Maturation in Irish Whiskey

Author - Anthony Gannon is a final year student on the brewing and distilling course at IT Carlow. He has written the following piece on the maturation process which we recently used at Flying Tumbler. 

Anthony Gannon

Distillers live in a world where their mistakes don't catch up to them until many years after they have made them. This is because, at the very heart of distillation, lies a mystical and esoteric art called maturation.

Unlike Gin and Vodka, Whiskey can not be bottled straight from the still. It must spend a number of years inside a wooden container called a cask. In Ireland, it is mandated that Irish whiskey must spend a minimum of three years within a cask though in reality whiskey spends much longer maturing. Irish whiskey that is not matured is called Poteen.

It is during this maturation process that the colorless spirit from the still takes on its golden brown color, its aroma and; perhaps most importantly, its taste. Since maturation is such an important component of the whiskey production process it is worth exploring here and seeing how Flying Tumbler does it.

 Usually casks used for the production of Irish whiskey begin life in America. White Oak trees are chopped down and the segment of the log called the Heartwood is cut out and plyed into narrow planks called staves. These staves are bound together by metal hoops and form the body of the cask.  The interior of the cask is then toasted, sometimes heavily and sometimes lightly; it all depends on the preference of the distillery. The level of toasting, also called charring, impacts on the flavour and color of the final product. A light char will produce a correspondingly light coloured whiskey with a more organic or floral taste. A more heavily charred one will produce a darker whiskey with toasted flavours.

 These barrels are brand new and so they are called 'Virgin'. These virgin barrels are used for the production of Bourbon whiskey. They are used only once and once the maturation period for the bourbon is over the barrels are disassembled and sold. This is where Irish whiskey distillers come into play. These former bourbon casks are exported to Ireland where they are reassembled and filled with Irish whiskey. It is at this point that we discover the importance of the cask's pervious history.

When you fill a cask with something; be it Whiskey or Beer or Wine, a portion of the 'essence' of the maturing liquid will be left behind in the wood. This is important because the retained essence will impact the flavour of every proceeding maturation in that cask. The more times the cask is used and the greater variety of things that have been matured in it then we see a greater complexity of flavours and aromas being imparted by the maturation process.

It is for this reason that Irish whiskey distillers source a number of different types of casks to produce their Whiskey. The main type used today is a former Bourbon cask but former Sherry casks from France are becoming increasingly popular along with Wine and Port casks. These all impart unique flavours to the maturing whiskey. These flavours combine with those given by the cask wood and held already by the distilled spirit. A blender must have a good nose and taste for these things when they combine Whiskies from different cask types with different histories. It is their judgement of the individual flavours and aromas that determines if the end product is consistent batch to batch.

 Speaking of blending. How does a person go about ensuring consistency of flavour when two types of cask or more need to be blended? How can we ensure that the maturation we are about to wait upwards of three years to finish does not give us a completly undesirable taste or aroma or colour?

One way is to cut the number of variables, and therefore things that could go wrong, down. This is done by a process called 'Marrying' .

Marrying is a process in which two or more types of whiskey are matured in the same cask. This can be done 'At Birth' which is where the new make spirits are compined in the cask straight away once it is distilled. The other type of marrying occurs when two or more spirits are matured individually in their own casks for a period and then combined in another cask to mature for a further period. The latter is the type of marrying performed at Flying Tumbler. It allows for a greater degree of flavour and aroma complexity to develop in the spirit and accelerates the blending process significantly. This form of marrying also allows for greater control over the final product and a reduction of errors that could be made during the blending process.

 The casks we use here in Flying tumbler are as follows. Former Bourbon, which imparts aromas and flavours of toffee, vanilla, brown sugar and baking spices along with a mild palate. We also use Californian wine casks which impart fruity flavours with a flowery aroma. Finally we use sherry casks from Maine which also imparts rich sherry flavours.

 Our blending process is artisanal and utilises traditional methods. Calibrated glass hydrometers are used to measure the % ABV of each spirit and are also used to monitor the blending process. This is a highly accurate method that gives us a greater degree of control over the production of our spirit and ensures consistency between batches. Furthermore the water we use during cutting and blending is Reverse Osmosis water which is currently the most pure type of water available. This allows us to cut out any potential contaminants from the mains supply and also gives us further control over the blending process. The water does not contribute any of its own flavours or aromas to the spirit, thus leaving us with a product that derives its profile exclusively from the whiskey itself and nothing else.

 Once the processes of maturation, disgorging, blending and cutting are done we move on, at long last, to bottling and packaging. Here we employ a 'cuckoo' model for bottling. This means we utilise  a mobile bottling installation to pour our matured and blended spirit into bottles which are then sealed and packaged. This is an ideal set up for a new whiskey brand as it is low cost and effective.