A column still operates on the basic principle of distillation, but does so in a very efficient manner. The name refers to the shape of the still, which is built in a long straight column. Although earlier column stills existed, the creation of the modern column still is ascribed to a man named Aeneas Coffey who was an Irish taxman in the early 1800s. Because of this, a column still is also sometimes called a Coffey still.
Aeneas Coffey worked as a tax man and had a lot of issues with illegal distilling, moonshiners and smugglers. Due to his line of work he became very well acquainted with the distilling world and the art of making alcohol. And although variations on column style distillation existed, it wasn’t until Aeneas Coffey perfected it that it became widely used. As a parttime inventor he was enamored with the idea and technology of distilling and he came up with a two column style of still that was going to be way more efficient than the pot still which was widely used in whisky distilling and basically in any other area of distilled spirits.
The way a column still operates is best described as a series of pots within a long column, being able to continuously distill because you can keep adding a fermented product in the bottom without interrupting the process.
Throughout the column are plates with little holes in them allowing liquid to flow down and hot alcoholic vapors to rise up.
A fermented wash is being fed into the column still at the top, which will run over hot plates and through the holes down to the bottom. Throughout this process, the wash is being heated and the chemical process of distillation is taking place. What this means is that while the liquid flows over hot plates, the alcohol boils before the water does and turns into a vapour. As the liquid flows down, the alcohol evaporates at every plate and rises up. A lot of the time when the vapors reach a plate above it, it hits the bottom, cools, turns back into a liquid and starts flowing down again and the process starts all over again. This is a form of reflux and redistillation. This process happens over and over and over again within the column, giving rise to the word ‘continuous distillation’ as this process can be kept going continuously.
The pure alcohol and lightest volatiles reach all the way to the top where it can be collected and start to cool off. It can go through another column for even further distillation or it can be collected. Modern column stills also have extractors at certain points within the column that allows distillers to take certain cuts of the alcoholic vapours at certain places during distillation. This allows them to be very precise with the level of alcohol they want to extract and which volatiles they do want to have in their final product.
With column distillation you can distill in a much more efficient manner and reach way higher alcoholic concentrations compared to pot stills which can only do distillation in separate sessions. Column stills can reach up to 98% abv whereas pot stills typically do not reach abvs higher than 60 or 70%.
This way of distillation changed Irish whisky distillation and allowed irish whisky to become lighter and easier to drink. Most notably, it allowed whisky distillers who adopted the Coffey still to produce whisky in much larger quantities a lot faster. But that’s for a separate post!
Column style distillation is used in the production of most spirits, most notably vodka, gin and Spanish style rums. Due to their quality of being able to produce lighter spirits faster, it’s a very popular choice for modern distillers. And although they look complicated, the principle behind it is no different than pot still distillation or any other form. If you want to know more about the creation of alcohol, check out our other posts!