It is difficult to say precisely where and when distillation was invented. Certainly, we know is that small ceramic stills dating from the second century BC have been found.
These stills contained the three essential elements for distillation: the container placed above the hearth, the tube to transport the alcohol vapors, the condenser.
In the fourth century, distillation was practiced to produce medicinal and aromatic plants. Subsequently, the Arabs will diffuse distillation techniques.
In the Middle Ages, brandy is produced in small quantities in small glass or ceramic stills.
The use of copper, advocated by Savonarola in the fifteenth century, significantly changed the use of the still.
The copper is a great conductor of heat, it will remove sulfur compounds, and it is an easy metal to work with. When distilling in copper, the copper reacts on a molecular level with the sulfurs put out by the fermenting yeast. It “cancels-out” the sulfur taste which would otherwise be bitter and not as smooth.
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 a thorough cleaning of the copper still, the copper sulfate is washed down the drain, and not into the rum.
The copper stills will produce a much greater alcohol capacity.
The charentais stills evolved in the Cognac region of France in the early XVI century when the acidy white Charente wines from this region were first distilled into brandy.
The Charentais copper still comprises a characteristically shaped boiler set over direct heat; a still head shaped like a turban, an olive, or an onion; and a swan’s neck tube that continues to become a coil, passing through a cooling tank referred to as the “pipe.”
With pot stills the process is a discontinuous distillation process. Each “batch” (or “cuvée” in French) is distilled individually because the residue must be cleaned out after each cotta.
The distillation is generally carried out in two stages in a pot still.
In the first distillation the fermented liquid is put into the boiler which is heated either directly by fire or by steam-heated coils. At this stage the liquid contains yeast, crude alcohol, some unfermentable matter and the by-products of fermentation. Volatile substances, such as methanol, evaporate first. During the process of boiling the wash, changes take place in its constituents which are vital to the flavour and character of the rum.
As the wash boils, vapours pass up the neck of the still and then pass through a water-cooled condenser or a worm, a coiled copper pipe of decreasing diameter enclosed in a water jacket through which cold water circulates. This condenses the vapours and the resulting distillate, known as low wines, is collected for re- distilling. The liquor remaining in the boiler is known as burnt ale.
This distillate, called “low wines” has a concentration of about 25–35% alcohol by volume.
During the second distillation, the initial and final portions of spirit which condense (termed the heads and tails respectively) may be captured separately from that in the centre or “heart” of the distillation. This is because these portions of the distillate may contain high concentrations of methanol (which is toxic), or other congeners (which it may be desirable to keep out of the final distillate for reasons of style or taste).
At the end of second distillation, rum has a content alcohol between 65 and 75%.
Head and tail will be redistilled in the next batch.
The Pot Still has changed little in general design over the centuries. Until the 19th century, the pot still was the only type of still used.
The success of the distilling cycle lies in constant monitoring, close attention and extensive experience on the part of the distiller, who intervenes in the distillation techniques and especially on the choice of the “cutting points” (fractions that the distiller eliminates, heads and tails), thus stamping his or her personality of the rum.