Behind The Scenes: Cask Maturation

Every stage of the production process is important to the creation of a whisky but one of the most fundamental (and longest!) stages is maturation. At Kilchoman we are proud that 100% of our spirit is matured on Islay, allowing the local climate to affect the character as it ages. We fill every cask at 63.5% ABV with water from Glen Osamail, a burn that runs from the hill behind the distillery. And then we wait!

We currently have eight warehouses, maturing in a combination of racked and dunnage. Dunnage is very traditional, with casks only being stowed 3 high on earth floors. Whereas our newly built racked warehouses can hold casks 10 high. We look forward to analysing any subtle differences in character that may come from using these two types of warehouses.

The legal requirement to be Single Malt Whisky is a minimum maturation of 3 years and 1 day in oak casks. We source our casks from all over the world and they vary in style, size, shape and of course influence on the whisky.

At Kilchoman we predominantly mature in ex American Oak bourbon barrels. We feel this best allows Kilchoman new make spirit to shine through. Bourbon casks are the most widely used cask type in Scotland due to their consistency in flavour and reliable supply, making them the perfect candidate for one of our core range expressions – Machir Bay. Each cask has a 200L capacity and will generally impart more flavours of vanilla, butterscotch and oak.

The other most commonly used cask type is ex Sherry casks, more specifically oloroso sherry. We source all our sherry casks directly from Bodega Miguel Martin in Spain, an independent family run company like us. These come in a range of sizes, from Hogsheads (225 – 250 litres) or Butts (475-500 litres) and will typically give flavours of rich dried fruit, warm spices and nuttiness. Oloroso is not the only type of sherry we use at Kilchoman, we also fill into PX, a much sweeter style of sherry, and Fino, a drier style. Despite filling more bourbon barrels than sherry casks, we still love the way sherry casks illustrate the richer, deeper flavours in our whisky and showcases our spirit in a different light, as you will find with our Sanaig release.

We have always enjoyed experimenting with cask types and have tried various options such as Port, Madeira, Sauternes, Red Wine, and the list goes on. In 2019 the Scotch Whisky Association eased restrictions on the types of casks that can be used for maturation, allowing us to become even more experimental, filling casks such as Tequila, Mezcal and Calvados. The whisky industry is constantly evolving, and it is always exciting for us when we can try something new and create different flavours at Kilchoman.

In contrast to most distilleries who use these ‘experimental’ cask types for short periods of finishing at the end of maturation, we prefer a full-term maturation for many of these limited edition expressions, such as the 2024 releases of Port and Sauternes Cask Matured. This can be a risky strategy as these cask types are renowned for imparting bold and powerful flavours which we wouldn’t want to dominate the Kilchoman spirit. However, we have found the full impact of these casks can produce something special and unique in the final creation.

Using all these different cask types not only allows for a lot of different flavours to shine through but also creates a wide range of colours. All Kilchoman’s whisky is completely natural in colour and free from any additives such as caramel. All our colour comes completely from the cask it was matured in, with bourbon barrels giving a bright golden colour to the spirit and sherry casks providing a much darker, deeper tone.

While the industry norm is to use casks several times for maturation, exhausting all that the cask has to offer, every cask that we source will only be filled twice by us and will then be sold further into the industry to be used again. This ensures we get the maximum impact of flavour in our maturation to create our bold, fresh, full of character single malt whisky. It’s a common misconception that whisky must be old to be considered good. Although age is a vital part of any whiskies flavour profile, there are many other important factors that go into the makeup of a whiskies overall character, and it is a combination of all these elements that define the unique style of Kilchoman – from barley to bottle.

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