A patent still distillation is a method of producing grain whiskey through a continuous distillation process. It is also called a “Coffey” still, from the name of Aeneas Coffey, who patented the idea in 1831, according to the Scotland: Whisky and Distilleries website.
The approach pushes hot steam into a vertical tall container containing a mixture of mashed grains and yeast. The alcohol vapors emanating from the boiling mix escape to an adjacent vertical reservoir and condense back into nearly pure liquid alcohol, according to the University of Edinburgh
The aroma of this distilled whiskey is generally lighter than other whiskeys. It matures in a shorter period of time and its light character blends well in mixed drinks.
This process operates continuously, in contrast to other methods that run in batches. This method is more efficient and less expensive.
The boiling temperature of the wash is not high enough to eliminate contaminants such as methanol and acetaldehyde that may cause organ disease when consumed in large quantities.
This efficient and economical distillation approach revolutionized the whiskey production in the 1830s and placed Scotland and Northern Ireland as the prime producers of whiskey in Europe. This type of production is still in use today.
References and ResourcesScotland: Whisky and Distilleries - History
University of Edinburgh: Whisky Term Definitions
Resources"The Art of Distilling Whiskey and Other Spirits"; Bill Owens; 2009
"The Secrets of Building an Alcohol Producing Still"; Vincent R. Gingery; 1994
Chest of Books: Diagram of Coffey Still