The beverage industry is closely associated with the word “barrel” which is a specific term referring to a 50–53 gallon (180–200 liter) cask, often made of white oak.
CASK as we know is a large container like a barrel, made of wooden staves and bound by wooden or metal hoops and used for ageing alcoholic drinks. A cask finish refers to a whisky that has been transferred from the primary barrel to a second (and sometimes even third) barrel for extra maturation. (The process is also known popularly as secondary maturation, double maturation or wood-finished).
So, it is said that all barrels are casks, but not all casks are barrels.
While ageing of alcoholic drinks, especially whiskey has emerged as a common occurrence now, but the practice of secondary maturation is a relatively new concept, only emerging within the past 20 years. The opinion of Distilleries also remains divided: While the Ireland’s Waterford Distillery views finishing often as a correction to a poorly made whiskey, there are plenty of drinkers and distillers that love the process and consider it a way of opening up new worlds of flavor.
Balvenie’s David Stewart was one of the first distillers to experiment with aging whisky in a different cask after it had already reached its full maturity. Almost 40 years back, in 1983 he created Balvenie Classic, which was rebranded 10 years later as Balvenie Double Wood.
At around the same time, a handful of other distillers, including Glenmorangie and Diageo, experimented with Sherry butt finishes, and within a short span of time, producers around the world, to release their own.
In just two decades, cask finishing has grown from an experimental Scottish quest for diversity into a standard practice, embracing all manner of wine, spirit and even beer casks, and widely adopted by the global industry.
Casks play a huge role in helping shape the final flavor profile of the spirits aged in them. They can impart flavors as wide-ranging as vanilla, coconut, and oak, and — when charred on the inside — help charcoal filter the spirits into smooth-sipping glory.
There are different types of casks but the main types for American whiskey range from large ones of 185 gallons to as small as for 1 gallon only.
Gorda — 185 gallons. Made from American oak. Their large size makes aging a long journey through the decades.
Port Pipe — 172 gallons. With European oak as their base, these cylindrical casks first age port and often reinvent themselves as second use barrels in Scotch distilleries.
Sherry Butt — 126–132 gallons. For ages, Scotch (and some Irish whiskey) distillers have looked to ex-sherry casks to finish their distillates and create some damn fine range of Scotch.
Hogshead — 59–66 gallons. Made from ex-bourbon barrels, often repurposed. Used especially in Scotland, coopers make hogsheads by taking apart ex-bourbon barrels and reassembling them into slightly larger casks with new ends.
American Standard Barrel — 50–53 gallons. Constructed from new American white oak or (less often) European oak, American Standard Barrels are the go-to cask used by the most well-known bourbon distillers.
Quarter Cask — 13 gallons. Manufactured to precisely 1/4 the size of an American Standard Barrel, quarter casks provide distillers with a method by which to more quickly age distillates. With 1/4 the amount of whiskey in each, the increased surface area of oak to liquid helps age whiskey more quickly.
Barracoon — 1 gallon. Roughly the size of the small oak ASW barrels which are found in local bars. The amount of wood in contact with such a small volume of liquid seriously fast-tracks the aging process but not always optimally.
Whisky must be aged in oak barrels or casks for a minimum amount of time (three years for Scotch whisky).
Cask-strength whiskey is bottled from the barrel, completely unadulterated (without being diluted with water) and is generally between 60 to 65 percent ABV.
The cask maturation of Whisky is one of the most influential processes that define the taste of Whisky. While the length of time the Whisky matures is important, the type of the cask however is crucial. The wood of the cask adds the different complex flavours to the distillery character that is already in the new made spirit. As we know by now, different casks offer different flavours.
There are five major factors that influence the Whisky in the cask:
Type of predecessor liquid – The predecessor liquid in the whisky cask also influences the taste of the whisky.
Size of the cask – The sizes of casks are very difficult to define as there is no ISO standard to define the volume of a standard cask. Most of the times, the cask sizes have been used as a unit of measurement.
Type of wood – American White Oak is a fast-growing variety with very dense wood. The monogalloyl glucose content is later transferred into the typical Bourbon vanilla taste.
European Oak – Is the most expensive variety as the growth period is longer. It contains Gallic acid which in combination with water gives the Whisky a slightly bitter note. The European oak has also a lot of other components that also add to the spiciness of the whisky.
Mizunara Oak – A common variety used for high-quality furniture. Despite lacking the waterproofing oil enzymes leading to whiskey evaporation during aging, it gained popularity because of the special aromas it gives off to Whiskey, reminiscent of sandalwood, coconut and oriental spices.
Maple – A variety that grows in many parts of the world & has low density and has been primarily used in the production of Tennessee Whiskey. Some American Whiskey producers age their new make in casks made of maple to give the Whiskeys the sweet notes of maple and maple syrup.
Charring and Toasting
The toasting and charring converts the wood sugars into vanilla and caramel flavours. The Cooper distinguishes between charring and toasting. When a barrel is charred then you burn the wood to a point where the surface breaks and leaves the wood with a surface like uneven structure. The level of charring is determined by the time the barrel is burned whereas Toasting just darkens the top of the wood and acts in the depth of the staves. It leaves the wood with a black flat layer on top.
Reuse of the cask (First Fill vs. Refill)
Oak casks are very durable and can contain Whisky for many decades. However, over the years the aroma that the Whisky can absorb from the wood decreases. The cask is leached out. Whisky that is stored in new casks therefore absorbs the most aromas.
The Scotch Whisky Association (SWA) have set specific guidance on which casks can be used to mature scotch whisky. Regardless of the type of cask used, the resulting product must have the traditional colour, taste and aroma characteristics of Scotch Whisky.’
‘The spirit must be matured in new oak casks and/or in oak casks which have only been used to mature wine (still or fortified) and/or beer/ale and/or spirits with the exception of:
wine, beer/ale or spirits produced from, or made with, stone fruits
beer/ale to which fruit, flavouring or sweetening has been added after fermentation
spirits to which fruit, flavouring or sweetening has been added after distillation
Bourbon is stored in fresh casks and is aromatic enough to be bottled after only two to five years. Scotch Whisky matures in used casks, which have already been used for e.g. Bourbon or Sherry with the wood being either American or European oak. The cask has already released a large part of the aromas. Therefore, the Scottish Malts only become really good after longer maturation. However, this also gives the Whisky more time to reduce the alcoholic spiciness. Nowadays, this historically developed system is an essential distinguishing feature between the Whisky types.
However, over the past few decades’ distillers have begun to be increasingly adventurous with their choices of casks. A master distiller might choose to move their maturing spirit into a secondary cask of a more exotic persuasion, this process is known as cask finishing. Expressions of various popular scotches have been released using rum, champagne, IPAs, cider and even tequila!
Cask is an expensive proposition; hence it is common in the Whisky industry to mature Whisky in casks more than once. A cask still contains a lot of aromas after ten years of Malt Whisky maturation and is therefore reused for the next Malt. In the industry they are called ‘refill casks’. Refill casks are reused for up to about 30 years.
In the meantime, it is more and more common to refurbish casks, as this is cheaper than buying new ones. This brings out the oak aroma again. These ‘rejuvenated’ casks make Whisky very spicy within a short time.
The labels of some Whiskey bottles sometimes indicate terms like ‘Refill’ or ‘First Fill‘, which stands for the degree of use of the casks. This gives the customer an indication of the approximate intensity of the cask aroma. Finished whiskey is technically older, and being able to include the cask finish in the age statement only helps the consumer better understand what they’re purchasing & consuming.
