What the wash still and spirit still each do

Two stills, two jobs

Malt whisky is usually distilled twice in copper pot stills. The first still is the wash still. It takes the fermented wash, a strong unhopped beer of around 8% ABV. It pulls out most of the alcohol. The second is the spirit still. It refines that first distillate into new make spirit, the clear liquid that goes into casks to become whisky.

Distilling works because alcohol boils at a lower temperature than water, about 78 °C against 100 °C. Heat a mix of the two and the vapour carries more alcohol than the liquid it came from. Condense that vapour and you have a stronger liquid. Do it twice and you go from about 8% to about 70%.

The wash still strips the alcohol

The wash still is usually the larger of the pair. It is filled with wash and heated, today mostly by steam coils or pans inside the still, though some distilleries still heat directly. As it boils, vapour rises, passes through the neck and lyne arm and condenses. The liquid that comes off is called low wines, typically somewhere around 20% to 25% ABV.

The still runs until almost all the alcohol has left the wash. What remains in the pot is pot ale, a hot, sour, yeasty liquid with very little alcohol, which is treated or turned into animal feed. The wash still is not choosy. Its job is to collect the alcohol and much of the flavour while leaving the solids and most of the water behind.

One practical worry is foam. Wash contains yeast, protein and some solids. It can froth up into the neck when it boils. Stillmen watch a sight glass and control the heat to keep foam out of the lyne arm.

The spirit still makes the cuts

The spirit still is filled with low wines, plus the foreshots and feints saved from the previous spirit run. Here the stillman decides which part of the distillate becomes whisky. The run is split into three parts:

• Foreshots come first. They are high in volatile compounds and are not kept as spirit.
• The heart, or middle cut, is the new make spirit that goes to cask.
• Feints, or tails, come last. They carry heavier, oilier compounds and are not kept as spirit.

Foreshots and feints go back into a later spirit still charge, so their alcohol is not wasted. Where the stillman cuts from foreshots to heart and from heart to feints shapes the spirit more than almost any other single decision. Our guide to low wines and the spirit still charge follows the recycling.

What comes off at the end

New make from a spirit still is usually collected at an average of roughly 65% to 72% ABV. It is clear, often fruity, cereal or floral. It is also quite fierce. It is not yet whisky. In Scotland it must spend at least three years in oak casks before it can be called Scotch whisky. Many spirits rest far longer. In India, heat speeds up the interaction with wood, so casks mature faster and lose more to evaporation each year.

Different cuts make very different spirits from the same low wines. Our guide to running a spirit still for a lighter or heavier spirit shows how.

Why not do it in one still?

A single pot still run cannot go from 8% to 70% in one pass. Nor can it separate foreshots, heart and feints cleanly while also dealing with the foam and solids of the wash. Splitting the work means the first still can be robust and the second precise. Column stills work differently and can reach much higher strength in one continuous pass, which is how most grain whisky and neutral spirit is made. Our guide to double distillation explained goes a step further.

What to notice on a distillery visit

On a tour, look for the spirit safe, the brass and glass box where the stillman watches the spirit flow and switches it between receivers. That box is where the cuts happen. Notice which still is bigger, how the necks differ and how warm the stillhouse feels. If tastings are offered, keep pours small, take water and never drink and drive.

Knowing what each still does is the start. Knowing why a stillman cuts where they do is the craft. It is what a structured course spends real time on.

Your first step

Next time you taste a malt whisky, look up whether it was double or triple distilled and what kind of stills the producer uses. Then taste it with that in mind. You will start to link a lighter or heavier spirit to the stillhouse, not only to the cask.

Common questions

What is the difference between a wash still and a spirit still?

The wash still strips alcohol from the fermented wash to make low wines of about 20% to 25% ABV. The spirit still redistils low wines and the stillman cuts out the heart as new make spirit.

What are low wines?

Low wines are the distillate from the wash still, typically around 20% to 25% ABV. They are the main charge for the spirit still.

What happens to foreshots and feints?

They are collected and added back into a later spirit still charge, so their alcohol is recovered.

How strong is new make spirit?

New make from a pot still is usually collected at an average of roughly 65% to 72% ABV.