Whisky Magazine Issue 23
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Ian Wisniewski investigates the effect this enigmatic metal has on the finished product - whisky
A mellow, gleaming colour that exemplifies ‘industrial aesthetics' is an initial, superficial evaluation of copper. Now, let's slip into our anoraks and take a closer look. Being highly malleable, copper is a perfectly compliant medium, however idiosyncratic the shapes and dimensions of pot stills stipulated by distilleries. As copper's thermal conduction properties exceed every inexpensive metal, stills can be heated very quickly, while also offering the opposite quality, being able to cool rapidly. Moreover, copper is the best option for dissipating heat at a uniform temperature, preventing ‘hot spots' from accumulating (always a concern with direct-fired stills).
But such assets are only supplementary benefits when compared to copper's essential role during distillation, and subsequently maturation, which assists malt whisky in attaining its distinct, characteristic flavour.
During distillation copper absorbs sulphur compounds, converting them into other, less organoleptically active compounds (ie. less sulphur character), while also acting as a catalyst helping to manipulate the ester character. As sulphur compounds feature a distinctive line-up of notes, ranging from struck match, sulphurous, rubbery, meaty and sweaty socks, to cabbage and vegetal, they can easily dominate and ‘conceal' other characteristics within the new make spirit. While a certain level of sulphur character can be highly desirable, depending on the house style, lowering the level of sulphu...