The stills tend to work in pairs. Firstly, the wash enters the larger wash still and is heated (this was traditionally by coal, but is now largely by gas or steam). 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 a stillman and collected through the spirit safe. 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.