Pot still

A pot still is the method used in distilling spirits such as whisky or brandy along with other more ‘artesian’ type spirits that are intended to portray a more unique character and reflect the product and area of origin. Pot-distilled liquor comes from the old-fashioned copper pot with the big coil attached to it — basically, the moonshiner's still of popular iconography. 

Heat is applied directly to the pot containing the wash (for whisky) or wine (for brandy). This is called a batch distillation.

Alcohol boils at approx. 78 °C (172 °F), while water boils at 100 °C (212 °F). During distillation, the vapour contains more alcohol than the liquid. When the vapours are condensed, the resulting liquid contains a higher concentration of alcohol. In the pot still, the alcohol and water vapour combine with esters and flow from the still through a condensing coil. There they condense into the first distillation liquid, the so- called "low wines". The low wines have a strength of about 25- 35% alcohol by volume, and flow into a second still. 

It is then distilled a second time to produce the colourless spirit, collected at about 70% alcohol by volume. Colour is added through maturation in an oak aging barrel, and develops over time.

Below is a great animation that can help to highlight some of the main factors in whiskey production. In many cases the process may vary, but overall this video outlines the fundamentals. To view the original click HERE.

Continuous Distillation

An uninterrupted distillation process where a continuous flow of distillate is collected as output. The raw material may be continuously fed into the still at one point or reloaded without interrupting the collection of distillate.

When performing a batch distillation using the simple distillation process the still needs to be continuously emptied of the spent material and refilled for each individual distillation run, interrupting the collection of the distillate. This is not so for continuous distillation as there are no interruptions in the distillation process.

A prime example of continuous distillation is the professional Armagnac Type Alembic Still with which high grade alcohol can be obtained in a single run which would normally require double or triple distillations using the simple distillation technique. In the fractional column a continuous feed of an alcoholic solution such as wine is introduced in the column. As this solution comes into contact with the hot rising vapours, from the boiler, the more volatile components are stripped from the solution and rise up the column. These alcohol vapours are drawn off and condensed after continuous rectifications (discussed further in the fractional distillation method). The more dense components or the less volatile components of the alcoholic solution stream back down into the boiler.

Fractional and continuous distillations methods are only descriptive of the various processes that take place and all may be incorporated into a single still design.

The graceful Charentais Alembic Still developed in France in the early 16th century to distil fine cognacs from Charentais wines is a semi continuous distillation process as you may allow for a continuous feed of wine for distillation. This unit is comprised of an alembic pot attached to an onion shaped dome or preheater and condensing unit. The wine to be distilled in this case is preheated in the onion shaped dome by the flow of vapour from the swan neck tubing of the alembic pot as it flows in the direction towards the condenser unit. The wine in the preheater in turn is transferred to the alembic pot via a connecting tube between the two for distillation, thus closing the circuit.

The Portuguese Arrastre de Vapour distilling system is yet another example of a semi continuous distillation design. This system is very versatile and may be constructed according to the clients' specific needs. A two or more column system allows for continuous drawing off of distillate as while one column is emptied and refilled the distillation process continues in the second column.

Professional continuous distillation systems have obvious applications for large scale high grade alcohol production with unlimited potential for producing any number of alcoholic spirits. The hobbyist distiller may want to experiment with the Charentais Alembic Still, fully functional yet beautiful in design. The Portuguese Arrastre de Vapour is a multi-purpose distilling system, due to its versatility, and may be used for the distillation of spirits, essential oils, medicinal herbal extracts, perfumes, rosewater etc.