that for aged whiskey, they wouldn't do this, as many of the congeners break down over time in the barrel. But as they make unaged white whiskey, they want to get rid of more of those congeners right from the start. 

For gin, they do not put botanicals into the pot still, but instead pack them into a different column (circled in pink below). The alcohol alone passes through the pot and column on top of it, then the refined vapors pass through the botanical column. 

Gin botanical column circled in pink. Stripping column circled in blue.

In order to make vodka, they want a high-proof, clean spirit. Thus they refine the alcohol through several of the columns with lots of plates in them – over 40 plates in all. The two columns on the right are used for their vodka.   

So that's what I think I know about this type of still. If you have any questions, let me know and I'll try to get them answered. 

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How Column Distillation Works: Bourbon Edition

How Column Distillation Works: Multi-Column Rum and Vodka Edition

A Visit to the Fernet-Branca Distillery in Buenos Aires, Argentina

At the Tales of the Cocktail convention this year, I moderated a panel with three distillers who run column stills; one 5-column rum still, one continuous bourbon still, and one pot-column hybrid. 

Kevin Curtis is the Distillery Operations Manager for Michter's Whiskey. This company is building a new distillery with a continuous column still. He filled me (and the audience) in on how bourbon stills work. The below post is a combination of information gleaned from distillery visits, books, and Kevin's information at Tales. 

The Purpose of a Bourbon Still

As opposed to some other types of stills, for bourbon the focus is not on getting a pure alcohol out of the still. By law, bourbon must not be distilled to above 80% alcohol by volume. The focus seems to be more on the continuous and stripping nature of the column still, as opposed to a discontinuous (batch) pot still.

Scotch Vs. Bourbon Distillation

More on that: If you know about single-malt scotch whisky, you'll note that it goes through a copper pot still. However, only liquids go into the still. Grains are fermented into beer, just like in bourbon, but in scotch the solids are separated from the liquid beer before going into the pot stills. In bourbon, the solids and liquids go into the still together (in practice; there is no law about this). In a pot still, one would have to be careful that the solids didn't burn against the still, making it even harder to clean than just scooping out the leftover solids. 

A bourbon column still thus performs two functions: It separates the solids from the liquids, and it separates the liquids into mostly-alcohol (to keep) and mostly-water (to recycle).

How Liquid and Steam Moves Inside a Column Still

 As you probably know, a column still is filled with perforated plates. The beer to be distilled is pumped in near the top of the column (but not at the very top), and steam is pumped up from the bottom of the column. While the plates are perforated, this lets the steam come up through the still, but the beer does not drip down through these holes. Rather, the beer runs across each plate to the other side, flows down to the next plate and flow across it to the other side. 

The steam coming up through the column vaporizes the alcohol from the beer (which then flows to the top of the column), while leaving the water and grain solids to keep dripping down to the bottom. (As in every still, it is tuned so that the alcohol that has a lower boiling temperature evaporates off, leaving the water with its higher boiling point behind.)

Artwork by Camper English

The Top Part of the Still

 As I mentioned, the beer initially doesn't enter the very top of the still but near the top. Above that point in the still, the steam is being rectified on those plates. It is up there where copper is crucial, and where you find "bubble caps" in stills. More on those:

Column stills can be built from stainless steel but there needs to be interaction with copper at some point. In other stills (as we'll see in a future post), the part of the still where beer is being separated and distilled is stainless, and where the steam is being rectified there is copper.

Bubble caps provide additional refinement of the spirit and increase contact with copper. Some other stills (I learned this at Absolut) are filled at the top with bits of shredded copper or copper pieces that look like jacks for similar reasons.

This also makes it easier to replace the copper at the top of the still or inside the top when needed, rather than the whole still column that can last for decades.  

The Doubler or Thumper in Bourbon Distillation

Most bourbon undergoes a second distillation in a continuous pot still called a doubler of a thumper. Sometimes it looks just like a regular pot still. In other distilleries, it looks just like a flat-topped metal container- you wouldn't know it's doing anything.

In a doubler, the vapor off the column still is condensed back into liquid and this is run through the pot still. In a thumper, the vapor itself goes into the still to be redistilled (and makes a thumping sound that I've never heard but I associate with the sound of radiator pipes clanging in East Coast apartment buildings). 

This second distillation is needed to raise the proof of the distilled spirit a little further, and this can be done in a pot still because there are no longer any solids to worry about. The waste product of the doubler/thumper is additional water.

The only other place I can recall seeing continuous pot stills was in Jamaica for Appleton rum. According to my tour guide at Jack Daniel's, they do not run a second distillation through a thumber/doubler at all.  (see comments for a dispute on this)

Update: I was given permission to post this bourbon still schematic. You'll see that the beer goes into the still at Plate 15, the new-make spirit is condensed and sent to the pot still (doubler), then recondensed before entering the High Wine Tank at the end. 

 Anyway, that's what I think I know about column distillation in bourbon. If you have any additional questions (or corrections!) please let me know. In future posts, we'll look at other types of column stills and see how they work. 

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A Visit to the Fernet-Branca Distillery in Buenos Aires, Argentina