Pot Still
A pot still is made of copper, featuring a wide base and a narrow neck. When the wash is heated in the pot still, alcohol evaporates first due to its lower boiling point than water. The alcohol vapour is then cooled through the condenser, where it turns into liquid, resulting in a higher percentage of alcohol.
Pot stills utilise batch distillation, which operate in distinct cycles. This means that a specified amount of wash goes into the still and gets distilled into a spirit. After each batch, the still is emptied, cleaned, and refilled for the next distillation.
Pot stills produce spirit with robust and complex flavours. They are commonly used to make single malt Scotch whisky.
Column Still
A column still, also known as Continuous still or Coffey still, is another type of distillation apparatus. It is named after Aeneas Coffey, who invented and patented the design in 1830.
Column stills operate on the principle of continuous distillation, which means the wash is continuously pumped into the still, while a consistent flow of distilled spirit is collected on the other side.
Column stills consist of a tall column with multiple trays, each slightly cooler than the one below. The continuous flow of steam, as a heat source, removes heavier compounds such as fusel oil and impurities from the wash, and causes the purer spirit to rise to the top.
Column still is mainly used to produce single grain and blended whiskies.
Double Distillation
Scotch whisky is distilled twice. During the first distillation, the alcohol and some water are separated from the wash, also known as low wines, yielding an Alcohol by Volume (ABV) around 21-30%.
The collected low wines then undergo a second distillation, resulting in a purer, more concentrated spirit with an ABV of 70% or higher.
Making The Cut: Heads, Hearts, And Tails
The spirit obtained from the still can be separated into three parts: Heads, Hearts, and Tails.
During the distillation process, the initial and final portions, known as the ‘heads’ and ‘tails’, are discarded as they contain unwanted impurities, off notes, and volatile compounds. Distillers collect the ‘hearts’, which is the most desired part of the spirit, and later mature it in oak casks to develop into whisky.
