What is Patent Still distillation?

Unlike Malt Whisky, Grain Whisky is distilled in a continuous operation in a Patent Still. This is sometimes known as the Coffey Still. after Aeneas Coffey, who developed it in 1831.

Steam is fed into the base of the analyser and hot wash into the top. As the two meet on the surface of the perforated plates, the wash boils and a mixture of alcohol vapours and uncondensed steam rises to the top of the column. The spent wash runs down and is led off from the base.

The hot vapours enter the rectifier at the base and as they rise through the chambers they partially condense on the sections of a long coil through which wash is flowing. The spirit vapour condenses at the top of the rectifier and is run off through a water-cooled condenser to the spirit safe. Once the spirit begins to be collected it runs continuously until the end of distillation.

Because of the rectifying element present in this process, the distillate is generally lighter in aroma than most Malt Whiskies. It consequently has a milder character and requires less time to mature.

© SWA 1995