What on earth is a Wormtub?

Every step in the complex process of distillation has an effect on the spirit and the resulting whisky made at each distillery. Some of these processes and their effects are obvious, such as the use of peated barley or different cask types for maturation. There are also a number of processes whose influence tends to go unnoticed, and one of those is how the spirit is condensed during distillation.



Inside a copper pot still, its contents are heated to a temperature where the alcohol vapourises and then rises like steam, heading towards the top of the still where the lyne arm connects the still to the condenser. 



Traditionally, condensers are made from a tapered coil of copper, referred to as a worm, submerged in a large vat of water outside the distillery. In the naturally temperate conditions of Scotland, worm tubs provide a slow and gentle condensation as the hot vapour meets the cool copper. 


This system was used from the earliest days of illicit whisky making through to large-scale commercial distilling in the 1800’s up until the 1950’s and ’60’s when the far more efficient and cost-effective shell-and-tube condensers saw widespread use. Forgoing the large worm and vat, these new condensers consist of dozens of narrow copper tubes, packed together like a bundle of straws and surrounded by a jacket (shell) that contains running water, creating a large surface area of cool copper that the vapour rapidly condenses in.



The major difference between these two methods is in their efficiency of removing or reducing the concentration of certain organic compounds that occur in the spirit. The reduced efficiency in wormtub condensers results in a heavier profile in the spirit that creates a complexity and character during maturation that is highly desirable to some styles of whisky.



Today, there are just a small handful of distilleries that stick to using worm tubs, and they would argue that it is an essential part of the flavour of their whiskies. Mortlach, Dalwhinnie, Benrinnes and Craigellachie are among the most well-known old distilleries still using this equipment, but it has also found favour with a number of new distilleries like Ardnahoe (pictured above) and Ballindalloch who are preserving this traditional method.