Pot still were one of the earliest still types used to separate ethanol from fermented mash (wash or wort). It is the modern descendant of the alembic still. Pot still are simple and somewhat inefficient for separating alcohol from wort. This is both good and bad. If you are trying to make a neutral spirit with no flavor and yield the highest alcohol content possible then a pot still is not the correct tool. Instead a reflux still may be the better option. If you are looking to produce an end product that is lower in alcohol, ~80% or less, and retain the flavors of the original fermented mash a pot still is perfect. This is the main difference between beverages like vodka and whiskey. Vodka has little to no flavor whereas whiskey has much more flavor and complexity. In addition to the way the wort is distilled, each mash recipe will have its own characteristics when distilled. This is one of many parts of the process where a whiskey maker can distinguish their product from others. Bourbon whiskey for example is made from a minimum of 51% corn whereas American rye whiskey is made from at least 51% percent rye. Each of these grains will expose their particular quality in the end product.
Anatomy of a Pot Still
The pot still has four main parts: The pot, neck (swan neck), lyne arm and condenser. The shape of the pot, angle of the lyne arm, condenser length, etc. will affect the flavor of the final product. This is another area where the brewer has the ability to create a distinct style of their own.
Pot: The shape of the pot is generally a cylinder that is wider at the top than the bottom. The pot is filled with the fermented mash and heated with fire or an internal heating mechanism. Most commercial distilleries heat the wort (aka wash) with 400 degree steam pumped through tubing that is coiled inside of the pot.
Swan Neck: The neck allows the vaporized alcohol and some water\flavor to rise up and enter into the lyne arm. The neck is often narrower at the top than the bottom allowing for non-ethanol components to condense on the walls and fall back down into the wash. However, as you have probably noticed this is not how the still in the above image is configured. This just demonstrates the vast amount of variation in each design.
Lyne Arm: The lyne arm will affect the amount of non-ethanol components that make it into the distillate. For example, as the vapors rise up the neck and into the lyne arm the temperature becomes cooler and the less volatile compounds (water, flavor, etc.) will change from a gas state to a liquid state (condense). If the lyne arm is ascending at a 45 degree angle those compounds will flow back down into the wash. This will give you a ‘lighter’ flavor and higher alcohol content in the final product. On the other hand if the lyne neck was angled down at a 45 degree angle the less volatile compounds will condense and drip down into the condenser, along with the ethanol vapors thus giving the distillate a more flavorful, ‘fuller’, taste.
Condenser: The condenser cools the ethanol vapors to a temperature that is less than their boiling point. Thus, it condenses the vapors back to liquid. Condensers can be cooled by the ambient air temperature, flowing air (a fan) or water. With a water-cooled condenser the cold water will be pumped through a coil, as in the diagram below, or around the outside of the tube that carries the ethanol vapors. Different designs will utilize different methods. The key is to cool the vapors so they drip into a collection container as opposed to escaping into the air.
It is up to the distiller to experiment with different mash recipes, still shapes and configuration to produce the end product that has been envisioned. Bottom line: Take notes, take your time, have fun and experiment.