Whisky in Virgin Oak Casks

1. Origin

Fresh white oak casks, or 'Virgin Oak' casks, are mainly used for Whiskey maturation in the USA. This is because the American law (Bourbon Act) stipulates that Whiskey must mature for at least two years in charred new oak containers. Maturation in fresh white oak casks is not so widespread in the production of Scotch Whisky. Usually a Virgin Oak cask is only used for a finish. Full maturation is rare, as there is a risk that the oak will overpower the other aromas in the Whisky.

2. Production

So Virgin Oak casks have not been filled before Whisky is stored in them. They are made in the cooperage and then sent directly to the distilleries. Mainly the type 'Quercus alba' (American white oak) is used for the casks. This is because this type grows quickly and gives the Whisky vanilla and caramel aromas. In addition, Scotland does not have so many forests and therefore not so much wood for casks, compared to the USA.

Buying a fresh Virgin Oak cask is a bigger investment for a distillery than buying a used Bourbon, Sherry or Wine cask.

Before the Whisky matures in the cask, the cask is toasted and charred. During toasting, the cask is heated to at least 150°C. This splits the cellulose in the staves into wood sugar, which at these high temperatures begins to caramelise. Only after this process does the cask release the familiar caramel, vanilla and coconut aromas into the Whisky. When the cask is then charred, a large flame goes directly into the cask, creating a dark layer of activated charcoal on the inner wall of the cask. This helps to filter out the pungent tastes and aromas from the Whisky during maturation. The layer works just like an activated carbon filter. During toasting and charring, the distillery can vary the duration and depth of activation depending on the desired result.

3. Effect on Taste

A freshly toasted cask gives off particularly many vanilla and clove aromas (vanillin and eugenol) to the Whisky. In taste, vanilla, sweet ginger and coconut come to the fore. With its intense oak notes, Virgin Oak especially makes younger Whiskies (without age indication) appear more mature and gives them more depth. But this is also the crux of Virgin Oak: Since these strong oak notes sometimes mask the rest of the aromas, full maturation is rather rare. However, a finish can add an interesting dimension to the Whisky bouquet. After all, the result depends on the skill of the blender.

4. Effect on the Colour

The caramel, which is created by toasting and charring the cask, gives the Whisky its dark colour. We know this from American Whiskey, which is very dark although it usually only matures in casks for two to four years. The dark colour of the Whisky only comes from the cask. Because a fresh cask not only has more aromas but also more colour to give off than a refilled one.

For this reason, Scotch Whisky usually turns out much brighter when using ex-Bourbon casks. The oak has already given off much colour to the Bourbon. Virgin Oak casks, even during finishing, give Scotch Whisky a darker colour.