How are Liquor Casks Made?




Casks are like the holy grail in the liquor business. The older the cask, the more mysterious the appeal of wines and whiskies coming from it. And you will be surprised to know that despite the advancement in woodworking and kiln firing, wooden casks for ageing liquor are still made using centuries-old craftsmanship. Just like master blenders, there are master craftsmen who create casks to a distillery’s specifications.

Cask makers can alter things like the intensity of the char to create a precise chemical reaction between the wood and the liquid. Cask specifications vary depending on the liquid that goes into it, for example, rum, bourbon, whisky or sherry. But the general idea of making a liquor cask has some common features.

Felling of a tree

Oakwood is primarily used for making wine and whisky casks because of the way it grows and imparts pleasant flavors. Modern casks are generally made from French common oak, white oak or American white oak which are at least 70 years old.

Carving of the staves

Cask makers cut the oakwood into long thin planks and leave them out for drying. It removes the moisture from the wood and reduces the intensity of tannins. The way of cutting the planks is also crucial, as trees naturally have flow paths for water and nutrients and cutting along the flow paths can lead to leakages later on. Once the wood is seasoned, the planks are milled and shaped into staves. The whole process takes several years to complete, with the drying phase being the most time-consuming.

Shaping the cask

The staves are fitted around an iron hoop, making a skirt-like structure, before heat is applied to bend them into shape. The process is known as toasting and it’s traditionally done over an open flame. Toasting also caramelizes the wood sugars and breaks down the wood’s lignin to impart different flavoring qualities to the cask, e.g., caramel, nuts, liquorice, spice, vanilla and flowers. Different levels of tasting produce different effects on the cask’s wood. Once toasted, the staves are bound in metal hoops to shape the cask through continuous pressure.

Charring

While casks meant for sherry, wine and whisky are often considered complete after toasting, bourbon makes go a step forward. The casks are set on fire to create the staple 55 second Level 4 char, as by law bourbon has to be aged in new, charred barrels. Charring creates a thin layer of carbon that shields the liquid within from impurities like Sulphur.

Finishing up

Finally, the cask heads are applied to close the openings on both ends, and a bunghole is drilled for adding the spirit. Once that’s done, the cask is ready for ageing liquor. But you have to hold your horses a while because the spirit will take a minimum of three years to become your favorite whisky or wine.

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