Whisky 'machinery' - the Washback

Continuing the series looking at some of the 'machinery' used in a distillery to create whisky - this time the Washback or fermenting vessel.

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 wash has been created in the Mash Tun it's filled into a Washback, yeast is added, fermentation occurs, creating beer - simple!

Probably the simplest of the whisky 'machinery' I've talked about so far is the the Washback - it's basically a large vessel where yeast is added to the wash, fermenting the dissolved sugars into alcohol.

Washbacks are usually sized to match the size of the Mash Tun, so one run of mash will fill one Washback. The Washbacks aren't filled to the top as space needs to be left for the yeast to grow during fermentation. A lot of carbon dioxide is created during this stage, and the foam generated during the process could easily over flow the washback. To prevent this from happening, some distilleries implement a device called a switcher blade (rotating blades), which will remove the generated foam. 

Washbacks are usually made of one of two materials - traditionally wood or more recently stainless steel. Some distilleries use both, again like a Mash Tun, a stainless steel one is easier to clean, it doesn't have the little nooks and crannies of a wooden vessel.

Wood

Most distilleries use Oregon Pine (also known as Douglas Fir, Douglas Spruce and Columbian Pine) or Larch but other wood could be used as long as it is long, straight and has a tight structure that’s impervious to leaks. Larch has a tight grain and smooth surface, whereas Douglas Fir has a slightly more open grain and rougher surface. Japanese distillery Chichibu have Mizunara Oak Washbacks.

Like a cask or barrel a Washback is usually held together by up to 16 steel bands. Wooden washbacks have an average life-cycle of around 30 years - leaks, rust build-up behind the steel bands, soft rotten timber, and woodworm need to be watched for.

There is very little influence of the wood on the wash as the liquid is only held there for a such a short time typically 50-150 hours.

Joseph Brown Vats of Dufftown is one of the key specialists in the building, supply and installation of  Douglas Fir washbacks.

Steel

The first use of Stainless Steel washbacks in Scotland was in 1949 at Tullibardine.

Richard Forsyth of Forsyth’s is one of the key suppliers of stainless steel washbacks.

Cast iron

During the 19th and 20th century,  distilleries looked for alternatives to the wood, primarily due to the additional cleaning, but also because wood has a limited lifespan. Their solutions at the time was to use cast iron or corten steel. Ben Wyvis and Allt-A-Bhainne amongst others used to have cast iron washbacks, Glen Scotia used Corten Steel until 2012

Glen Scotia's old Corton Steel Washbacks

Photo: Steffen Bräuner

The old washbacks being removed and replaced with Stainless Steel ones!

Glen Scotia Corten Steel Washbacks c1980

Ben Wyvis Cast Iron washbacks - Photo: J R Hume

Allt-A-Bhainne's old Cast Iron washbacks - now replaced by Stainless Steel.- Photo: whisky.com

Concrete

Ben Nevis distillery had concrete washbacks installed by the then owner Joseph Hobbs in the 1950s, but these were replaced, in 1989 when Nikka bought the distillery, with two wooden and six steel washbacks.

The now closed Japanese Karuizawa distillery also used epoxy-lined concrete washbacks - they were replaced in 1991.

Washback Sizes

As you will see from some of the pictures below Washbacks are probably the biggest vessels in a distillery, here's some example sizes:

Distillery	Material	Capacity (litres)	Height	Diameter
Tomintoul	Steel	80,000	4.45m	4.79m
GlenAllachie	Steel	56,500	4.5m	4m
Bruichladdich	Wood	40,000	5.5m	4.25m
Glenrothes	Steel	c30,000	3.5m	3.6m
	Wood	c30,000	3.8m	3.7m
Glen Scotia	Steel	25,000	4.7m	2.7m
Lindores Abbey	Wood	13,000	5m	4m
Port of Leith	Steel	7,100	4.2m	4m

Washback Variations

Springbank has a typical old school set up in their tun room, six Boat Skin Larch washbacks, each takes 21,000 litres of wort and 75g of yeast is added. Fermentation times are between 72 and 100 hours giving a wash of around 5% ABV

Bowmore six Oregon Pine Washbacks, 50  hours giving a wash of around 5% ABV

Photo: Thijs Klaverstijn

Bruichladdich have 6 Oregon Pine Washbacks, Each takes 35,000 litres of wort which is fermented for around 80 hours giving a wash of around 6% ABV

Bruichladdich replacing one of their wooden washbacks in 2013

Edradour have two Oregon Pine Washbacks.

Photo: Kravitz Hubris

Glen Scotia now have six washbacks inside the distillery and three outside. Each takes 15,500 litres of wort and 75g of yeast is added. Fermentation times are between 70 and 140 hours giving a wash of around 8% ABV

The three outside Washbacks have a slower fermentation rate due to the lower temperatures, this gives a slightly different flavour profile - with stronger fruit notes in the raw spirit

Port of Leath distillery in build with it's two stainless steel washbacks in position.

Ardnahoe have four traditional Oregon Pine washbacks 

Loch Lomond have 41 Stainless Steel Washbacks, ten 25,000 litre inside & eleven 50,000 litre outside for the malt side of the distillery and twelve 100,000 litre inside & eight 200,000 litre outside for the grain side of the distillery. Now you might think that that is pretty big? Loch Lomond's grain distillery has a capacity of 20 million litres of alcohol per year. Compare this to giants Girvan and Cameronbridge who both produce over 120 million litres per year!

Malt distillery - ten 25,000 litre indoor washbacks - Photo: Michael Henry

Malt distillery - eleven 50,000 litre outdoor washbacks and you can just see some
of the eight 200,000 litre Grain ones in the centre of the picture - Photo: Michael Henry

Grain distillery - twelve 100,000 litre indoor washbacks - Photo: Michael Henry

View from the top of the outdoor Malt washbacks - Photo: Michael Henry

Control centre for the Grain distillery washbacks

GlenDronach have nine wooden washbacks, each with a capacity of 18,000 litres. The wort is fermented for between 60 and 96 hours.

Photo: Mark H. (Mark @ WTF)

GlenDronach building a Scottish Larch Washback in 2013 - Photo: Karen McWilliam

Glenrothes have 12 Oregon Pine and 8 stainless steel washbacks - with a 58 hour fermentation time.

Chichibu have eight Mizunara Oak Washbacks, each just over 3,000 litres, fermentation lasts up to 100 hours resulting in a wash of around 7 % ABV

Photo: Whisky Saga

Laphroaig have six stainless steel washbacks, fermentation times of around 55 hours give a wash of around 8.5% ABV

Glenfarclas went from Wood to Steel but kept the wooden tops, their twelve washbacks ferment for around 75 hours giving a wash of 8% ABV

Photo: @WhiskynStuff

Photo: @WhiskynStuff

Photo: @WhiskynStuff

Bimber distillery went the other way and replaced Steel ones with Wooden ones, uniquely theirs are open topped allowing wild yeast to join the party!

Three Stainless Steel 1,000 litre washbacks - Photo: Bimber

Seven American oak 2,000 litre washbacks - Photo: Bimber

Shapes

As you can see from all of the photos above, most washbacks are cylindrical in shape. Adnams are one of a few exceptions use rectangular ones! This is due to their use of top fermenting yeasts, which prefer shallower liquid depths, rather than standard bottom fermenting distillers yeast which can work with a greater depth of liquid.

Cleaning

After each use a washback, both steel and wood, needs to be cleaned - this is normally done using steam. Wood is porous and can allow a bacteria that thrives off the sugars in the wash to grow in the crevices of the washback, therefore they must be properly cleaned between uses. Stainless steel has a lower risk of bacteria growing but they must also be  cleaned thoroughly.

Photos: Lindores Abbey

Next Step

Once fermentation is complete the wash is transferred to a still for distillation...