Double distillation explained
Double distillation is the standard method for malt whisky in pot stills. The wash goes through two copper stills, one after the other. Here is what happens at each stage and how it shapes what you taste.
Two runs through copper pot stills
Double distillation means running the fermented wash through two pot stills in turn. The first, the wash still, turns a wash of around 8% ABV into low wines of roughly 20% to 25% ABV. The second, the spirit still, redistils those low wines into new make spirit, usually collected at an average of around 65% to 72% ABV.
It is the norm for Scotch malt whisky and common for malt and pot still spirits around the world. Some Irish and a few Scottish distilleries add a third distillation, which we cover in triple distillation explained.
Why distilling concentrates alcohol
Alcohol boils at about 78 °C and water at 100 °C. When a mix of the two boils, the vapour holds a higher share of alcohol than the liquid. Condense the vapour and you have a stronger liquid than you started with. A single pot still pass roughly triples the strength, which is why one pass takes 8% wash to around 20% to 25% low wines. A second pass takes those low wines up near 70%.
Distillation also separates flavour compounds. Some, such as many esters, are volatile and come over early. Others are heavier and come over late. That is what lets the stillman shape the spirit by choosing what to keep.
The first run gathers everything
In the wash still, the aim is to collect almost all the alcohol and leave behind the water, yeast and solids. The run goes on until the distillate is very weak. The stillman watches for foam, which can rise from the protein and yeast in the wash. Little selection happens here. The low wines carry nearly all the alcohol and a wide range of flavour compounds.
What is left in the wash still is pot ale, which has very little alcohol and is treated or sold as animal feed.
The second run chooses the spirit
The spirit still is where the decisions are made. Low wines are mixed with foreshots and feints saved from earlier runs and distilled again. The distillate is split into three parts. Foreshots come first and are set aside. Then comes the heart, the new make that will go into cask. Last come the feints, heavier and oilier, which are also set aside.
The cut points are measured by strength and judged by smell. A typical heart might run from somewhere in the mid 70s down to the mid 60s ABV, but every distillery has its own points. Cutting to feints earlier gives a lighter, fruitier spirit. Cutting later keeps more heavy, oily and smoky character. Our guide to what the wash still and spirit still each do explains the cuts in more detail.
How double distillation shapes flavour
Compared with a column still, which can run continuously to very high strength, two pot still runs leave much more flavour in the spirit. New make from a double distilled malt is often fruity, malty and full bodied, with some oily weight. Compared with triple distillation, it is usually heavier and more robust, because the third run strips more of the heavier compounds.
The shape of the stills, the speed of the run and the type of condenser all change that baseline. Two distilleries using double distillation can make very different spirits. Our guide to batch versus continuous distillation compares pot and column stills.
A note for Indian drinkers and distillers
Many Indian single malts follow the same double pot still method used in Scotland, with the main differences coming in maturation. Indian heat speeds up the reaction between spirit and oak and raises the yearly loss to evaporation well above the commonly quoted figure of about 2% for Scotland. A double distilled spirit with plenty of body can stand up well to that faster, more intense cask influence.
For a craft distiller, the craft of double distillation lies mostly in the spirit still: reading strength and aroma together and holding cut points steady batch after batch. That is a hands on skill built on a clear understanding of what the still is doing.
Taste the difference yourself
Find one double distilled malt whisky and one triple distilled whiskey. Pour 15 ml of each, add a few drops of water and nose them side by side. The triple distilled one is usually lighter and more delicate. Try to describe what is missing from it rather than what is there. Drink water between them and never drink and drive.
Common questions
What does double distilled mean?
It means the spirit was distilled twice, first in a wash still to make low wines and then in a spirit still to make new make spirit.
Is all Scotch double distilled?
Most Scotch malt whisky is double distilled in pot stills, but a few distilleries use triple distillation. Scotch grain whisky is usually made in column stills.
Does double distillation make whisky smoother?
Each distillation removes some compounds and concentrates others. Double distilled spirit usually keeps more body and weight than triple distilled spirit.
How strong is double distilled new make?
New make from a spirit still is usually collected at an average of roughly 65% to 72% ABV.
