Everything You Need to Know - Our guide to Oak Whisky Casks
This our complete guide to oak whisky casks - everything you need to know. It is impossible to overstate the symbiotic importance of oak when it comes to making world-class whisky. When whisky first comes out of the still, it is clear, and imparts our distillery's characteristics - the birthplace of our DNA. Only while resting in oak casks is whisky coaxed to develop its full complexity, flavour, colour, and fragrance.
Conceived for the purpose of storing and transporting bulk goods, wooden casks have been built and used by humans for thousands of years. Ancient Greek geographer and historian, Herodotus, wrote about a visit to Babylon in 450 BCE where he observed wine casks being constructed of palm wood.
Used to import Armenian wine from Mesopotamia, the casks described by Herodotus were not the first vessels employed in the transport of alcohol, explains The Whisky Exchange. That distinction goes to a pottery shard that dates back to approximately 7000 BCE
So far, nobody has determined who, exactly, invented the wooden cask. Ancient Egyptian murals do provide a hint, however. When the tomb of Third Dynasty official, Hesy-Ra was excavated in 1910, British archaeologist James Edward Quibell found a mural depicting a wheat-measuring, cask-like tub made of wood and held together with hoops. Another ancient tomb painting dating back to 1900 BCE clearly shows a cask maker, or cooper, constructing a staved cask intended for use at grape harvest time.
Watertight staved casks bound with hoops may have been invented by the ancient Celts, who used them to transport everything from honey to nails, says River Drive Cooperage, noting that the long-ago Europeans had ready access to timber and probably devised barrels as we know them today sometime around 300 BCE.
No matter who first invented the oak cask, we offer them a hearty round of applause, because without oak casks, whisky as we know and love it today would not exist.
You bet they are. Before ageing in oak, whisky contains a number of unwanted flavours. Sherry matured Oak casks such as those used here at Callington not only remove those unwanted flavours, they impart several much-appreciated notes of their own.
Oak influences whisky in a profound way, and it's not just taste that is involved. Ageing in oak barrels also develops the warm brown colour that whisky aficionados admire. Depending on the species of oak used to build a cask, the wood may impart a flavour of vanilla, dark red fruit, citrus zest, or vanilla, explains Whisky Advocate who also says that if you want to understand whisky, you must first understand oak.
Not just any wood can be used to build a whisky cask. Irish whisky maker Kevin O'Gorman offers a scientific explanation that Quercus alba, or white oak is a popular timber for casks due to the way certain cells called tyloses dam the tree's vascular tissue and prevent leakage. By allowing oxygen to move back and forth, the oak facilitates a number of remarkable chemical reactions.
Slower-growing and at least as flavourful as white oak is Quercus robur, or the pedunculate European oak that is used predominantly in the Spanish sherry industry. Oak casks toasted or charred before being filled with fortified sherry wine that imparts a certain spiciness and a hint of dried fruit flavour to whisky as it matures.
Amazing chemical processes called reactive mechanisms occur when spirits age in oak. These chemical alterations give single malt whisky its splendid colour, mature notes, and aromatic bouquet.
Subtractive reaction happens when undesirable compounds come on contact with charred barrel wood and/or evaporate as the spirits breathe.
Additive reaction occurs as oak imparts a range of subtle flavours such as leather, smoke, vanilla, and caramel. Vanilla flavours come courtesy of lignin, while lactones are responsible for adding buttery or coco-nutty notes. Tannins provide balanced dryness and woodsy spice flavour. Master whisky makers know how to time ageing, so bitter tannins don't overpower subtler, more desirable flavours.
Made of curved staves and held together with hoops, casks are shaped the way they are for very good reasons. So good, in fact, that the barrel shape has remained the same for centuries.
Built by a craftsman called a cooper, casks are wider in the middle than at either flat end. The bulging part of a cask is called the bilge. The curvature of the staves contributes to a cask's overall strength.
Unlike cylinders that can be rolled but are hard to steer, a convex cask can be coaxed to change direction easily. Casks can also be stacked in a sideways position with little blocking required except for the bottom row.
Casks come in a number of sizes, explains Whisky. The most popular are:
● Bourbon Barrel: Aka American Standard (ASB) holds 53 US gallons/ about 200 litres
● Hogshead: Made of reclaimed staves and holds 59-66 US gallons/ about 225-250 litres
● Butt Barrel: Long, thin sherry casks that hold up to 500 litres
● Pipe: Similar to sherry butts, hold up to 650 litres
● Quarter Barrel: 50 litres
● Quarter Butt: 125 litres
● Octave One-eighth of a Butt / 50 litres
● Blood Tub: The smallest cask holds 30 to 50 litres / sometimes sold full by distillers
As the only whisky distiller in Taz to boast its own cooperage, Callington Mill Distillery is rightfully proud of our Callington Mill Cooperage.
The cooperage team have searched the world for the finest quality oak casks. Many of our casks include Tawny or Port casks from Portugal, French cognac casks, premium ex-bourbon casks from Kentucky, authentic Jamaican rum casks, exclusive Madeira wine casks from California and many more. Each cask brings an exclusive and unique flavour and colour to our premium single malt whiskies.
The number of years a whisky is aged matters, of course, but so does the barrel in which it matures. The particular oak tree involved, the oak species, and the manner in which the barrel was toasted and seasoned all factor into the creation of a world-class whisky
And why do we take the time? Because the world’s finest whiskies require the world’s rarest casks.