The stink about sulphur

“The greatest trick the devil ever pulled was convincing the world he didn’t exist.”
The Usual Suspects, 1995

Substitute “whisky industry” for devil and “sulphur” for he and you’ll get a quick snapshot of what’s being discussed here.  Sulphur is one of the more confusing and least understood aspects in today’s whisky community.  Let’s cut through the taint and kill a few myths and misunderstandings…

Sulphur (as an element and in compound form) is present in whisky due to two sources.  One is natural, desirable, and is present in every malt whisky; the other is an accident, pretty much undesirable, and occurs only in some sherried whiskies.  The former is complex and actually difficult to discern; the latter is simple and sticks out like the Macallan distillery’s refurbishment budget.

Let’s consider the first source first: Sulphur is an innocent, naturally occurring and present element in whisky through the production process, with sulphides being a by-product of fermentation.  How much is present in the final spirit put into cask is dependent on several factors, although it’s chiefly due to the amount of contact the spirit has with copper.  Copper effectively strips the sulphur from the spirit (forming copper sulphates), and so the more contact the spirit has with copper, the less sulphury the spirit will be.  We discern this sulphur by certain flavours and aromas that typically get described as meatiness, savouriness, or being meaty.  (Think roast beef, Bonox, beef stock, Bovril, vegemite, and the like.  To be clear, you won’t hear this type of sulphur described as cabbage water, burning rubber, brimstone, gunpowder, cordite, or rotten eggs.)

The amount of contact the spirit has with copper during production is controlled or influenced by the still and its condenser.  The copper contact in the still comes about due to (1) The shape and size of the still relative to its volume; (2) the amount of reflux during distillation (i.e. how much the spirit condenses whilst rising up the neck and falls back down into the still again); and (3) the shape, size, and level of inclination of the still’s neck and lyne arm.  Once the vapours finally clear the lyne arm, the condenser then plays a role:  Modern “shell and tube” jacket condensers promote greater copper contact and thus more sulphur is stripped out.  In contrast, old, traditional “worm tubs” result in less copper contact and thus produce a more sulphury (meaty) spirit.  Examples of the latter – which remain in place at only 13 of the “old” distilleries – include Talisker, Mortlach, and Craigellachie.  Some of the recently established new distilleries are also opting for traditional wormtub condensors – Ballindalloch being a good example.

The secret inside a wormtub – new copper coils being installed at Talisker.

The second source of sulphur in whisky is the contentious one and can be present only in whiskies with sherry cask maturation.  When the sherry casks sat empty waiting for transport from Spain to Scotland, it was not uncommon to sterilise the casks by burning a sulphur candle inside the cask.  Whilst this killed off all the bacteria and micro-organisms that might ruin a maturing spirit, it had the unintended (unforeseen?) result of inflicting odorous sulphury notes in the resulting whisky.  Precisely when this practice started (and whether or not it has entirely stopped) is an argued point in the industry, although the 1980’s and 1990’s appear to be the main troublesome years.  Some attribute the practice to have become significantly more widespread in the 1990’s when new laws introduced in Spain meant sherry could only be exported in bottles – putting an end to the bulk transport of sherry to the UK in the sherry butts themselves.  This resulted in casks sitting empty for extended periods in Spain before being despatched to Scotland and thus requiring some form of treatment to prevent bacterial contamination.

The big problem is that, once the sulphur is there, it is there for good. With casks being re-used up to three and occasionally four times, the “infected” casks will continue to impart sulphur influence for decades to come.  This is the sulphur taint that results in tasting note descriptions such as cabbage water, cordite, rotten eggs, rubber, etc).   Some commentators, particularly Jim Murray, have been vocally scathing and vitriolic towards the practice and the outcome; others seem to prefer that the problem doesn’t exist or that the resulting aromas and flavours are merely just another shade on whisky’s complex spectrum.  Saddest of all is the generation of whisky drinkers who now assume or believe that sulphury whisky is synonymous with sherry wood maturation.

How many sherry butts in a typical warehouse are tainted by sulphur?

The unfortunate reality is that everyone’s sensitivity to this sulphur is varied.   And this is where the arguments start.  When it comes to sulphured whiskies, some folks have a genetic blind spot and won’t/can’t notice it.  Other drinkers simply don’t mind it or are happy to tolerate it.  Some believe or fall for the spin doctoring of the brand ambassadors who insist it is an acceptable part of the whisky making process or even just part and parcel of sherry maturation.   And others – including yours truly – are repulsed by it and can occasionally find the offending whisky near un-drinkable.   It thus becomes a difficult tasting descriptor to be objective about.  How can one person condemn and dismiss a dram for an aroma and flavour profile that some drinkers won’t even detect?

Whether you like sulphur-taint from the cask; merely tolerate it; or find it horrid; make no mistake:  It’s not meant to be there.  It is a defect and flaw in maturation.  It’s an outcome that wasn’t meant to occur.   And it’s something that wasn’t overtly in sherried whiskies up until a few decades ago.  Like everything else in whisky, a point of reference goes a long way:  Find yourself a clean and untainted sherried dram, and you’ll suddenly discover why so many “old school” whisky enthusiasts pine for the days when you could buy a sherried whisky with confidence, knowing you were getting a clean, uncontaminated parcel of joy in a bottle.

The problem is obviously significant for the distilleries that focus on sherry maturation – Glenfarclas and Macallan being the two biggest victims and having to deal with it accordingly.  (That’s not to imply all releases by either distillery have sulphur taint – merely that their respective cask inventories need to cope with the bad eggs).  Vatting the tainted casks with clean casks into a mass-produced 12yo expression (for example) at 40% ABV allows the sulphur influence to at least be dulled or diminished down to vaguely tolerable levels.  But the overall flavour profile and quality of the expression will clearly be different to how that same expression may have been perceived twenty years ago.  (Adding fuel to the argument that whisky today is not as good as it used to be in decades past).    Alternatively, some tainted casks find their way into the hands of independent bottlers who then bottle them as single casks in all their naked, sulphured glory.  All the mainstream IB’s have been guilty – Adelphi, Signatory, Gordon & MacPhail, Duncan Taylor, Douglas Laing, even the SMWS.

So, looking for a positive outcome, or simply just to end on a high note, is there anything good that sulphur-tainted casks have done for the industry?  Aye, indeed:  They’ve given us a more pronounced and direct appreciation for sherried whisky that is “clean”.   Just don’t fall for the devil.


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Author: AD

I'm a whisky host, writer, presenter, educator, taster, critic & all-round malt tragic! Also Director & Cellarmaster of the Scotch Malt Whisky Society in Australia. Follow me on Twitter and Instagram @whiskyandwisdom and also on Twitter @SMWS_Australia

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