In the Tun Room, the sugar solution (wort) is fermented by yeast into a weak alcohol solution called ‘WASH’. The vessels in the Tun Room are called ‘Washbacks’. The North British has 24 washbacks, each with a capacity of 200,000 litres and 14 washbacks of 400,000 litres capacity. The total capacity of the Tun Room is approximately 10 million litres.
Each washback has to be sterilised before it is used. Spraying the inside of the vessel with hot caustic soda does this. Fermentation lasts for at least 72 hours, and at the end of that time, the alcohol concentration in the wash is about 8%.
Carbon Dioxide gas (CO2) produced during fermentation is routed to the CO2 recovery plant for processing.
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