Whisky Magazine Issue 115
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We look at what copper has to offer and the science behind it
What an amazing metal. Copper is highly malleable and complies readily with the shapes of pot stills (however idiosyncratic) stipulated by distilleries. Exemplary thermal conduction properties enable the stills to be heated very quickly (saving energy), but copper also has a significant influence on the character of the new make spirit. Exactly how influential the copper is depends on various factors, including the size and shape of the stills and the rate of distillation (which varies among distilleries). Typically, the greater the influence of copper the more elegant the resulting spirit, while less influence promotes a fuller-bodied spirit. During distillation the charge (ie. alcoholic liquid) is heated and begins to vapourise. As vapours ascend the neck of the still the temperature becomes relatively cooler, causing vapours to condense when they meet the copper surface. Meanwhile, heat from these vapours also transfers to the copper surface, increasing the temperature of the copper. This results in the liquid re-boiling and vaporising, in a virtually instantaneous process. Vapours then rise from the copper surface and continue ascending the neck, where the temperature is (once again) relatively cooler, and the process of condensing, re-boiling and vapourising repeats. This process may occur numerous times before the vapours reach the top of the neck, where a pipe conducts them to the condenser (to condense into liquid). Each time vapours are in contact with the copper ...