still, hybrid is a pot still with a rectification column attached to it. See still, continuous, and still, pot. This style of still became very popular with European schnapps producers and later with American craft distillers because of its versatility and its ability to process in small batches. See eau-de-vie and schnapps. The rectification column allows the distiller to produce a spirit of a very high purity, such as vodka, but the still can also be configured to produce richer, lower-proof spirits. See vodka.
The action of distillation is the separation of liquids that have different boiling points. The rectification column works to create distinct separation between the vapors of these liquid compounds (chiefly ethanol and water), more than a basic pot still can create. The column’s temperature is hottest near the bottom and cooler at the top. This temperature gradient allows lower boiling point compounds to rise to the top (where they can be collected), while those with higher boiling points remain lower in the column.
The most common column design contains a series of copper plates, which allow vapor to pass upward and liquid to condense and reflux down. Though these plates have many styles, they most often contain several bubble caps—a device that allows vapor to rise freely while creating a slight hindrance to liquid refluxing down the column.
During batch distillation, most of the undesirable volatile compounds (such as aldehydes, esters, acetone, and methanol) rise to the top of the column and exit through the condenser before the ethanol, which distillers seek to collect. While ethanol is coming through the still, most of the heavier compounds (including propanol, fusel oils, water, butanol, and amyl alcohol) stay lower in the column. With more plates in the column, a greater degree of separation can be achieved and a purer ethanol distillate can be collected. It takes a large number of plates, or more than one pass through the still, to reach the concentration of ethanol legally required to make vodka.
Most hybrid stills allow a distiller to turn plates on or off to allow a greater or lesser degree of rectification. Some designs allow the column to be bypassed altogether, to create a pure pot-still spirit with more congeners, or flavor-producing compounds. This versatility is especially useful in making whisky because some of the compounds considered impurities in clear spirits are the precursors of desirable flavors in barrel-aged spirits. The versatility of the hybrid still allows distillers to create several different styles of spirits from the same still.
Dikty, Alan, and Bill Owens. “The Distilling Process.” In The Art of Distilling Whiskey and Other Spirits, 24–39. Beverly, MA: Quarry, 2009.
Murray, Douglas. “Grain Whiskey Distillation.” In Whisky: Technology, Production and Marketing, 2nd ed, ed. Inge Russell and Graham Stewart, 179–198. Oxford: Elsevier, 2014.
Owens, Bill. “Distillation Principles.” In Craft Whiskey Distilling, 12–23. Hayward, CA: White Mule, 2008.
By: Bill Owens and Andrew Faulkner