F – like cask types

How many cask types are there at St. Kilian?

There is certainly no shortage of cask types at St Kilian. We now have over 370 different cask types and cask sizes in our warehouses. For example, the cask type bourbon barrel with a capacity of 50 litres and 190 litres counts as two cask sizes.

Does every distillery have such a variety of casks?

Almost certainly not. We are one of the very few distilleries in the world to have such a wide variety of different cask sizes and types of wood. This underlines the enormous willingness to experiment at St Kilian.

Which casks are mainly used at St Kilian?

The most commonly used barrel at St Kilian is the American bourbon barrel. We have sizes ranging from 20 litres and 50 litres to the standard barrel, the American Standard Barrel, with a capacity of 190 litres. American bourbon barrels are made from American white oak, which are charred in a cooperage and then filled in the distillery with the new make spirit known as White Dog. After years of maturing, the bourbon casks are emptied and offered for sale on the international market.

What flavours do the used bourbon barrels give off?

When the former bourbon barrels from the USA come to St. Kilian in Rüdenau and are filled with our New Make, these barrels give off the typical bourbon notes of vanilla and caramel to the maturing distillate over the years of maturation.

What other casks are available on the market?

Fortunately, a wealth of beverages, spirits and other products around the world are stored or matured in casks. Casks that have found their way to Rüdenau, for example, are those that were previously filled with sherry. These sherry casks come from the Spanish Andalusia, from the Jerez sherry region, and give off wonderful flavours of dried fruit, sherry, sultanas, chocolate and spices. Other casks used at St Kilian are those that were previously filled with apricot brandy from Turkey. But we also fill former French Pineau des Charentes casks, Sauternes casks from Bordeaux, Mexican tequila casks, Tabasco, herbal liqueur or bock beer casks.

Does St Kilian also use former wine casks?

Of course. Red wine casks in particular are highly sought after as they release wonderful aromas of red fruits into the spirit and give it a hint of tannin, which harmonises beautifully with the matured whisky and gives it structure and mouthfeel. Red wines from France, Spain or Germany usually mature in 225-litre barrique casks, wines from Burgundy in special 228-litre casks. These casks are usually made from European oak and have only been toasted before being filled with wine and not charred like the bourbon barrels from the USA.

What are the advantages of using pre-filled casks?

During seasoning with bourbon whiskey, sherry, port wine, wine or beer, the individual cask staves soaked up these liquids, as oak behaves like a sponge and eagerly absorbs liquid. If such a cask is now filled with spirit with a higher alcohol content after emptying, these ingredients are released from the staves of the maturing distillate over the course of maturation and combined with it. The flavours from the seasoning are therefore a source of the complex variety of flavours in the matured whisky.

Are unseasoned casks also used for maturing whisky?

Of course. Not every barrel made from American white oak and charred is filled with “White Dog” (New Make Spirit) in the USA, but is also sold. Such fresh, virgin casks give off more intense wood flavours to the maturing distillate. Fresh, unseasoned casks, made from Palatinate oak, Hungarian oak or the very rare Japanese Mizunara oak, are also filled with spirit in the warehouses at St. Kilian. As the European Union also allows other types of wood besides oak for maturing whisky, we are permitted to use casks made from mulberry, Swiss pear, wild robinia (pseudoacacia), ash, cedar, chestnut or cherry. The St. Kilian Signature Edition Thirteen is a wonderful example of the interplay of flavours from different fresh woods and the influence of ageing.

What sizes do the casks have?

In the whisky industry, the upper limit of a maturation cask for whisky is set at a volume of 700 litres. The St. Kilian cask with the number 1 has this maximum volume of 700 litres. In the warehouses in our Bunker City, various types of casks mature in sizes ranging from 20 litres to 700 litres.

Does the cask size influence the maturation?

Yes. The spirit matures much faster in smaller casks than in larger ones. This has to do with the surface area of wood available to the maturing spirit. According to the laws of physics, the smaller the cask, the greater the ratio of wood surface area to spirit volume. This means that with a smaller cask, there is more intensive contact between the maturing distillate and the wood. In a larger cask, on the other hand, the spirit matures more slowly and gently and the whisky becomes more harmonious, as there is less wood influence. The percentage of liquid lost from a cask during maturation (‘angel’s share’) is higher in a smaller cask than in a larger cask.

How much influence does the cask have on the maturing whisky?

Experts estimate that around 60 to 80 per cent of the final taste of the whisky is due to the influence of the cask during the years of maturation. But the quality of spirit and wood must be equally high. A poor quality distillate with many off-flavours will not mature into an outstanding whisky, even in the best wooden casks. And conversely, a very good New Make spirit poured into a wooden cask of inferior quality (e.g. a cask contaminated with mould) can only produce a mediocre whisky at best.

How old can the casks get?

Wooden casks can get very old. Oak wood in particular is very hard and extremely durable. Without physical damage, oak casks can be in use for 100 years or more. One example of this is the solera casks used for maturing sherry. When it comes to whisky, a cask is usually filled with spirit two, three or even four times in a row, depending on the philosophy of the distillery. However, the influence of the wood on the flavour of the matured whisky decreases with each use of the cask, meaning that it no longer makes economic sense to reuse the cask and it is discarded. However, it is precisely this lack of wood influence that is desirable in sherry, as the oak of the solera cask is not intended to release any flavours into the wine, but merely to serve as a dense container. These solera casks, which usually have a capacity of 600 litres and are generally made from American white oak, can reach a very advanced age. Such solera casks are highly aromatic and extremely sought-after by whisky producers. This is because their staves, which have been soaked full of ready-to-drink sherry over the very long period of maturation, release wonderful flavours into the maturing whisky.