8 • THE KNOWLEDGE The quest for whisky enlightenment continues THE INSIDE
THAT COUNTS IT’S WHAT’S ON
This issue, we lift the lid on a still and look at copper’s role in whisky-making WORDS: GARY ATKINSON
When the early distillers began to replace glass and ceramic stills with copper versions (mainly because copper is much easier to bash into shape), it proved to be serendipitous as, along with water, barley, yeast and wood, copper plays a significant role in shaping the flavour of whisky
Copper’s role Copper acts as a purifier, suppressing the compounds responsible for sulphury and meaty aromas, thus producing a lighter spirit. One such compound is dimethyl trisulphide, which smells like rotting vegetables – even very small amounts can have a big influence on the spirit. Professor Paul Hughes,
Director of the International Centre for Brewing and Distilling at Heriot-Watt University, explained: “When the liquid comes in contact with the copper in the still and condenser, the copper combines with some of the sulphurous compounds, neutralising their flavour and aroma, to create an extremely insoluble material. “These solids are left behind in the stills and waste by-products. However, low levels of copper do make it into the final spirit.”
Condenser choice is crucial It is in the wash still’s
THE SCOTCH MALT WHISKY SOCIETY
condenser where a lot of the copper and sulphur reaction takes place – this is where the spirit vapour is condensed into liquid form. The choice of condenser has an impact on the amount of sulphur in the final product. A worm tub comprises a coil of copper tubing, through which the vapour from the still passes, immersed in a tub of cold water. A more modern version is
the shell and tube condenser, made completely from copper, where cold water flows through a number of copper tubes, all housed within a larger tube where the vapour flows. Because there is a greater surface area of copper within the shell and tube condenser, more sulphur is typically taken out of the spirit than compared with a worm tub.
Sacrificing the metal With the wash being slightly acidic, this accelerates the rates of copper reactions with sulphur compounds. But a greater reaction also means greater erosion of the copper. Richard Forsyth of still
makers Forsyths said: “In the two-part distillation process for whisky, it is in the first part – in the wash still – that the sulphur in the vapour is particularly harsh on the condenser, the lyne arm and the swan neck, which all need to be
replaced within 8-10 years. “In the second part – in the spirit still – the opposite is true, it is the pot that needs replaced after that period. The entire still and condenser apparatus will need completely replaced typically every 25 to 30 years.” Richard continued:
“Typically, a pot still and condenser will weigh between four and five tonnes. In a pot’s lifetime, it will lose about half of its weight due to erosion.”
In with the new Every year, distilleries check the thickness of the copper in their stills and condensers. Tapping a hammer against the metal and listening to the noise was the traditional way of assessing thickness, but today, ultrasound technology is used. When a replacement is needed, it will be forged from a wide range of sources. Richard explained: “About
70 per cent of the copper to make our stills and condensers comes from recycled copper, such as from old pipes, electrical wires and even old stills. The remaining 30 per cent comes from ore, mined from places in South America, such as Chile and Mexico, and also South Africa.”
From the glass to the body Copper is actually essential for human health; it helps produce red and white blood cells and triggers
the release of iron to form haemoglobin, which carries oxygen around the body. The recommended daily intake is 1.2 milligrams a day for adults. A dram of whisky, however,
typically contains just a miniscule 25 micrograms, according to Professor Hughes. He added: “If you were to try and get your daily copper allowance from whisky alone, then you will have greater problems than a copper deficiency!” A varied and healthy
diet, particularly of copper- rich foods such as shellfish and nuts, will give you all the copper you need.
Is there an alternative? If whisky makers were feeling particularly flush, there is another metal that could take the place of copper. Professor Hughes explained:
“Technically, you could use gold stills for whisky distilling. It has a lot of the same properties as copper. For example, it could take out sulphur compounds, but perhaps not at the same level of copper, which is a more reactive metal generally. It is also an excellent conductor of heat, and as the most malleable metal, it can be easily shaped. The cost, however, would obviously be an issue!”
PHOTOGRAPHY: MIKE WILKINSON
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