Cask Finishes Explained: Stout Casks, Sherry Casks and the Beer-Whiskey Barrel Trade

Cask FinishesExplained

A cask finish is a second, shorter stint of aging: a whiskey that has already matured in its first barrel is moved into a different cask, often one that previously held sherry, wine, rum, tequila or beer, to pick up extra flavor. Breweries and distilleries also trade barrels in the other direction, so a bourbon barrel can age a stout, and that stout-soaked barrel can then go back to finish a whiskey.

Every whiskey gets much of its color and flavor from wood. In the main maturation, spirit sits in a barrel for years, drawing vanilla, caramel and spice from the oak while slow oxidation softens it. A finish adds a second chapter. The matured whiskey is moved into a cask with a different history for an extra period that varies widely by producer and cask.

The finishing cask contributes in two ways. Wood that has soaked up a previous liquid releases some of it back into the whiskey, and that previous liquid has also changed the oak's chemistry. Distillers debate which effect matters more, but both shape the result. The cask's size, char level and how many times it has been used all affect how strong the finish is.

Balance is the craft. A powerful cask can overwhelm a light spirit, so producers pair the whiskey and the finishing cask carefully and taste often.

Under federal standards of identity, bourbon must be made from a mash of at least 51% corn, distilled at no more than 160 proof, entered into the barrel at no more than 125 proof, and stored in new charred oak containers. That first barrel is non-negotiable. A finished whiskey starts as bourbon that meets those rules, then spends additional time in another cask. Because that second cask is used rather than new, federal regulators (TTB) treat the result as a distilled spirits specialty, not plain bourbon, so the label has to say what happened: "bourbon whisky finished in sherry casks," for example.

Sherry casks are the classic finishing barrel, especially in Scotch whisky, where the practice took hold. Sherry is a fortified wine from southern Spain, and its styles bring different flavors to the wood:

• Oloroso: nutty, dried fruit, a little savory.
• Pedro Ximenez (PX): very sweet, with raisin, fig and molasses notes.

In bourbon, a sherry finish usually adds dried fruit, darker sweetness and a rounder texture on top of the familiar vanilla and caramel. Done well, it reads like a layer, not a costume.

Stout-cask finishing is a good example of how beer and whiskey trade barrels. A widely known case started in 2013 in Ireland, when the Jameson distillery sent whiskey barrels to Franciscan Well, a Cork brewery, which aged a stout in them. The beer-seasoned barrels then went back to the distillery and were refilled with whiskey. The finished whiskey picked up notes of coffee, cocoa and a hint of hops.

The same idea applies to bourbon. A brewery ages a stout in used bourbon barrels, the barrels return to whiskey duty, and the bourbon that comes out carries roasty, chocolatey and sometimes slightly malty notes from the beer.

One of the best-known early examples of brewers borrowing spirit barrels came from Chicago. Goose Island aged an imperial stout in Jim Beam bourbon barrels for its thousandth batch. The brewery dates the first batch of what became Bourbon County Stout to 1992, though some beer historians argue it was more likely 1994. Either way, it helped launch an entire category.

Because bourbon must go into new barrels, the industry produces a steady supply of used ones, and many end up at breweries. Bourbon barrels give beer vanilla, coconut, caramel and toasted oak notes, plus some of the spirit's character. Our guide to barrel-aged beer covers how brewers use them, and porter vs stout explains the styles that most often go into the wood.

• Taste the base first if you can. Comparing a finished bottle to its unfinished sibling shows exactly what the cask added.
• Look for layers. Sherry tends to show up as dried fruit; stout as roast and cocoa; tequila as a light, peppery, agave-like note.
• Go slowly. Small pours, a glass with a narrowing rim, and a few minutes of air all help. Our guides on beer glassware and how to taste beer apply to spirits, too.

Lonerider Spirits offers bourbon whiskey finished in sherry casks, stout casks and tequila casks; see the spirits lineup.