Warehouse choice and system stacks casks' final flavour
Distillery tours often include a visit to the warehouse to see hundreds of casks, working their magic and turning new-make spirit into something wonderful.
Most people at this point are shuffling towards the tasting room. But whisky nerds like myself will be geeking out over the type of storage system being used.
Generally speaking, there are three types of warehouses: the traditional dunnage, the more modern racked style and most efficient palletised.
Racked warehouses were first used in the 1950s. Casks are stacked on their sides, eight or 12 high on steel racks, in long, parallel rows.
Palletised warehouses store casks upright on pallets up to eight high. Both systems are very efficient and allow casks to be easily moved around using a forklift.
The classic dunnage warehouse is the least glamorous. Normally it’s an old, thick stone building with no windows and a low slate and timber roof, littered with spider webs.
Casks are manually stored in rows, known as stows, two or three high, with wooden floors dividing the levels.
You may be surprised that this is where they keep the ‘good stuff’. Why? Well the earth floor keeps humidity fairly high and the structure keeps a cool, stable temperature throughout the year. This encourages increased evaporative losses of ethanol rather than water, leading to a slow reduction in alcoholic strength.
Casks at the top of a racked warehouse can be five to eight degrees warmer than those stored at the bottom. Humidity also reduces the higher you go, which means the whisky matures differently.
There are pros and cons to each system and unless a distillery is looking to release a single cask whisky, it will combine a variety of casks to create its final expression which will balance minor differences between casks.
Dunnage warehouses are my favourite. But that’s easy to say when you’re not the one shifting hundreds of casks a week by hand!
- Matt MacPherson is the owner and founder of The Malt Room in Inverness.