Single malt scotch whisky still distillation equipment Scotch malt whisky is usually distilled twice, and occasionally three times. It is distilled in copper pot stills like this. During the last distillation compounds with the lowest boiling points, called foreshots (or heads), boil first. Then comes the heart (middle cut), then the feints (tails) leaving liquid called spent lees in the still. It's the heart that is collected and aged to become whisky. Alcohol produced by fermenting malted barley contains natural sulphur compounds that if allowed in the final whisky in too large a concentration will "impair flavour. Copper reacts with the sulphur in the alcohol vapour produced during distillation to form harmless copper sulphate which can easily be removed by filtration (this is the green substance often seen forming in spirit safes). Parameters Item Name…