Barley contains starch and it is this starch which needs to be converted into soluble sugars to make alcohol. For this to occur, the barley must undergo germination and this first part of the process is called ‘malting’. Quality Australian malted barley is sourced and milled to a suitable consistency.
The ground down malt, which is called ‘grist’, is now added to warm water to begin the extraction of the soluble sugars. The liquid combination of malt and water is called the ‘mash’. It is put into a large vessel called a mash tun and stirred for several hours. During this process, the sugars in the malt dissolve and these are drawn off through the bottom of the mash tun. The resulting liquid is called ‘wort’. This process is normally carried out three times with the water temperature being increased each time to extract the maximum amount of sugar. Only wort from the first two times is used. The third lot is put back into the next batch of new grist. Any residue, such as husks, is called ‘draff’. This is collected and used in the production of farm feed.
The wort is cooled and passed into large tanks called washbacks. Here the yeast is added and the fermentation begins. The yeast turns the sugars that are present into alcohol. The fermentation normally takes around 48 hours to run its natural course, The liquid at this stage is called ‘wash’ and is low in alcohol strength (between 5-10% ABV), like beer or ale. You could make beer from the liquid at this point, but the difference with whisky is that the liquid is now distilled rather than brewed.
The stills are made from copper, which has been found to be the best material for extracting impurities from the spirit as it is being distilled, and consist of a bowl shape at the bottom that rises up to the neck at the top. Taller stills with longer necks will give finer, lighter spirits while shorter, fatter stills will produce a fuller, richer spirit.
The stills tend to work in pairs. Firstly, the wash enters the larger wash still and is heated. The liquid vaporises and rises up the still until it reaches the neck, where it condenses. This liquid is called ‘low wines’ and is unusable as it is.
The low wines are passed to the second smaller still, called the spirit still. Any residue from the wash still is collected and used to manufacture farm feed. In the spirit still, the alcohol produced is split into three.
Alcohols from the beginning of the distillation (called ‘foreshots’) are very high in alcohol level and very pungent. Alcohols from the end (called ‘feints’) are weak but also pungent. It is only the alcohol from the middle or ‘heart’ of the distillation that is used and this is skillfully removed by the distiller. The foreshots and feints are then mixed with the next batch of low wines and re-distilled. The heart is the spirit that is then taken to be matured and that will become whisky. This ‘heart’ has an alcoholic strength of 65-70% ABV.
The spirit is put into oak casks and stored. The most common types of oak casks are those that have previously been used in the American bourbon and Spanish sherry industries. The spirit must mature in casks for a minimum of two years before it is legally allowed to be called whisky in Australia. During maturation, the flavours of the spirit combine with natural compounds in the wood cask and this gives the whisky its own characteristic flavour and aroma.