Whisky 'machinery' - the Mash Tun

A new series looking at some of the 'machinery' used in a distillery to create whisky - this time the Mash Tun.

I've covered the basic process of creating whisky here, but I'm going to explore the machinery a little more in this series.

Once the barley had been ground into grist by the Malt Mill it's poured into a Mash Tun and hot water is added to dissolve the sugars creating wort - simple!

Nearly all distillery have a Mash Tun, some like Glenfiddich have two, they are usually made of Cast Iron or Stainless Steel.

Photo: @WhiskynStuff

Cast Iron Mash Tuns in use at Bowmore (with in-laid wood features!), Caol Ila and Glen Scotia:

Photo: myannoyingopinions.com

Photo: lenstalk.com

Stainless Steel Mash Tuns in use at Ben Nevis, Glenfarclas, Loch Lomond and Glenlivet:

Photo: @WhiskynStuff

I've not seen any research indicating that either stainless steel or cast iron make better wash but the stainless steel ones are easier to clean.

Some are open topped like these at Deanston and Bruichladdich:

Some distilleries have Copper Domes to aid heat insulation and save energy when heating the water.

Copper Dome in use at Bunnahabhain, Ardnahoe and Ardmore:

Photo: Jassy-50

Some Mash Tuns are huge:

Photo : David Brodie

Bunnahabhain's, for example, is so large the 12.5 tonnes of grist receives four waters, the first two 50,000 litres at 64º C and 25,000 litres 80º C, the last two 21,000 litres and 20,000 litres at 90º C. The first two waters produce a total wort of around 66,500 litres going to the washbacks, while the last two are recycled into the first water of the next mash cycle.

Some are relatively modest:

Glen Scotia's, for example, is a 2.8 tonne Mash Tun, utilising three washes - 10,000 litres, 7,000 litres and 7,000 litres at increasing temperatures for a total wort of around 14,500 litres

But some of them, like at Edradour, Clydeside and Rassay, are quite small:

Photo: @WhiskynStuff

Photo: @JW_Bassman

Rassay Mash Tun on the left

Rassay's, for example, is a one tonne Mash Tun, utilising three washes - 3,500 litres, 2,000 litres and 3,500 litres at increasing temperatures for a total wort of around 5,000 litres

The Mashing Process

The Mashing process is all about the conversion of starch in the grist (crushed barley) into fermentable sugars by the addition of hot water. This typically takes 6 to 8 hours. The sweet liquid (wort) is then separated from the solids (draff) and, after cooling, pumped into washbacks for fermentation.

Photo: Glen Scotia

During each stage of the process the grist is agitated to separate the wort from the grain bed (the husks), either by hand, by a traditional rake, or by a series of bladed rods projecting down from a rotating arm.

By hand

The most traditional method, using a wooden rouser, still used at Glenturret:

Photo: Rob McDougall

Rakes

The traditional mash tun had a rotating arm in the middle, equipped with rakes of comb-like teeth that stir up the grain in the bottom of the tun to help extract the sugars and make it easier to drain the waters. A rake is generally used a couple of times when each batch of water is added, not continuously through the process.

Rake Mash Tun in use at Bunnahabhain, Edradour, Glen Scotia and Bruichladdich:

Photo: David Brodie

Semi-lauter

Spanning the width of the mash tun is a device with long vertical iron knives, themselves equipped with small fins, which are rotated around the mash tun by a spindle in the middle, again this helps to  extract the sugars and improve drainage. The name comes from the German to filter, "lautern"

Semi-lauter Mash Tun in use at Tomintoul and Arran:

Photo: Tomintoul

Full lauter

The Full lauter mash tun is very similar to the semi-lauter above, but here, the knives don’t just rotate, but can also move up and down in order to further stir the mix.

Full-lauter Mash Tun at Ben Nevis:

Photo: whisky.com

To stir or not to stir?

A lauter gives the option of continual gentle stirring - at Glenmorangie a single rotation, on the slowest speed setting, takes around 14 minutes - it's a balance between ending up with a clear or cloudy wort.

Underbacks

Most distilleries incorporate an Underback in their Mash Tun 'system', a tank connected to the bottom of the Mash Tun. After the first water the wash is transferred to an Underback, the second hotter wash then dissolves any remaining sugars in the grist and is added to the Underback. The wort is held here and suspended particles are allowed to drop out, resulting in a clearer wort.

Another process used to help create a clearer wort is in use at Lindores Abbey, the use of "vorlauf pipework", from the German “forerun“ and  coming from the German brewing industry is explained by Gary Haggart the Distillery Manager:

"Before sending the wort to the washback, what we do is firstly recycle it back into the top of the mash tun, these first waters contain solids which makes the wort cloudy, these solids once they go into the wash still will lean towards a nutty spirit, so by recycling these first waters, normally about 20 mins, we start to see in the return sight glass that the wort is clear, with this we change the direction of the wort and send it to the washback, clear wort is a good way to get a fruity style spirit"

Underbacks in use at Glenmorangie, Glen Scotia, Lindores Abbey and Arran:

Photo: Annie Hayes

Arran's Underback in action.

The final charge of hot water usually at around 85°C is added to the mash tun to dissolve anything worthwhile still left in the residue. This water, known as the "sparge", is drained off and used as the first charge of water to be added to the next batch of grist.

Wort Coolers

The wort is then transferred  through a wort cooler or heat exchanger, reducing the temperature to around 22°C to ensure it doesn't kill the yeast, to the washbacks. The recovered heat can be used to heat other  water for future mashes.

Dallas Dhu Wort Cooler - Photo: @WhiskynStuff

Photo: @JW_Bassman

Edradour use a Morton Refrigerator and cold water to cool their wort, this is the last of its kind still working in the whisky industry.

Photo: Edradour

Mash Filters

Some distilleries don't use Mash Tuns at all, their mash is instead fed into a Mash Filter to produce their wort. Teaninich and InchDairnie are amongst the pioneers of this process.

Teaninich Mash Filter

Normally the Mashing process takes place in a single vessel, the mash tun, but with a Mash Filter the process is split into two parts: conversion takes place in one tank then filtration and separation of liquid and solids takes place in the Mash Filter.

As explained in the Malt Mill blog here, a Mash Filter doesn't need the 70:20:10 ratio of grits, husks and flour, instead using 100% fine flour. the husks aren't needed as a filter bed.

The flour is hydrated with water either in a vertical hydrator (InchDairnie) where the hot water forms a vertex and the grist is drawn into it and it gets very wet or a steel tank Mechmasher (Teaninich). The wet mash falls into a Mash Conversion Vessel (MCV). This has a low sheer mixer in the bottom to keep it all moving without making it viscus. The vessel has a steam jacket around it and is heated up the to 64°C for around 3/4 hour and then onto 68°C.

InchDairnie Mash Filter

The hot mash is then pumped into the mash filter, which consists of a number of mesh bags – a bit like teabags, according to InchDairnie MD Ian Palmer. As the filter is filling up the clear wort runs through the filter. When the filter is full it closes up and the filter plates are compressed to squeeze out the wort. 

When it's empty the filter is filled again with 80°C hot water, the sparge, this washes the remaining wort out of the draff. Some of the last running’s of this wort is collected in the weak wort tank for use in the following mash. When the last of the sparge is in the plate are squeezed again to dry out the draff and collect the final weak wort which is reused for the next mash.

Waterford's Mash Filter

The mash filter approach results in the extraction of large amount of starch and sugar, which, along with carefully selected yeast strains, leads to more alcohol being produced during fermentation – the wash is pumped to the still at about 10% ABV, higher than the usual 6-8% found in other distilleries using Mash Tuns – and a higher overall alcohol yield after distillation. .The advantage of the mash filter is the production of very clear wort (which in turn can help to make a spirit low in or free of cereal notes).

The system can easily process ‘challenging’ malt – or other cereal grains, including rye – which conventional milling and mashing systems may struggle with.

Manufacturers

Briggs of Burton

Briggs can trace its history back to 1732 when Thomas Thornewill set up his company in Burton-on-Trent manufacturing metal hardware and industrial metalwork such as hoop iron for the local breweries. In 1865 Samuel Briggs sets up S. Briggs, in the same town, as an ironmonger and coppersmith again supplying to the local brewing industry. S. Briggs bought out Thomas Thornewill in 1929 and acquired Richard Sizer of "Porteus Mill" fame in 1993. They manufactured the Mash Tuns in use at Loch Lomond, Glenlivet, Cooley (Ireland) and others.

Newmill Engineering of Elgin (closed and taken over by William Reid (Engineering) Ltd)

A foundry in Elgin, founded in the early 19th century by James Johnston, manufacturing distillery equipment including the Mash Tuns at Speyside, Ben Nevis and Glenlossie, among others

Steinecker (now part of the Krones Group)

Dating back to the 1870's Steinecker is a German company specialising in brewing and distilling equipment. They manufactured the Mash Tuns in use at Craigellachie, Aberlour, Glen Elgin and others.

Forsyths

Founded in 1933 when Alexander Forsyth bought the brass and copperworks business of the retiring Robert Willison, he founded it in the late 1800's. Now run by the fourth generation of the family. Up until the 1980’s the majority of Forsyths revenue was generated from the whisky industry producing copper pot stills and condensers. A slump in whisky production at this time meant that work was scarce and Forsyths had to diversify in order to stay in business. The company developed its experience in carbon and stainless steels to enter the then busy paper industry. A natural progression from this led us into the oil and gas and pharmaceutical industries. As the company has grown it has broadened its experience into exotic metals like titanium and super duplex. They manufactured the Mash Tuns in use at Glenfiddich, Ballindalloch, Lindores Abbey, St George’s (England), Chichibu (Japan) and others.

Northern Fabricators (now part of Forsyths)

Northern Fabricators are stainless steel fabricators, coppersmiths, pipe-fitters, and maintenance engineers, founded in 1986 in Elgin, manufacturing distillery equipment including washbacks, pot stills and associated equipment. In 2012 they became part of Forsyths Group. They manufactured the Mash Tuns in use at Ardbeg, Ardnamurchan, Hven (Sweden), King Car (Taiwan) and others

Spectac International

Established in 1986, Spectac International is a significant manufacturer of Stainless Steel products, including vessels, tanks and related products for the Food and Beverages, Pharmaceutical, Chemical, Brewing, Distilling and Dairy industries. They manufactured the Mash Tuns in use at Teeling (Ireland) and others.

LH Stainless

LH Stainless is based in the North East of Scotland where they deign and manufacture for the distilling, brewing and offshore industries. They manufactured the Mash Tuns in use at Ardnahoe, Rassay and others.

Meura (now part of the French Boccard Group)

A Belgium company founded in 1845 by Jean-Baptiste Meura specialising in brewing equipment. They invented the first filter press to improve the mash lautering process in 1901 which lead to the development of their Mash Filter machines. The Meura 2001 was launched in 1987 with nearly 500 units in use around the world including at InchDairnie, Teaninich, Waterford (Ireland) and others.

Next Step

The Wash is then sent to the Washback, the Mash Tun then needs to be emptied of the spent grist - this usually goes to animal feed. At Glenturret it's all done by hand:

Photo: Rob McDougall

Geeky Stuff:

Some Mash Tun examples:

Distillery	Type	Size (Tonnes)	Stirring
Edradour	Iron	1	Rake & plough
Wolfburn	Steel	1	Semi-lauter
Glenturret	Steel	1	By hand
Raasay	Steel	1	Semi-lauter
Glen Scotia	Iron	2.8	Rake & plough
Ardbeg	Iron	4.5	Semi-lauter
Bruichladdich	Iron	6.5	Rake & plough
Ben Nevis	Steel	8.5	Full-lauter
Glenfiddich	Steel	9.5	Semi-lauter
Tomintoul	Steel	11.5	Semi-lauter
Bunnahabhain	Steel	12.5	Rake & plough
Glenlivet	Steel	13	Full-lauter
Caol Ila	Iron	13	Full-lauter
Macallan	Steel	17	Full-lauter