All single malt whiskey is aged for a length of time in warehouses, such as a dunnage warehouse. During this period, the freshly made spirit is aged in oak barrels, often known as “casks.” This is so crucial to whisky that it is sometimes codified in legislation; for example, American whiskey must be aged in virgin wood barrels, while scotch must be aged in oak casks of specified types, such as ex-sherry.
While many parts of cask maturation are codified, there is still a great deal of variation. This includes size, with barrels typically ranging between 200 and 650 liters.
Casks Used To Make Scotch
The three most prevalent barrels used in the aging of Scotch reflect both regulatory requirements and availability.
A barrel may carry around 190-220 liters of whisky (120-140 liters of pure alcohol); these barrels are frequently referred to as American standard barrels or bourbon barrels. Barrels are a byproduct of the manufacture of bourbon since the American whiskey business mandates the use of virgin oak. While American distilleries are unable to reuse these barrels, the Scotch industry not only can but often does so.
A hogshead may carry between 225 and 250 liters of whisky (142-185 liters of pure alcohol). Hogsheads are around 20 to 25 percent bigger than barrels. Coopers often remodel bourbon barrel staves into this bigger size. It is fairly uncommon for these barrels to have previously contained another liquor, such as sherry, before being used to age whisky; you may have heard the phrase “sherry hogshead.”
A butt may carry between 475 and 500 gallons of whisky (302-350 liters of pure alcohol). Thus, butts are twice the size of a hogshead and 2.5 times the size of a barrel. Sherry is often aged in butts, and in the same way that Scottish distilleries reuse bourbon barrels, they too import butts from sherry bodegas.
These barrels of varying sizes contain varying quantities of whiskey. However, there is also a significant disparity in maturation periods. A smaller cask, such as a barrel, allows for a greater ratio of wood to spirit since there is more surface area for the spirit to contact with the wood. Consequently, a shorter maturing period is required for the flavors to develop. A butt cask, on the other hand, has a lower wood-to-spirit ratio and a lengthier, more progressive maturation time.
Whisky Cask Sizes
While barrels, hogsheads, and butts are the three most frequent casks used in cask maturation, there are other cask types with varying capacities, maturation times, and in some instances, flavor profiles (for example sherry versus port).
| Type of whisky cask | Approximate number of liters | Approximate liters of pure alcohol | Typical flavor profiles | Maturation time (relative) |
| Bloodtub | 30-35 | 21-25 | Varied | Finishing or very short |
| Octave or firkin | 45-50 | 29-35 | Varied | Finishing or very short |
| Kilderkin | 90-100 | 60-70 | Bourbon | Short |
| Quarter cask | 120-125 | 84-88 | Sherry | Short to medium |
| Barrel | 190-200 | 120-140 | Bourbon | Short to medium |
| Hogshead | 225-250 | 142-175 | Bourbon | Medium |
| Barrique | 250-300 | 159-210 | Wine | Medium |
| Puncheon | 450-500 | 286-350 | Sherry | Medium |
| Butt | 475-500 | 302-350 | Sherry | Medium to long |
| Port pipe | 550-650 | 350-455 | Port | Medium to long |
| Madeira drum | 600-650 | 381-455 | Madeira wine | Long |
| Tun | 900-950 | 630-665 | Varied | Long |
Visit Whisky Cask Club if you need assistance investing in, purchasing, or selling whisky barrels.