Worm-Tubs

What are distillery worms and worm-tubs? Do they affect flavour?

They sound like a species of earth-worm, kept in tubs to effect some magical transformation of the spirit!

In fact they are a type of condenser which was once universally used by whisky distillers, comprising a serpentine copper tube of decreasing diameter, attached to the head of the pot still, via the lyne arm or lye pipe, and placed within a large tank of cold water – the worm-tub. Alcohol vapour enters to top of the worm and condenses as it travels down, to be received as liquid at the bottom.

In regard to flavour, the vapour/spirit has much less contact with copper on its journey than it has in the familiar shell-and-tube condensers now used by most distilleries, and as a result tends to be heavier in character, more robust and some would say ‘more traditional’, especially if the water in the tub is very cold. If the water is held back to become warm, or even hot, the spirit stays as vapour longer and interacts more with the ‘purifying’ copper.

I know of only eighteen distilleries which currentl have worm-tubs. They are: Ballindalloch, Balmenach, Cragganmore, Craigellachie, Dallas Dhu (currently a museum with plans to reopen), Dalwhinnie, Edradour, Glen Elgin, Glenkinchie, Mortlach, Oban, Pulteney, Rosebank, Royal Lochnagar, Speyburn, Springbank (wash still only) and Talisker.

Dalwhinnie’s worms were replaced by shell-and-tube condensers in1985, but the spirit was so different they were reinstated in 1996 – clear evidence of the impact worm-tubs have on spirit character!

Worms were (almost) universal until the 1960s and 1970s, when they were replaced by ‘shell-and-tube condensers’ - tall cannisters filled with dozens, sometimes hundreds, of copper tubes surrounded by cold water. The alcohol vapour passes down the tubes and condenses en route, with much more contact with copper, making for a lighter and fruitier style of spirit.

Not only was this style of whisky more popular with blenders (the distillers’ key customers), the condensers were more efficient and economical - faster, capable of handling larger still charges (so increasing production capacity), less cooling water required (greater energy efficiency), easier to maintain and control, and making for more uniform condensations.

Their use (or part use) had been explored in the 19th century, by Hazelburn Distillery in Campbeltown (1837) and Nevis Distillery, Fort William (1878), and significantly these condensers were installed by Glenmorangie Distillery when it was rebuilt in 1886/87, to work alongside its massively tall stills, indirect fired by steam in internal pans and coils. All of these innovations increased copper contact, making for lighter spirit.

In his seminal The Whisky Distilleries of the United Kingdom (1889) Alfred Barnard mentions only three malt distilleries (apart from Glenmorangie) which had condensers – Glenugie, Dean/Edinburgh and Bowmore (which used them in parallel with worm-tubs) – and two grain distilleries: Cameronbridge and Kirkliston.

In spite of the advantages they offered, shell-and-tube condensers were not embraced by the traditional and conservative Scotch whisky industry until the 1960s and ‘70s, when the demand for Scotch required increased efficiency in production.

The first was Macduff Distillery (built 1962-63) and designed by the leading distillery designer of the day, William Delme Evans, and this was followed by all new distilleries and almost all distilleries which were being expanded and modernised - which was most of the existing malt distilleries - during in the 1960s and 1970s.

It is interesting that of the six distilleries United Distillers (now Diageo) chose to represent regional differences in its Classic Malts Collection (1988), five have worm tubs: Glenkinchie, Oban, Dalwhinnie, Cragganmore and Talisker. Clearly worms promote flavour/texture!