C – as in Cask Maturation

How are whisky casks stored?

Whisky casks are usually stored horizontally. This is the traditional way of storing casks.

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How are the maturation casks stored at St. Kilian?

At St. Kilian, the whisky matures horizontally, with the casks lying on galvanised steel frames, known as racks. The opening of the cask, the bung hole, faces upwards. Each rack can hold two casks and is relatively easy to stack. Four to a maximum of five such racks can be stacked on top of each other. For this to work well, the cask sizes per rack must match in pairs. Such metal racks are widely used in the beer and wine industry.

How many racks are stacked on top of each other at St. Kilian?

In the warehouses of our Bunker City in the Odenwald, up to three such metal racks, loaded with casks, are stacked on top of each other. This storage is very similar to a traditional Scottish warehouse, known as a Dunnage Warehouse.

What is a high-bay warehouse?

A high-bay warehouse is a modern warehouse that is much larger than a dunnage warehouse and was designed for larger quantities of horizontally stored casks. The temperature in such a rack warehouse fluctuates more seasonally than in a dunnage warehouse, and within the high-bay warehouse, there can be greater temperature fluctuations between the upper and lower shelves.

Are casks always stored horizontally?

No. Whisky casks can also be stored vertically. This is the case in a so-called pallet warehouse. In this type of storage, the available space is better utilised by packing the casks closer together, placing them on wooden pallets, and stacking them. This type of cask storage is often practised in Ireland, where six casks stand on one pallet, and up to seven pallets are stacked on top of each other.

What are the advantages of horizontal storage on steel racks?

With this type of storage, where the bung hole faces upwards, it is easy to take a sample of the matured whisky from the cask. This allows the maturation level of a whisky to be checked at any time without the cask having to be moved in the warehouse – with more or less effort. Furthermore, the casks on the metal racks can be easily moved using a forklift, which significantly simplifies handling. Even entire blocks of casks can be moved in this way.

Does the position of the bung hole have to be considered for horizontal cask storage?

Not in principle. In the large high-bay warehouses in Scotland or the USA, the casks are moved into and out of the storage racks by rollers, without paying attention to the position of the bung hole. Therefore, it is necessary that the bung hole of the cask is well sealed with a wooden bung (wooden stopper) and a bung cloth. At St. Kilian, the bung hole of the cask on the steel rack is always at the top. This is also sealed with a food-safe silicone stopper, which can be easily removed from the cask in the rack, allowing convenient access for sampling.

What needs to be considered when storing vertically on pallets?

An important point when storing whisky casks vertically is the risk of leaks. When the casks are stored upside down, considerable pressure is exerted on the cask base, which is not in the direction for which the casks were designed to withstand the force. The result is often a more or less severely bulging cask head, which can lead to leaks. When casks are stored horizontally, this pressure is directed laterally downwards over the cask heads without deforming them.

Why did St. Kilian choose metal racks?

The many advantages offered by this type of cask storage led us to implement metal racks in our warehouses. For the transport and handling of the casks, which are filled at our distillery in Rüdenau and have to be transported to our warehouses in Bunker City, these galvanised steel racks are ideal and have proven to be excellent so far. In addition, this type of storage on steel racks ensures good air circulation, as the casks have sufficient space between them, which ultimately also benefits optimal maturation.

Do all casks at St. Kilian mature horizontally?

No. To a small extent, we also store casks vertically, with four casks per pallet. This applies exclusively to Bourbon casks, in order to save some space with this type of cask. We also consider this an experiment to see how this vertical storage affects the maturation of our whisky in Bourbon casks.