When you buy a bottle of whisky, the label may state the type of cask or barrel that has been used during maturation. But what does the type and size of the cask really tell us?
Legally, the Scotch Whisky Regulations 2009 state that a whisky cask cannot exceed 700 litres in capacity and that the spirit must mature within it for a minimum of three years. Fail on either of these, or several other criteria, and you cannot legally name your product as Scotch whisky.
The shape and size of a whisky cask, plus what it is made from, has a profound effect on the spirit maturing within. Many people say that much of the flavour, up to 80% in fact, comes from the cask. All the natural colour does too as new make spirit coming straight from the still is transparent.
Common Whisky Cask Sizes
The size and shape of a whisky cask has a direct relationship to the spirit maturing inside. The larger the barrel, the lower the wood surface area to spirit ratio – this lessens interaction between the two. Therefore, a larger barrel is better for long maturation times. Conversely, the smaller a barrel has a greater surface area compared to the amount of liquid. Therefore, interaction is much greater.
Hogshead
The hogshead is the most common cask size found in the whisky industry. The name is derived from the old English ‘hogges hede’, an ancient unit of measurement equivalent to 63 gallons. Almost always made from American oak and used primarily in the American bourbon industry, before being passed to the secondary market. The capacity is 225 litres.
ASB (American Standard Barrel)
The rather unromantically named ASB is a smaller version of the hogshead that was developed in America for standardisation purposes. The capacity is around 200 litres. They are made from American oak and used heavily by many bourbon and Tennessee whiskey producers. These barrels are very common on the secondary market and used by many whisky producers.
Butt
This long, narrow cask with tapered ends and wide staves is most used by sherry producers in Spain and often made of Spanish or European oak. These huge casks can hold 500 litres and are the most common type of ex-sherry casks in Scotland. The large size makes them excellent for long maturation, but equally as good for a sherry finish.
Puncheon
This cask type is like a butt, but with a shorter and dumpier shape. There are two types – the ‘sherry puncheon’, which is used in the sherry industry and made using narrow staves of Spanish or European oak, and the ‘machine puncheon’, which is constructed using thick staves of American oak and used to mature rum. Both have a capacity of 500 litres.
Other Cask Types
There are several alternative sizes of cask available to whisky distillers and these range in size and shape from the massive to the tiny. We will start big and work our way down.
Gorda
This huge barrel has a capacity of 700 litres and is mostly used in America. It is the largest size that is legally allowed to be used in Scotland. They are occasionally used for maturation but are mostly filled for marrying different whiskies in a single malt or blended whisky batch.
Drum
This short, wide cask is also massive and has a capacity of 650 litres. They are made using thick staves of European oak and are specifically used to mature Madeira, the fortified wine from the Portuguese island of Madeira. They are rarely seen in Scotland or elsewhere but are occasionally used for finishing.
Pipe
Another large cask type, this time long and narrow. They are commonly made from European oak and look like a butt that has been stretched from either end. They are the main cask used to mature Port wine and are used in the Scotch industry for- finishing. Pipes have a capacity of 650 litres.
Barrique
Often used in the wine industry, a barrique is a barrel with a capacity of 250 litres. These casks are made in a different way and use wooden strips to hold the staves together, rather than metal hoops as in a traditional cask. Barriques are used mostly for finishing whisky. If you see ‘ex-red wine finish’ on a label, it will more than likely have been in a barrique for that time.
Quarter Cask
A quarter cask is exactly that – a cask that is one quarter the size of a regular cask. However, this is where confusion can begin. If the quarter cask is of American origin, then it will be 50 litres in capacity (ie: one quarter of an ASB). But if it is of European
origin, then it can anywhere between 80 and 125 litres (ie: one quarter the size of a butt). Often used to accelerate maturation due to the large interior wood surface area.
Octave
The octave follows a similar idea to the quarter cask but is one eighth the size of its parent cask type. An American octave is very small at just 25 litres, while a European octave can range from 50 to 80 litres depending on its origin. Rarely used for full maturation due to the very high wood to spirit ratio but used to finish a whisky or accelerate maturation.
Blood Tub
A small cask often used by brewers. It has a capacity of just 40 litres and is has an elongated oval shape that made it traditionally easy to carry on horseback. Not used often in the Scotch industry but can be seen occasionally if a whisky undergoes a beer cask finish or for experimentation.
Read more about the Influence of Oak Casks and Barrels on Whisky and How Whisky Casks Are Made.
