Single casks are the rarest bottlings by definition. In the whisky industry, standard official bottlings of any given single malt whisky may be the product of hundreds of casks and come in batches of tens of thousands of bottles. By contrast, a single cask of whisky is painfully finite: the Scotch Whisky Regulations dictate that whisky must be aged in casks with a capacity of less than 700 litres, and in practice most of the larger casks used to mature whisky are sherry butts, which rarely exceed 550 litres. 

The vast majority of casks used to age spirits are hogsheads, which are around half that size - and that’s before the angels have had their share. It’s therefore not uncommon for long-aged whiskies and rums to yield fewer than 100 bottles from a single hogshead cask. At the other end of the scale are those bottlings where two smaller casks are reracked into a larger cask for finishing. These editions are bottled from a single cask even if they started out in two separate casks, so we've included them in this section too.

The good news is that tasting single casks remains one of the greatest pleasures available to spirits fans, with an almost unlimited potential for discovery.

Single casks show us the extraordinary array of subtle character variations that spirits possess. No two casks can ever be the same, so whether it’s whisky, rum, cognac, armagnac, tequila or any other aged spirit, single casks show us a profile of that particular liquid’s history from still to glass: a vertical snapshot of the period that this spirit has rested and matured in oak.

Tasting single casks, particularly for whisky, gives us insights into what may have been previously unknown characteristics of the distillery which made it. Frequently, the casks that are released by independent bottlers have been sold on because their characteristics do not conform to the flavour profile the distillery wants for their official bottlings. For whisky fans, though, this is a virtue: a non-conformist cask reveals aspects of character and flavour that may be hidden or absent in the distillery’s standard bottlings. 

It’s certainly true that no range of official bottlings from any distillery can ever give fans a complete picture of what that distillery is capable of. Official flavour profiles are chosen to represent the distillery’s spirit at its most typical, and idiosyncratic casks showing unusual flavours are an inconvenience to be smoothed away in large batches, or simply disposed of. The opposite is true of single cask bottlings, where the flavour is centre stage, unencumbered by the necessity to conform to its distillery’s heritage or traditions - and on this stage, for this particular audience, differences from the norm are a virtue to be celebrated.

Consequently, for whisky fans looking to explore the outer limits of a distillery’s profile, these single casks are fascinating. Each unusual or unexpected aroma and flavour opens a door to explore an alternate reality, a road not travelled, a hidden depth or quirk, a potential stylistic profile not yet fulfilled. Herein lies the true value of the best single casks: they show us possible worlds, and tell us things we never knew about our favourite distilleries. It’s almost poetic that these truths can only be shared with such a small audience. 

Many distilleries hate independent bottlers for releasing these atypical casks, but really they should be thanking them - these single casks illuminate and deepen our understanding of the distilleries that made them, and often when we return to the official bottlings we are able to view them in a new light and appreciate them more fully thanks to the similarities and differences in the single casks we’ve tasted before them.