A Whisky Patent Still
The patent or continuous still was invented at the beginning of the 19th century, when the commercial potential of various types of spirits began to be recognised. As the operation of the pot still requires time and skill, several versions of a still that simply went on producing, making spirits quickly and on a large scale were evolved. The most famous name in the history of this type of distillation is that of Aeneas Coffey, whose name is often used for the still that he patented in 1831. Although pot stills are often used for part of the production of certain spirits, it is the patent or continuous still that makes possible the large-scale manufacture of gin, whiskey (not Irish) and vodka.
In very general terms, the liquid to be distilled is trickled down from the top of a tall column – made of copper, like the pot still – through various sections. During this process it is vaporised by the heat of steam pushed into the still. These vapours then rise to the top of this part of the still and subsequently pass into the rectifier, another column of perforated copper plates alongside the analyser or first still. Once again the vapour are forced to the top of the column and are directed off at the top, while any impurities remain at the bottom. The process, which varies according to the type of spirit being made, is complex but not difficult to understand if one can visit a distillery, see the columns, and realise what is going on inside which. These columns can be very large, like huge copper chimneys, or of modest size.