by In the PourLast Updated: 09/08/2017
There are many, many different ways to design a still. But there is one fundamental difference in a still’s basic architecture. It has to do with how the evaporation from the heated kettle is handled. Pot Stills capture more from the steam, while Column Stills capture more pure ethanol alcohol.
A pot still (aka alembic) is a traditional design used for many hundreds of years. They have a simple design that is easy to make. Even with advancements in engineering, this design is still in common use today.
Typically pot stills are fashioned from copper. Many centuries ago, it was a very common material and easy to work with. Copper also has chemical properties which makes it well-suited for a distiller. Not only does copper conduct heat well, but it also extracts undesirable sulphur compute from the distillate.
The classic pot still design is pictured above. The components have distinctive names based on their shape. The base part is called the kettle and is where the fermented wash is heated. As the wash evaporates, the steam travels through the onion top to the swan neck, and finally to the worm, which is a copper tube spiraling through the still’s condenser.
A column still (aka Coffey still, or continuous still) is a more modern design which arose from advancements in engineering. It is specifically designed to capture more pure alcohol and to exclude impurities. Column stills were invented in the 19th century and are commonly used by bulk and industrial alcohol producers.
Column stills are usually stainless steel, but may contain copper strips within them to extract sulphates. Their distinctive feature is a tall column attached to the top of the boiling kettle. The height of the column is specially calculated using the physics of vapor. At the top of the column is a pipe which leads to the condenser.
The vapor from the kettle contains alcohol, water, and some impurities. Alcohol has the lowest boiling point, which makes it more volatile and it rises quickly. As the other compounds in the vapor rise through the column, they cool down enough to condense and “rain” back into the boiling kettle. The pure alcohol is able to proceed to the top, where it is separated from the still and collected.
Difference in Taste
Why does the still design affect taste? Congeners.
When alcohol is fermented, the yeast produce certain byproducts called congeners. Some of these byproducts are desirable and some are not. Distillation from a pot still results in many more congeners than from a column still. Column stills are designed to produce a more pure distillate and therefore exclude many congners.
Certain types of liquor depend on congeners for flavoring, while other types try to minimize them. Congeners can be especially desirable when aging spirits; some complex aging reactions depend on them. Neutral tasting spirits generally attempt to restrict the amount of congeners in the product since they can have an effect on taste.
Generally white, neutral spirits are distilled in column stills and aged spirits are from pot stills. However, many producers use the “other” kind of still for various reasons.
|Pot Stills||Column Stills|
|Aged Rum||White Rum|
Distilling is as much an art as a science. Perfecting the blend of congeners in a product can be the difference between excellence and mediocrity. More artisanal or crafted spirits will tend to be made with pot stills. Conversely, it is much more cost efficient to use a column still to mass-produce a consistent and adequate product.