Two of three copper pot stills at Locke’s Distillery, Kilbeggan, Westmeath, Midlands, Ireland, which were installed in the late 1970s. These were recovered from the Tullamore Dew Distillery before it was demolished in 1990 to make way for a shopping mall and carpark. Originally, there were four similar copper stills at Locke’s but sadly these were broken up for scrap in 1974 during which time the old distillery also lost some other internal fittings and equipment. Fortunately, most remained and ensured the authenticity of the place as a working industrial museum.
The copper stills similar to the originals once at Locke’s in Kilbeggan, were produced by Millars & Co Ltd of Church Street, Dublin.
A column still, also called a continuous still, patent still or Coffey still, is a variety of still consisting of two columns.
The first column (called the analyzer) in a column still has steam rising and wash descending through several levels. The second column (called the rectifier) carries the alcohol from the wash, where it circulates until it can condense at the required strength.
Column stills behave like a series of single pot stills, formed in a long vertical tube. The tube is filled with either porous packing or bubble plates. The rising vapour, which is low in alcohol, starts to condense in the cooler, higher level of the column. The temperature of each successively higher stage is slightly lower than the previous stage, so the vapour in equilibrium with the liquid at each stage is progressively more enriched with alcohol. Whereas a single pot still charged with wine might yield a vapour enriched to 40-50% alcohol, a column still can achieve a vapour alcohol content of 96%; an azeotropic mixture of alcohol and water. Further enrichment is only possible by absorbing the remaining water using other means, such as hydrophilic chemicals or azeotropic distillation.
A column still is an example of a fractional distillation, in that it yields a narrow fraction of the distillable components. This technique is frequently employed in chemical synthesis; in this case, the component of the still responsible for the separation is a fractionating column.
A continuous still can, as its name suggests, sustain a constant process of distillation. This, along with the ability to produce a higher concentration of alcohol in the final distillate, is its main advantage over a pot still, which can only work in batches. Continuous stills are charged with preheated feed liquor at some point in the column. Heat (usually in the form of steam) is supplied to the base of the column. Stripped (approximately alcohol-free) liquid is drawn off at the base, while alcoholic spirits are condensed after migrating to the top of the column.
Column stills are frequently used in the production of grain whisky and is the most commonly used type of still in the production of Bourbon and other American whiskeys. Distillation by column still is the traditional method for production of Armagnac, although distillation by pot still is allowed. The use of column stills for the distillation of Cognac is forbidden. Distillation by column stills are permitted for Calvados AOC and Calvados Domfrontais. Calvados Pays d’Auge AOC is required to be distilled by pot still.
John Locke’s distillery at Kilbeggan in County Westmeath is a working industrial heritage museum set up and run by local volunteers of the Kilbeggan Preservation and Development Association Ltd since 1982. In 1987 the site was bought by Cooley’s Distillery and in 2010 also secured the lease for the visitor’s centre there. To celebrate their one-millionth visitor, Locke’s Distillery Museum held a free open-day on 10th September 2011 which was well attended and a great success. Incidentally, the one-millionth visitor came from Germany.
Locke’s Distillery produces pure Pot Still Irish whiskey as well as having some 40,000 sq. ft. of storage space at Kilbeggan, also used for the storage and maturation of whiskey produced by Cooleys. Kilbeggan is also unique in having a 180 year old licensed pot still with a capacity to produce 25,000 cases a year of pot-still whiskey, most of it going to export. Since 2010 Kilbeggan distillery has also introduced its own full milling, mashing, fermentation and distillation processes carried out using more traditional methods.