Making whisky - from grain to pot still
How to Make Whisky
Take some roasted barley, add water and yeast, and let it bubble, and heat until it evaporates, collect the liquid and store in an oak barrel for several years. OK, obviously it is a little more complicated than this, but in essence that’s it.
The five main stages in the production of whisky:
- Milling or Grinding and Mashing
The whisky must be aged or matured in oak barrels for a minimum of 3 years.
The five stages explained and illustrated by video from the Glengoyne Distillery.
Raw Barley grain is steeped in water until it begins to germinate. It is then spread over the floor of the malting house and turned several times a day, originally by hand, but nowadays mostly by machine operated wooden paddles. The turning allows air to circulate around the barley, encouraging further development. After about two weeks the starch in the grain has turned to sugar and the germination is stopped using heat. Traditionally the heat came from peat fires which imparted a smoky aroma and flavour into the whisky. Islay whiskies are still famous for this peaty style.
Milling and Mashing
The barley is dried and ground in a mill producing a type of ‘coarse flour’ called grist.
The grist is next mixed with hot water to form ‘mash’ and poured into a ‘mash tun’, where it is stirred regularly. The result is a sugary liquid called ‘wort’. The remaining solids, ‘draff’ are used as cattle feed.
The wort is transferred to a ‘washback’ where yeast is added and the fermentation process that turns the sugar into alcohol begins. After 2 – 4 days the ‘wort’ will become ‘wash’, a type of beer, and about 8% abv.
The ‘wash’ is transferred into copper pot stills which are heated and cause the alcohol to evaporate and separate from the water content, achievable because the boiling point of alcohol is about 20 degrees lower than water.
The first distillation in the wash still, ‘pot still’, turns the wash into ‘low wines’ a liquid with an alcohol content of about 21%.
From the wash still the spirit passes through the spirit safe and then into the spirit still, where the second distillation occurs. The spirit then passes to the spirit safe, which is padlocked and under the control of Customs & Excise. Here it is tested with hydrometers and checked for purity.
Spirit Safe at Auchentoshan. Note the intermediate distillate, present because at Auchentoshan the spirit is triple distilled.
During the distillation process the stillman must separate the ‘middle cut’ from the foreshots or heads, which are too high in alcohol and the feints or tails, which are too low. The feints are returned to the stills and mixed with the next lot of wash to be redistilled.
The Spirit is diluted with demineralised water to strength of 63.5%. It is the stored in Oak casks in a bonded warehouse for a minimum of 3 years. In practice whisky is usually stored for much longer than this. The lengthy ageing process is an expensive one, with no financial return until the whisky is bottled, either as single malt, or blended with grain whisky.
The Oak casks will have had previous occupants, such as Port, Sherry, Medoc etc., and this affects both the colour and the flavour of the whisky.