I'm sure you guys are pulling out your favorite new Scotch terminology at cocktail parties, and using those distillation terms in every Saturday's crossword, but now that we've covered the basics, I wanted to focus in on a certain kind of distillation—the kind that takes place in the pot still.
What's a pot still? Why does it matter? Well, I'm glad you asked. Today we'll chat about this distillation equipment's origins, what it does, and how it's used.
History of Pot Distillation
Distillation, of course, is an old technology. The earliest known examples of distillation are from the first century A.D. in both Greece and China. Early distillers used simple equipment to distill liquids. One of the earliest, and simplest, was the retort, a spherical vessel (usually glass) with a long neck that points down and away from the main body of the retort. The liquid to be distilled was placed into the vessel so that it collected in the spherical main body, where the liquid was heated. Vapor traveled up into the neck and then, as it condensed, the distilled liquid flowed down into a collection vessel. Retorts still have some limited use in modern chemistry.
The retort evolved into the alembic still. Initially, the alembic was also made of glass, but eventually copper supplanted glass. Copper, after all, is more durable than glass, and it also heats more evenly. The alembic also had a spherical body, a long curved neck, and a collection vessel, but while the body and neck were one piece of glass in the retort, the alembic has two separate pieces. The alembic still's neck branches off a cap that sits atop the body of the still.
Alembic is an Arabic word, and early alembic stills were used to make perfumes. The French variant, alambic is used to describe the stills used to make Cognac, or alambic charentais.
Parts of a Pot Still
The modern pot still is based on the alembic, though with some improvements. Pot stills are generally used these days when a distiller wants to emphasize the flavor and texture of the spirit they're making. If you want something rich and a little creamy-feeling, you want a pot still. Single malt Scotch, Cognac, mezcal, and rhum agricole are pot-still distillates, as are some bourbons and ryes.
The process used today is simple to describe but hard to master:
All spirits-making starts with fermentation. The process of distillation doesn't produce alcohol; it merely concentrates it. To produce alcohol, you need to ferment a liquid. Since we're discussing pot stills, we'll assume the liquid is either a grain-based wash (for whiskey) or a fruit-based wine (for brandy).
The wash or wine is heated in the pot at the base of the still. Vapors containing alcohol and some of the water rise up to the head, a cap on the top of the pot that captures the rising steam; the steam is drawn off into a tube called a lyne arm. From the lyne arm, the vapors travel to a coil, or worm, immersed in a tub of cold water, called a condenser. The water chills and condenses the vapors back into liquid, in this case mostly of alcohol. The alcohol is removed through a spout attached to the end of the worm; from here, the alcohol usually flows directly to a second still for another distillation, but in some cases, it's taken from the still immediately and aged in barrels.
Some stills have a thumper or doubler positioned between the main body of the still and the condenser. Many bourbon makers use thumpers in the distillation process. The name thumper derives from the thumping sound such a still makes.
The thumper provides a second stage of distillation, which both speeds up distillation and produces a smoother spirit. The thumper is a second pot that's not directly heated. The thumper usually holds wash or tails from previous distillations. Vapor from the pot passes into the thumper, heating up the wash or tails inside it. As the vapor enters the thumper, heat transfers from the hot vapor to the cooler liquid. The liquid in the thumper cools the vapor, removing water from it. As the vapor cools, the liquid heats up; the alcohol in the thumper turns to new vapor and rises up through an opening at the top of the thumper and then enters a second lyne arm, and then finally travels to the condenser.
Have you ever watched a pot still in action? Got any favorite pot-distilled spirits?