After fermentation comes distillation. We distil twice in order to reach the required strength and desired pure spirit. The first distillation happens in the wash still. It is filled with fermented wash, boiled until the alcohol vapours start rising up the neck of the wash still, pass through the Lyne Arm and finally reach the Condenser, where they are condensed back into liquid form.
The liquid spirit then flows through the spirit safe and travels into the low wines and feints receiver. Any spirit still being produced through the wash still is called low wines. At this stage the alcohol content of the spirit is about 24% alcohol.
HERE COMES THE SCIENCE BIT
The next distillation is done in the spirit still. The same boiling and condensing process applies but the major difference is that the strength of the spirit has increased to 76% alcohol and the quality of the spirit has improved dramatically. However, because there is still an element of impurity in the spirit, we run the initial 10 minutes of spirit back to where it came from (the low wines and feints receiver).
This 10 minutes of spirit is called foreshots. After 10 minutes the spirit is of the highest quality. The spirit is then diverted into a vessel called an intermediate spirit receiver. This is the start of the Spirit Cut i.e. the spirit which will eventually be filled into casks. We run on spirit for around 4.5 hours until the strength is about 62.5% alcohol. At this strength the alcohol is beginning to show off notes i.e. impurities so we divert it back to the low wines and feints receiver for further distillation. So try and picture low wines going into the receiver from the wash still at the same time feints are entering the receiver from the spirit still.
SWEETNESS, FRUITINESS AND FRAGRANCE
During distillation the alcohol vapours evaporate quicker than water so the whole theory of distillation is to try and leave as much water behind as we possibly can, thereby increasing the strength of the spirit. As low wines and feints are nearing the end of their runs i.e. down to 1% alcohol, we stop boiling because we are basically boiling water (the other 99%).
On the Lyne arm of the spirit still at Ardbeg there is a piece of apparatus called a purifier. As the boiling continues in the spirit still, the heavier impure alcohols reach the top of the still (the initial light alcohols are sweet and fruity). Some of the heavier compounds are captured in the purifier and fed back down into the main pot of the still. As the boiling process continues, the heavier phenolics come through, this occurs from about halfway through the spirit run. The purifier gives a little extra reflux, so we have two distillations and a little bit more.
The lighter alcohols are collected during the first two hours of the spirit run. Some heavier alcohols include the phenolics, and those are collected during the second half of the spirit run. This is what gives Ardbeg its great balance and complexity because the heavy peat notes never at any time dominate, although we are using very heavily peated malt. The purifier is unique on Islay and balance is the key.