Mash Tun: The Whisky Mashing Vessel | Scottish Delight

The mash tun is the vessel in which crushed barley (grist), or other grains (like rye or corn, in case of Bourbons or whiskeys) and hot water are mixed in order to extract the soluble sugars from the barley. It typically will be round, topped with a copper or stainless steel dome, although there also are versions that do not have a cover (like the one at Bruichladdich). The base of the tun contains small openings, sort of like a sieve, which can be used to extract the sugary water (now called wort) while ensuring the grain stays behind.

The mashing process

During the mashing process, water of increasing temperatures will be added to the grist in 3 or 4 phases. The first phase, water at a temperature of roughly 64 degrees Celsius (147 Fahrenheit) is used for a period of some 30 minutes. After the 30 minutes, the water is drained (and stored in the worts receiver (or underback)), after which a second batch of water at a temperature between 70 and 75 degrees Celsius (158 – 167 Fahrenheit) is added. The water is given time to absorb the sugars for a while again, and then drained and added to the initial batch collected in the worts receiver. The remainder of the grain is then removed and usually sold off as cattle feed. There are several types of tuns in use, and we will discuss them in a bit more detail.

Traditional mash tun

The traditional mash tun had a rotating arm in the middle, equipped with rakes that stir up the grain in the bottom of the tun to help extract the sugars and make it easier to drain the waters.
The Traditional Mash Tun at Springbank
The Traditional Mash Tun at Springbank

Semi-lauter Mash tun

From the 1970s and onward, the traditional vessels started getting replaced with mash tuns that sport long vertical iron knives, themselves equipped with small blades (or fins). In a semi-lauter version, the knives are rotated around in the mash tun by a spindle in the middle. The blades are able to disturb the malt much more than the traditional rakes, and thus increase the speed of the mash process.

Full lauter mash tun

The Full lauter mash tun is very similar to the semi-lauter version, but here, the knives don’t just rotate, but can also move up and down in order to further stir the mix.
The mash tun at the Tomatin distillery
The mash tun at the Tomatin distillery
  Some manufacturers of mash tuns include the now closed Newmill Engineering (who made the mash tuns at Ardbeg, Speyside distillery, Glenlossie, among others) and German Steinecker (who fitted Craigellachie, Aberlour, Glen Elgin and others).

Frequently Asked Questions

What is a mash tun used for in whisky production?

A mash tun is the vessel where crushed barley (grist), or other grains like rye or corn for bourbons and other whiskeys, is mixed with hot water to extract the soluble sugars. The base contains small sieve-like openings that let the resulting sugary liquid, called wort, drain out while keeping the grain behind.

How does the mashing process work?

Water is added to the grist in three or four phases at increasing temperatures. The first phase uses water at around 64°C (147°F) for about 30 minutes, after which it’s drained into the worts receiver (or underback). A second batch of water at 70–75°C (158–167°F) is then added, given time to absorb more sugars, and drained into the same receiver alongside the first batch.

What happens to the leftover grain after mashing?

Once the sugars have been extracted, the remaining grain is removed from the mash tun and is usually sold off as cattle feed.

What is the difference between a traditional, semi-lauter, and full lauter mash tun?

A traditional mash tun has a rotating arm with rakes that stir the grain to help extract sugars and ease draining. From the 1970s onward, many distilleries switched to semi-lauter mash tuns, which use vertical iron knives fitted with small blades that rotate around a central spindle, disturbing the malt more and speeding up the process. A full lauter mash tun is similar to the semi-lauter design, but its knives can also move up and down for even more thorough stirring.

Do all mash tuns have a cover?

Most do, typically topped with a copper or stainless steel dome, but some distilleries use uncovered mash tuns, such as Bruichladdich.

Which distilleries are known for particular mash tun equipment?

Newmill Engineering, now closed, built mash tuns for distilleries including Ardbeg, the Speyside distillery, and Glenlossie, while the German manufacturer Steinecker fitted mash tuns at Craigellachie, Aberlour, Glen Elgin, and others. The traditional rake-style mash tun at Springbank and the mash tun at the Tomatin distillery are also notable examples.