4. Maturation

Scottish and Irish whisk(e)y gets its colour, and a large portion of its flavour, from being stored in casks for a minimum of three years. In Scotland those casks need to be made from oak, while in Ireland storage in casks made of woods other than oak is permitted. In both Scotland and Ireland oak casks that have been previously used to store American whiskey and sherry are by far the most common.

American oak

Glenmorangie The Original 10 YearGlenmorangie, founded in 1843, is home to the tallest stills in Scotland. Aged 10 years in American oak barrels, The Original serves as the flagship for...

Bourbon and Tennessee whiskey regulations require charred virgin oak to be used in its maturation. This creates a plentiful supply of used casks that can no longer be used to mature American Whiskey. Expect to notice vanilla, caramel and nutty flavours.

Further reading: https://whiskipedia.com/fundamentals/bourbon-casks/

Sherry

The Macallan 10 Year Sherry OakThe Macallan pride themselves for the quality of their Sherry casks. Indeed, they invest in tree farms from both America and Europe to control the...

Sherry casks impart more sweeter flavours to the spirit, which is quite often likened to Christmas cake or Christmas puddings. Expect to notice dried fruit and clove flavours.

Further reading:

https://topwhiskies.com/blogs/whisky-blog/sherry-casks-effect-whisky-flavour

Virgin oak

Benromach Organic One of the inherent beauties of independence is freedom. Benromach, one of the very few remaining single malt Scotch houses that’s free from the...

Whilst virgin oak is the requirement for American whiskey, it is not common in Scotland and Ireland. Where it is used, it is generally only a portion of a blend of whiskies from various types of barrels that goes into a single bottling, so as to add additional flavours to the overall flavour profile. Expect to notice vanilla, coconut, sweet ginger and oak flavours.