Column Still Design and Operation

I’ve recently been listening to some industry-related podcasts and have noticed that the word column or column still seems to be thrown around rather loosely. Without knowing any difference, one could almost assume based on the lack of context, that a column still is this uniformly designed distillation apparatus whose only goal is to is to strip the flavor out of the finished spirit that would otherwise be available if rendered from a classic pot still. That simply is not true. 

There are multiple column still configurations that range from continuous distillation stills to batch stills. Tall columns for neutral spirits production and short columns for more full-bodied flavor. Any system with no less than a single plate and utilizing forced reflux could be considered a column for batch distillation. On the continuous stills, it can be a bit more convoluted as a dedicated beer column does not necessarily have to utilize forced reflux to be considered a column. 

My point here is that when talking about the use of a column still to render a spirit, a bit more context should be used to help the listener understand how that column configuration has influenced the finished profile of the resulting distillate.

Why Use a Column Still at All?

The pot still is the oldest known distillation apparatus. And pot stilled spirits are some of the most sought-after spirits in the world. The pot still does its job well. Or does it? Well, there is no dispute that a pot still run by a competent operator does make a wonderful spirit. But the operator more or less has to exploit the inefficiencies associated with using a 2000-year-old technology. Plainly put, pot stills are not as efficient compared to a column at separating the constituents contained within the 100% infinitely miscible solution in the kettle.

To be clear (or clearly confusing) there are many ways in distilling to define efficiency. In the distillery, we can choose to exploit one or two efficiencies, but in doing so we often lose efficiency somewhere else on the efficiency spectrum. For example, the thing that saves labor hours very often requires more utility usage. Similarly, the thing that increases the ability to more efficiently separate the constituents in our distillation process very likely requires more utility. It’s just a matter of prioritizing the most desirable efficiencies against the fixed costs associated with running the distillery. Having said that, the column more easily separates constituents by exploiting a positive feedback loop supplied by the employment of forced reflux.

Does a Column Get a Bad Rap?

Distillers that use pot stills will often sight that columns are known for stripping out too many flavors in the finished spirit. The implication is that the resulting distillate rendered out of a column is a thin and lacking body. And those concerns do have merit. However, not all columns are equal. Utilizing a short column can absolutely increase efficiency with respect to proof gallon yield and the amount of time needed to get through a distillation run. By utilizing forced reflux, the column does a better job at more quickly compressing head constituents. The result being that the heads volume will be lower and therefore the heart’s volume will increase.

Two, three, and four plate columns can do a very nice job of rendering a very flavorful spirit while increasing efficiency. The short columns combined with aggressive reflux ratios can indeed render a full-bodied spirit. Adding just a few more plates into the lineup and reducing the reflux ratio can also render out a flavorful spirit while increasing the collection speed without compromising the ABV. In short, there are several ways to render out a flavorful spirit while increasing labor hour efficiencies.

The rub here is that accumulating enough knowledge and experience with column behavior usually requires capital. Once the capital investment has been made, the distiller is then handcuffed by the limitations of any particular still design. Basically, the distiller ends up making do with what they have to work with. 

A good analogy would be the golf swing in this instance. Who here plays golf? Does one modify one’s swing? Or does one choose the most appropriate golf club to execute the shot? As a distiller, are you able to manipulate the finished spirit through power or heat input management only? Do you have cooling management capability? Or do you render the expression based on the plate count? Pot stills by the way are only ever able to render out the finished product by virtue of power management. Columns (short and tall) have the luxury of utilizing power management as well as cooling management. In other words, the operator can manipulate the heat input as well as the flow rate supplied to the reflux condenser. Both of which provide the operator the ability to manipulate the flavor profile of the finished distillate.

Ok, let me backtrack a bit here. By no means am I saying that a column (short or tall) still makes a better spirit than a pot still. We have already confirmed that a pot stilled spirit is highly desirable. What I am saying is that a short column can increase yield and keep you close to a pot stilled spirit.

My recollection is that there are several distilleries making whiskey with a two-plate column. Those whiskies are delightful. Also, it is a known fact that highly regarded whiskey aficionados like Dave Pickerell (may he rest in peace) have recommended an 8-plate column still for whiskey production. Obviously, the operating technique is not the same for the short column as a taller column. My point here is that the column has two control parameters. Cooling management for the reflux condenser and power management for the kettle heat input. Any adjustment for either control mechanism in addition to plate count on the column has the ability to provide multiple flavor profiles for the finished distillate compared to the pot still that only has power management as its main control mechanism.

Am I poopooing the pot still? Absolutely not. Again, the pot stilled spirit is some of the most highly sought-after spirits on the planet. My point here is that column stills are not all the same and can be very diverse in their operating range based on the plate count. Additionally, column stills do not necessarily strip out too much flavor.

Data?

Please review this analysis table. This analysis was composed by Vinquiry Laboratories.

The baseline, fermented kettle charge for each example is identical. My understanding is that the heat-up time for each kettle charge is also identical. The first half of the panel clearly shows that a column can strip more constituents out of the resulting distillate. However, on the second half of the analysis, we can see that the column allows for more constituents to be carried over into the finished distillate.

	POT STILL	Two Plate Column	Six Plate Column	Sensory Notes
Distilled Beverage Panel	Completed	Completed	Completed
Acetaldehyde	8 mg/L	7 mg/L	4 mg/L	Strong fruity odor
Methanol	41 mg/L	41 mg/L	38 mg/L	Faintly sweet pungent odor
Ethyl Acetate	135 mg/L	116 mg/L	42 mg/L	Sweet fruity odor
Fusel Oils
n- Propanol	232 mg/L	227 mg/L	237 mg/L	Rubbing alcohol odor
Isobutanol	460 mg/L	473 mg/L	494 mg/L	Sweet odor
1-Butanol	<1 mg/L	<mg/L	<1 mg/L	Banana-like, harsh, alcoholic, and sweet odor
Isomyl Alcohol	940 mg/L	887 mg/L	1060 mg/L	Produces irritating vapor. Used as a flavoring agent in foods
Active Amyl Alcohol	252 mg/L	248 mg/L	290 mg/L	Black Truffle aroma. Disagreeable odor.

Often it is assumed that the taller column will strip more out of the distillate. But the table above clearly shows that the taller column allows far more fusels to be carried into the finished distillate.

Summary

1. Not all columns are equal.
2. Column behavior is often misunderstood.