What is in the Barrel?

Barrel aging is an integral part of what makes whisky, whisky.  Different spirits like whisky, brandy, rum and tequila spend time in wooden barrels, but Whisky tends to have the longest maturation times in comparison to other spirits. When we look at whisky and where it is produced, we also have to understand how the colder climates of the northern hemisphere affect the time spent in the barrel.  Because we often see cooler climates this means that the spirit must spend more time in the barrel to mellow and take on flavour profiles from the wood the barrel is made of.  It is interesting to see that the further north the distillery is located the longer these whiskies spend in the barrel.  This is why we see some top-notch scotches aged for 21 to 25 years while in comparison some of the best bourbons may only spend 7 to 10 years in the barrel.  Some Distillers believe that temperature plays such an effect on the spirit being aged that barrels are also rotated to different locations on the top and bottom rows of the racking systems inside the rack house where they are stored. 

American Whiskey, Bourbon must be aged in new, charred oak barrels.  It must be distilled at no more than 160 proof and has to enter the barrel for aging at no more than 125 proof.  When bottled the spirit has to be at least 80 proof.  Bourbon cannot contain any added flavours or colouring. 

Canadian Whisky, minimum of 3 years in wooden barrels no bigger than 700 liters, new, old charred or uncharred are all acceptable.  Alcohol content may exceed 90% so it is usually blended down to around the 40% range.  As blending down can diminish some of the natural colouring and flavours from the grain, adding caramel for colouring and artificial flavouring is allowed.  But when bottled a minimum of 40% alcohol is required.   

Scotch Whisky, a minimum of 3 years in oak casks no bigger than 700 liters, however it is the practice of the trade to mature for substantially longer than the legal minimum. The whisky can be finished in multiple casks that have been used to age other wines or spirits.  Any cask used for finishing must be completely drained of all other liquid before being used for scotch.  This will ensure that any change in the spirit is a result of how it interacts with the wood of the cask.   Spirit is filled into casks at a strength of 63.5% with a minimum bottling strength of 40% alcohol by volume. 

Irish Whiskey, minimum of 3 years in wooden barrels no bigger than 700 liters.  The majority of Irish whiskeys are aged in ex-bourbon barrels made from American oak, but there are some that use ex-sherry or wine barrels made from European oak.  Generally, the spirit is 94.4% when barreled and a minimum of 40% when bottled.  Although most distillers use either American or European oak there are a few distillers that experiment with barrels made from different types of wood.

Sources:

https://www.thespruceeats.com/effect-of-aging-on-liquor-759921#why-is-whiskey-aged-longer-than-rum-and-tequila

https://www.angelsenvy.com/guide/whiskey-history/whiskey-history-how-canadian-whisky-differs-from-bourbon/#:~:text=Like%20Scotch%20and%20Irish%20whisky,mashed%20and%20distilled%20in%20Canada.

https://www.scotch-whisky.org.uk/discover/faqs/

https://www.diffordsguide.com/g/1144/irish-whiskey-uisce-beatha-eireannach/production