Different whisky warehousing systems
Once a cask is filled with new make spirit, it must be matured for a minimum of three years before it can be called Scotch whisky. How is the spirit stored?
There are three types of warehousing systems used in Scotland:
Traditional (or dunnage) warehouses
Built with stone walls and sand floors, these warehouses are the type traditionally used on all sites. Stowed on wooden rails, the casks could be stored to 2 or 3 high. The atmosphere, temperature and humidity in a traditional warehouse stays relatively constant which is ideal for Scotch whisky maturation.
This is a modern alternative for warehousing and is generally used at large central sites. The racks are all made of steel (although they could be made of wood). The casks can be stowed to a height of 12 or 13. To ensure an even exposure to temperature variances, casks can be rotated from the warmer top levels to the cooler lower levels, however this is generally not required in Scotland. Unless there is a base floor which has earth rather than concrete, these warehouses tend to be drier and less humid.
Palletised is the most modern warehousing system. Casks are placed on their end on pallets and stored together in what is really just a large space. There is no requirement for wooden rails or metal racks, so this system is a very effective use of space. This is being used more for grain spirit than malt at the moment although more malt distilleries are starting to use this system. It remains to be seen whether this system will prove a success.