Why is a Copper Pot Still Still So Popular Among Rum Makers?

Retired Santa Teresa Pot Still with a "Thumper"and Condenser

     The alembic has three basic parts namely, the retort pot, the onion head and swan neck and, the condenser and coil.  The lower part of the still, which is the retort pot, is responsible for firing or heating. The pot resembles a cauldron with a flat bottom to stand still on a heating surface, normally an electric stove or a hot plate. This is where the fermented wash is boiled until alcohol is vaporized, ahead of other materials in the wash because of lower the boiling point relative to water and other components of the wash.  The vapor rises into the onion head.  As the wash is heated, the steam naturally rises and swirls around the onion head that sits atop of the pot. The vapors slowly pass through the swan neck pipe sometimes called the lyne arm.  This is the delivery tube that connects the still to the condenser.

 

Hybrid Stainless and Copper Pot Still at Hemingway Rum Co.

         Copper is the preferred material in the construction of a still to impart flavor into the distilled spirits.  Stainless steel and copper are excellent conductors of heat, dispersing the heat evenly across the entire surface of the metal and creating a more even distillation.  Where neither stainless steel nor copper will not put harmful chemicals into your final product, copper has the advantage over stainless in that rum out of a copper still simply tastes better.   In the process of distilling, the sulfur coming from the yeast binds itself to the copper, making hydrogen-sulfide which in turn, forms copper sulfate. The copper sulfate sticks to the inside of the still after distillation is completed.   After thoroughly cleaning of the copper still, the copper sulfate is washed down the drain, and not into your rum unlike other stills made from different metals.

Classic Pot Still With Huge Lyne Arms at DUSA

    The lyne arm angle, diameter and material all have an effect in the final distillate. The angle determines how heavy or light the flavor of the rum, while the diameter controls the amount of vapor that can swirl through the pipe.  The lyne arm is usually made of copper, which helps speed up the moving vapors.  It also helps to eliminate undesirable sulfides and other chemicals produced during fermentation while it helps improve the flavor.

     From the lyne arm, the vapors move to the worm or the coil that sits inside the condenser with a top and a bottom fitting. You simply put the water supply hose into the condenser near the bottom and use the top outlet to prevent overflow. The water-filled condenser cools the alcohol vapors and turns it back into liquid, which then drips off through the tail box of the condenser.

Modern Pot Still at St. Lucia Distillery

     This is the basics of a pot still, the oldest and most common type of still used by craft distillers, home distillers and even the old moonshiners.  There is a reason for this, the simplicity of it and the flavor that it leaves in the final product.  A lot of your favorite rums are at least in part still being made with pot stilled distillate.