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DISTILLATION


Distillation is the process used to increase the alcohol content from the 6-10% in the wash to the final 63% of cask strength Athrú whiskey. For this process we think of the wash as being a mixture of water and alcohol. We want to remove and collect the alcohol while leaving behind some of the water in order to make a more concentrated alcohol solution. Importantly, alcohol boils at 80°C but water boils at 100°C and we can use this property to separate them. The distillation process involves heating the mixture of two liquids with different boiling points (i.e. the wash containing alcohol and water) to a mid-point and the vapour given off is then cooled and collected. As the alcohol has a lower boiling point it will begin to evaporate first and will be present in higher percentage in the vapor and the resultant collected liquid. Irish whiskey has traditionally been distilled 3 times, which is why we have 3 pot stills. Scotch, on the other hand, has traditionally been distilled only twice. As the alcohol in the wash is separated from the water, increasing the alcohol content, there is obviously less and less liquid. So, the first pot still (called the wash still) holds 15,000 litres, but the second pot still (called the feint still) is only 12,000 litres and the third (called the spirit still) is only 7,500. Our pot stills are made by Frilli and are 100% copper with a stainless-steel bottom and the liquid is heated externally by heat exchangers to help with consistency. The process starts by filling the wash into the wash still. It is then heated, and the liquid starts to evaporate. This vapour moves up the neck of the pot still (called the swan neck) where it meets a bulge (called the boiling bowl). Here some of the liquid condenses and falls back into the pot still, in a process known as reflux. Eventually, however, it makes its way into the horizontal part of the pot still called the lyne arm and from there into the condenser. The condenser is filled with small bore tubes of cold running water. When the vapour hits these it condenses back into liquid to be collected in the tank below. On its way to the tank, it passes through the glass “spirit safe” which allows the distiller to monitor performance. It also, traditionally, allowed the Revenue to verify the operation of the distillery. The first distillation in the wash stills takes approximately 4 to 7 hours. The wash still has a temperature of approximately 78°C, the evaporation point of ethanol. With each distillation, the evaporating liquid is made up of heads, hearts and tails. The heads (or foreshots) contain compounds like Acetone which, chemically, is too harsh and smells bad. The tails (or faints) have a bitter taste and are also discarded. The hearts (or spirit) contain primarily ethanol and are rich in flavour, smell great and taste smooth. This is the liquid that will eventually end up as whiskey. In this first pot still an alcohol solution is produced with about 20 to 25 alcohol by volume (ABV). It is called the low wines. This is then filled into the feint still and the process repeated, this time producing an alcohol solution with about 30 to 35 ABV. It is called the feints. This is then filled into the spirit still and the process repeated a third time, producing a colourless spirit which has a high alcohol content of around 63% ABV. This will eventually become cask strength Athrú whiskey. Alcohol that undergoes triple distillation is lighter in colour while maintaining a higher strength of spirit, resulting in a cleaner, crisper taste.


 
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