Cask finishing in whisky: what a finish adds and what it can hide

What a finish is

Most whisky matures in one type of cask for most of its life. In Scotland and India that is very often an ex-bourbon barrel, an American oak cask of roughly 200 litres that previously held bourbon. A finish is a second, shorter period in a different cask, usually one that held something else: sherry, port, red wine, rum, Madeira or another drink.

The finishing period might be a few months or a couple of years. The idea is to add a top layer of flavour from the second cask without losing the character built up in the first. Labels often say "finished in" or "double matured". Our guide to whisky label terms explains the wording.

What different casks add

• Sherry casks. Oloroso casks bring dried fruit, nuts, dark chocolate and spice. Pedro Ximénez casks give richer, sweeter raisin and fig notes.
• Port casks. Red berry, plum and a slightly sweet, wine-like edge. Often a pinkish tint.
• Red wine casks. Berry fruit and some tannic grip.
• Rum casks. Tropical fruit, brown sugar and banana notes.
• Virgin or heavily toasted oak. More vanilla, spice and wood tannin, sometimes too much.

The size of the cask matters as well. A sherry butt holds about 500 litres. A port pipe is a similar large size. A barrel is about 200 litres. Smaller casks have more wood surface per litre, so they work faster and can overwhelm a spirit sooner.

How finishing fits into maturation

Maturation does three things: the wood adds flavour and colour, the wood removes some harsh, sulphury new-spirit notes and slow oxidation through the cask develops complexity. All three continue during a finish, but the main point is the first. The second cask's previous contents, soaked into the wood, add their own character.

For the bigger picture of how casks shape whisky, read whisky maturation and casks.

Climate changes the timetable. In India's heat, whisky draws flavour from wood faster than in Scotland. More spirit also evaporates each year. A finish that takes a year in a cool Scottish warehouse may need careful monitoring after a few months in a hot Indian one. Distillers sample finishing casks regularly so the second cask does not take over.

Age statements and finishing

An age statement on a bottle refers to the youngest whisky in it, counting all its time in wood. Time in the finishing cask counts. A 12 year old whisky finished in sherry casks for one year has spent 11 years in its first cask and one in the second, or some similar split. The label might not tell you the split. Our guide to whisky age statements covers this in more detail.

Rules differ by country. Scotch whisky regulations set out which casks are acceptable. Producers elsewhere follow their own national rules. Labels must not mislead, but they do not always explain much either.

What a finish can hide

Here is the uncomfortable part. A strong finishing cask can cover a lot. Young spirit that still tastes raw, a tired first cask that gave little flavour or a spirit with off notes can be dressed up with a few months of sweet sherry or port wood. The result can taste pleasant at first sip and then fall flat, with the finish sitting on top rather than woven in.

Signs a finish is doing the heavy lifting:

• The cask flavour arrives first and loudly, then the whisky underneath tastes thin or hot.
• The fruit or sweetness feels separate from the cereal and oak, like two drinks in one glass.
• Adding a few drops of water makes the whisky fall apart rather than open up.

A good finish is integrated. The second cask adds depth but you can still taste the distillery's spirit and the first cask beneath it.

Taste it for yourself

The best way to understand finishing is to compare. If a distillery releases the same whisky in a standard version and a finished version, taste them side by side in small measures. Note what the finish adds and what, if anything, it covers. Then add a little water to each and see which holds together.

That kind of comparison is how distillers make decisions too. They taste finishing casks repeatedly to decide when the balance is right. The craft is knowing when to stop.