The cooled worts are
injected with yeast and the fermented in a further tank or tanks called
'washbacks'. Thirty-six hours or thereabouts of sometimes violent fermentation
produces a weakly alcoholic (10° or thereabouts) clear liquid called
'wash', which will now be distilled.
Fermentation can be extremely vigourous, producing a 'head' several feet deep.
Washbacks are often mechanically agitated to knock back the head or it would
The wash is allowed to ferment to a beer-like liquid containing about 5%