What is a wash still and a spirit still?

Scotch malt whisky is distilled in two stages, and each stage has its own copper still: first the wash still, then the spirit still. The first still extracts the alcohol from the fermented wash, the second turns it into a distillate that is clean and strong enough to go into the warehouse. According to the British rules, single malt Scotch whisky must be distilled in batches in pot stills, at a single distillery, from water and malted barley without other grains. Two stills is therefore the usual set-up, not a fashion: in a single pass you do not reach the strength and purity that are required. The wash still is almost always the larger of the two, because the full quantity of liquid goes into it. At Old Pulteney, for example, a maximum of 21,707 litres goes into the wash still and 17,343 litres into the spirit still.

The wash still receives the wash, the fermented mash with about 7 to 8 percent alcohol, and distils it up to low wines of roughly 21 to 30 percent. Alcohol boils at a lower temperature than water, so the alcohol vapour rises first. The vapour travels through the neck and the lyne arm to the condenser, where it becomes liquid again. What remains in the still is almost free of alcohol and is drained off; in Scotland that residue is concentrated into cattle feed. The wash still therefore does the rough work: separating, not refining. How hard the distillery heats the still already counts here. Heating quickly speeds up the distillation and gives a heavier distillate, while distilling slowly produces a finer, lighter stream.

The spirit still distils the low wines once more and delivers new make spirit, the clear distillate of around 70 percent that then goes into cask for years. A spirit still run takes about six hours and falls into three parts. First come the most volatile compounds, the foreshots or heads, which are unwanted. Then follows the heart, the middle cut, and that is the only part that ends up in the cask; many distilleries cut at around 71 to 72 percent. At the end come the heavy, oily feints or tails. Where exactly the cut is made is decided by each distillery itself, and that is where a large part of the house character lies. Esters with a fruity aroma are found mainly in the distillate drawn off at higher strength, around 68 to 72 percent, while heavy fatty acids come along as soon as the cut runs on to about 58 percent.

Heads and tails do not disappear, but go to the low wines and feints receiver and are distilled again with the next charge of the spirit still. The low wines from the wash still also go into that same vessel. The spirit still is therefore never filled with only fresh low wines, but with a mixture of fresh low wines and the recovered heads and tails from the previous run. This way hardly any alcohol is lost and the distillery gets an even charge, run after run. That also explains why the heart is defined so tightly: what falls outside the cut is not waste but raw material for the next round.

Shape, height and the angle of the lyne arm determine how much vapour falls back into the still on the way, and that falling back, called reflux, makes the distillate lighter or heavier. A long, narrow neck gives a lot of reflux: the heavy, oily compounds condense and sink back, leaving a light, floral stream. The very tall stills of Glenmorangie are known for this. A short, wide neck lets more heavy substances through and yields a fuller, creamier and oilier distillate. Other devices also play a part: a boil ball or bulbous chamber between pot and neck increases the reflux, a narrowed waist as at The Glenlivet does the same, and a lyne arm that slopes upward sends heavy compounds back before they reach the condenser. Wash still and spirit still work differently here: the wash still forms the raw distillate, the spirit still refines it.

De wet stelt twee grenzen en geen aantal: Scotch moet van de ketel komen op minder dan 94,8 procent vol en wordt afgeleverd op minstens 40 procent vol. Zo staat het in regulation 3 van de Britse Scotch Whisky Regulations 2009, en in vrijwel gelijke woorden in de Europese verordening 2019/787, die eist dat elke afzonderlijke distillatie onder 94,8 procent vol blijft. Hoe vaak er gestookt moet worden, schrijft geen van beide voor. Schotse malt whisky gaat meestal twee keer door de ketel en soms drie keer. Bij Irish Pot Still Whiskey is drie keer stoken juist de traditie, al verplicht het technisch dossier dat niet en wordt er ook dubbel gestookt. Alcohol verkopen wij alleen aan personen van 18 jaar en ouder: NIX18.