Scottish whisky must be matured in oak casks. It’s the law.
Much of the flavour of a whisky comes from the cask. And although it has to be oak, a surprising amount of leeway is permitted in just what kind of casks these can be, where they come from, and the flavours they impart.
Let’s get to the detail. Most casks are made from American white oak, and a small percentage are made from European oak. American oak gives a gold colour and vanilla flavours. The European oak is more tannic, so gives a richer colour and more dried fruit and spice to the flavour. Find out here how whisky casks are made.
Casks are in general never used new, they’ve already been used to age other alcoholic drinks– bourbon, sherry, wine and port, to name a few. There have been great experiments in using different casks and we’ve highlighted a few of these in our ‘whiskies of the week’.
Casks become exhausted after being used three or four times. They can be renewed by being scraped out and re-charred. Luckily the bourbon and wine industries produce a great deal of casks.
The most common size of barrel holds around two hundred litres – barrels or ‘American standard barrels’. Another interesting fact – When four of these are taken apart, they can be used to make three Hogsheads, which are around two hundred and fifty litres.
To be called ‘Scotch whisky’, the spirit must be matured in Scotland for a minimum of three years. There are different types of warehouse, some warehouses have the casks sitting on top of one another, others store them on pallets which are slotted into tall frames.
However they are stored, it is affecting to be in a warehouse, surrounded by sleeping casks. They seem to sit quietly and time feels different when you are in their midst. It makes you slow down and reflect on your life. Where will you be in ten, fifteen, twenty years when these casks see the light of day again?
The angel’s share is a lovely idea. As they wait, the walls of the cask breathe. It releases harsher alcohols and welcomes water in, which dilutes the spirit. So you can see why the whiskies that each distillery produces are unique. No two have the same conditions, the same air, the same climate.
There’s something about the life cycle of casks that is really alluring: they start off life in other countries, filled with other drinks; they carry such complex flavour in the wood; they can be taken apart and re-made; and they can be given new life with fire.
They are essential to the journey of the spirit, quietly breathing life into it until one day, you open the bottle and taste what time has created.
If you’ve ever considered buying a cask, this will be worth a read.