Like Scotch malt whisky is usually distilled twice,and occasionally three times,using batch distillation in copper pot stills .During the last distillation compounds with the lowest boiling points,called foreshots (or head),boil first.then comes the heart(middle cut),then the feints(tails) leaving liquid called spent lees in the still.its the heart that is collected and aged to become whisky.
First Distillation
The first distillation takes place in a ‘wash’ still where the alcohol in the wash is separated by heating,because alcohol boils at a lower temperature than water(78.37°C/165°F versus 100°C/212°F) so the spirit vaporises before the water and rises up the neck of the still until the spirit vapour reaches the top and is directed through the swan neck,along the lyne-arm to the condenser.
Second Distillation
The second distillation is the same principles apply as in the first distillation but with more of the water being left behind as the alcohol vaporises up the still ,but as there are no solids in the still to start as these have already been removed by the first distillation,frothing is not an issue,so spirit stills dont have sight glasses in their necks.
In the scond distillation,and sometimes also a third distillation(in the case of Auchentoshan and Hazalburn),the distiller exercises considerable control over the character of the final distillate.The distiller’s art is knowing when to ‘make the cut’.Different flavouring agents evaporate at different temperatures and the distiller has to find the right balance .
