Whiskey casks – what you need to know
Whiskey cannot be officially classed as ‘whiskey’ until is it ‘laid down’, or stored, in a cask for at least 3 years. So what is a cask? A cask is a wooden barrel that is used to store whiskey as it matures. Casks are typically made of oak. They vary in size, from 50 litres capacity all the way up to 700 litres.
Casks are made in Cooperages, by skilled craftspeople known as Coopers. Cask making is highly-skilled and specialised, with the skills and knowledge about this process being passed from generation to generation.
In America, for a bourbon to be officially classed as a ‘bourbon’, it is required by law to be aged in a new barrel – i.e. a brand new cask that hasn’t stored any other liquid.
However in Ireland and Scotland, new casks are not a requirement, so we can choose the type of cask to age our whiskey. Many whiskeys in Ireland, Scotland and beyond are aged in ex-Bourbon casks, as well as other oak casks which have previously contained liquids such as fortified wines.
Casks that have previously been used to age other spirits, impose a different range of flavours on the maturing whiskey within. There is a considerable debate in the whiskey world as to how much influence the cask has over the whiskey taste – some reckon that up to 80% of the whiskey’s overall flavour comes from the cask.
While we’re not sure exactly what percentage of the flavour is determined by the cask, what we are sure of is that high-quality casks produce high-quality whiskeys.
What determines a high-quality cask?
- Origin of the wood – American oak gives a softer, sweeter taste with notes of vanilla and caramel, while European oak is spicier and has a stronger wood input. European oak grows in northern Spain and Portugal. French oak is used to age wine and cognac. It will bring notes of vanilla, pepper and subtle spiciness.
- What spirit was previously in it, if there was anything in it before e.g. sherry would have left its flavour profile within the wood. Casks could also have contained port or even cider, and each one imposes its own unique flavour profile on the whiskey.
- Condition of the cask at casking – i.e is the Cask “wet” or “dry” when the whiskey is put into it? A wet sherry cask has just had the sherry removed, and so is still ‘wet’ – this will impose an instant strong flavour profile. Whereas a ‘dry” cask has been allowed to dry out after its previous spirit was removed – which delivers a taste profile that is not as imposing and more subtle.
Every Cask is different, as they are all handmade – the staves are different (the wooden slats), so each cask has its own identity, and you have to treat it as such.
The interior of the casks undergoes a heat treatment which contributes to the flavour profile of the new make spirit. There are two options for applying this heat to the inside of the barrels, a fast short burn (charring) and a longer gentle heat (toasting).
Charring is a process that can be described as a fast burning of the inside of a cask where the intense heat results in a burnt appearance. The interior of the cask turns black with a charred residue that acts as filtration and removes some undesirable flavours such as sulphur. The intense heat caramelises the sugars in the oak which imparts a sweeter flavour along with caramel notes, vanillins and some tannins along with a deep and dark colour to the spirit.
Charring also allows deeper penetration by the spirit and it’s that intense interaction with the oak that gives it more flavour. Charred casks impart vanillin flavours, smoky notes, caramel, honey and spice.
Compared to charring, toasting is a slower process where the barrels are heated gently which results in the oak having a dark brown colour rather than a blackened char. The slow and gentle burn means the sugars in the oak do not have enough time to caramelise. As such, the spirit is lighter in colour and not as sweet as one from a charred cask.
Toasted casks impart some nuttiness, light vanilla flavours, and some sweet notes akin to a light caramel and toffee.
One of the art forms of whiskey is how you blend the casks together – you can make a cask up of a couple of different casks if you like – you could have a 50% port cask and a 50% bourbon cask. One of the exciting opportunities in Irish Whiskey is that the rules and regulations give us room to experiment – we can use non-oak casks, for example, cherry or acacia casks – which can result in the most incredible and unique whiskey. (Scottish and American whiskeys have to be aged in oak)
Why is cask membership so appealing?
Whiskey making is a supreme art, where the real value lies in individual expression, so cask membership allows you to select your own unique cask – a chance for your whiskey to be completely unique.
When fully matured, your whiskey will be an expression of who you are. Cask membership offers you the opportunity to craft your own style of whiskey, have a play around with different taste profiles and ultimately create a whiskey that is one in a million.
Also, we produce one small batch of Curraghmore Whiskey per year making our whiskey rare and exclusive.
There are many types of casks available, and it can be overwhelming when trying to decide which type of cask you should store your whiskey in. We’re here to help – Contact Richard any time if you have any questions.