It's dry January and I don't plan on a bottle review this month. So it's a good time to resume teaching, and learning, about what goes into whiskey and whiskey-making. It's been almost three years, somehow, and it's starting to astound me how long I've been blogging. We left off, on the American side of the business, after first examining Rye (201), the original American whiskey, and then the development of corn whiskey (202), aka Bourbon. Next we'll explore the column still, something used heavily by American distillers.
The traditional method of making whiskey, alcohol from distilled grains, is with a copper pot still (briefly mentioned in Whiskey 101). This has been the case for many hundreds of years, as a medieval continuation of the earlier Alembic, and they are still the primary method of distillation in places like Scotland and Ireland. While pot stills vary a bit they're all somewhat bulbous in shape and that's a quick and easy way to identify them. Without getting into too many details, a fermented liquid, using the grains mentioned above, akin to beer, is put into the bottom of this copper pot and heated. Alcohol, which has a boiling point less than water, rises to the top and through the rest of the system, where it cools and comes out the other end. In effect you're creating a liquid with a higher alcohol content than you started with by boiling it and capturing the alcohol vapors. With pot stills everything is done in batches, there is only so much that can fit in one, and this is limiting in terms of production capability. Using a pot still also requires multiple distillations (usually twice for Scotch, three times for Irish) in order to raise the ABV to desired levels.
In the early 19th century individuals looked to improve on the process. The big breakthrough was by Aeneas Coffey, an Irishman, who invented the still bearing his name in 1830. Using two columns it's made for continuous distillation, where the 'wash' (beer) can be added throughout the process. Not only could the still work without stopping (and cleaning after every batch), it could gain a much higher ABV in one go.
Let's take a look at how it works. Both columns are heated by steam. The wash, added continuously, is piped through the inside of one of the columns and gets heated up. It's then dropped into the other column, near the top, onto a series of plates with holes in them. The liquid keeps dropping, slowly, down through the column, plate to plate until the alcohol (or ethanol) evaporates upward, eventually through the top of the still where it's cooled and becomes a (much higher ABV) liquid again. Water and other unwanted bits can escape the still through the bottom. Admittedly at first I was a little confused looking for diagrams of this because many (most?) of the column stills I've seen in person (in KY) were a single stack. The simple answer here is the two columns, like from the original Coffey design and seen in the images below, can be combined into one, with the plates in the lower half. This seems to be how it's done much of the time now, but it still helps in understanding the process to show two columns doing two different actions.
Simply put, the column still is just far more efficient. With pot stills the alcohol in the liquid goes from <10% (the beer, 'wash') to ~20-25% (after the first distillation, the 'low wines') to ~60-70% (after the second distillation, the 'new make' distillate to be aged). This is as high as distilling twice through pot stills can achieve. With a column still the liquid goes from <10% to ~45-60%, much higher after a single distillation. It's then typically ran through another smaller still called a 'doubler,' something similar to a pot still actually, to raise the ABV again to ~70%. This process can reach a much higher alcohol percentage (as high as 90+% supposedly) but then regulations come into play. To be labeled as Bourbon spirit must be distilled at a maximum of 80% ABV, so distillers make sure to produce their new make (or 'white dog') to be below that. This is all in addition to the fact column stills, unlike pot stills, can essentially run non-stop.
Now, not all American distillers use columns. And not all distillers in places like Scotland and Ireland exclusively use pots, for example the base of many Scotch blends are 'grain whisky,' i.e. not 100% malt, and these are often made by columns. The general idea with American whiskey is frequently mass production and, some drawbacks aside, that's why distillers here use the column still. They can make a whole lot.
Hopefully you found all that interesting. Until next time.
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