The manufacture of malt whisky


[Kilns] Traditionally, the barley is first soaked with water, then spread over a large floor and allowed to germinate. The germination produces sugar and thus converts the barley into malt. As the germination releases heat, the barley has to be turned regularly, and the temperature controlled.

Then the malt is transferred to the kiln, spread over a mesh and dried over a fire. Some peat may be added to the fire in order to strenghten the peaty taste noticeable in many malt whiskies. The pagoda-shaped roof of the kiln, which acts as a chimney, is a very distinct architectural feature of whisky distilleries.

Today, most distilleries buy their malt from industrial maltings, but even if the kiln thus has lost its original function, it is still retained and sometimes used for other purposes (e.g. at Cardhu as visitor centre). On the picture you can see the two pagoda-shaped roofs of the kilns of the Bowmore distillery, which are still in use.


[Mash Tun] Next, the malt is coarsley ground and becomes known as malt grist. In the mash tun it is mixed with hot water, in which the malt sugars are dissolved. The resulting sweet solution is called wort. While the solid residue of the malt is sold as cattle food, the wort is cooled, and yeast is added. In big tanks, called washbacks, the fermentation then takes place, yielding a 'beer' with some 8--10 percent alcohol, the wash.

[Washbacks] The pictures show the mash tun (above) and the washbacks (left) at the Bowmore distillery.


[Pot Stills] Distillation takes place in onion-shaped pot stills made from copper. In the first distillation, which takes place in the wash stills, the alcohol fraction is raised to somewhat over 20 percent. The product, called low wines, then is distilled a second time in spirit stills, which results in a spirit with over 60 percent alcohol. In the picture you can see the stills of the Laphroig distillery. Note the different shapes of the wash stills (in the background) and the spirit stills (in the foreground).

In the distillation process, the first and the last fraction (foreshots and feints) are recycled back for re-distillation, while only the middle cut via the spirit safe goes to the spirit store to be filled into barrels. Originally the spirit safe was locked by the Excisemen, but now the distilleries themself are responsible for paying the correct amount of taxes ... below you can see the spirit safe of the Bowmore distillery.

[Spirit Safe]


By law, the spirit can only be called 'whisky' after at least three years of maturation. Usually no new casks are used, but rather casks which have been used before to mature Bourbon or Sherry. Some distilleries use only one of both types, others use both Sherry and Bourbon casks. Also in some distilleries the casks are charred before use, which helps to release vanilla from the wood. In the picture you can see one of the warehouses of the Cardhu distillery, where the casks are stored.



Once maturated, the whisky is bottled. To achieve a more uniform taste, usually many casks are blended (as opposed to single cask whiskies, which are bottled from a single cask only).

Also, many manufacturers filter the whisky at low temperatures (about +5 to -5 deg Celsius) to remove fat particles. The manufacturers of course argue that this does not affect the taste, but there are dissenting opinions ...

And finally, many whiskies are colored with caramel to achieve a "uniform color" (in the EU, this must be declared, so you should be able to tell from the bottle whether your favourite whisky is coloured).

If you don't like filtered and/or colored whisky, you should look for products from independent bottlers.