Bissell Brothers cask-aged its flagship IPA, Substance. Photo courtesy of Bissell Brothers Brewing

Hogshead, puncheon, foeder, tun, rundlet, firkin. These are all names for different sizes of casks historically used in brewing. Just say them out loud: a murderer’s row of great words. And don’t forget the butt (aka the imperial butt), which some claim is the root for that well-known measure of an ample amount, the “buttload” (an etymology that is not confirmed by the Oxford English Dictionary, alas).

Maine drinkers won’t encounter many “firkin-aged” ales out there, but they’ll certainly come across beers that have spent time in wooden foeders, puncheons and barrels.

Cherry Lime Times is a wood-aged sour from Allagash Brewing Co. Photo courtesy of Allagash Brewing Co.

Allagash’s newly released Cherry Lime Times – an ode to summertime cherry-lime slushies – is a beautifully made, sessionable sour that spent four months, with Maine-grown cherries, in a foudre (Allagash goes with the French spelling; “foeder” is Dutch). Fresh lime zest was added late. Effervescent and light bodied, this one is tart and acidic, but not harsh like many sour beers can be. It could be the wood talking, though wood often speaks in many – and sometimes unpredictable – voices. The porosity of barrels makes for hiding places for all kinds of microorganisms that can shape the taste of a beer, adding fruitiness, depth and complexity to Belgian-style ales.

Just a century ago, most draft beer would have been delivered in heavy oak barrels. But this doesn’t mean that those beers featured the funk. Historical evidence suggests that, since the early 19th century, brewers were quite good at neutralizing flavors from the wood (and resident microbes) by soaking it with boiling water or hydrochloric acid. In Germany and the United States, barrels were lined with pitch, both to strengthen the seal and minimize woody flavors. Eventually, wood containers were replaced by stainless steel ones.

More recently, wood has emerged as a useful (even vital) tool for craft brewers, who look to it not as a neutral container, but as an active contributor to the aroma and taste of the beer. But not all wood is the same. Different vessels have different histories, including how they were made and what they have held in the past.

Custom-made foeders can be tweaked to amplify or diminish the oak profile transmitted to the beer, which can be expressed through a range of flavors, including vanilla, coconut, almond, burnt sugar and smoke. Bourbon barrels can supply many of these aromas and flavors. Wine barrels can add a range of fruity notes. Wood can round off the sharper edges of a beer, giving it a softer body and added depth.

The size of the vessel matters as well: the smaller it is, the more contact the beer has with the wood and oxygen that, even in small amounts, penetrates from the outside. So the larger the vessel, the slower and more consistently the beer ages (but that also means longer production times). Though the sizes of vessels are variable, a puncheon is typically around three times as large as a barrel, and foeders can run anywhere from five barrels to 250 (with a more standard size being about 30 barrels).

In his influential book, “Tasting Beer,” Randy Mosher states explicitly, “barrel aging is not the best treatment for a pilsner; strong and dark is the rule.” But as with much in the craft beer world, things have changed (and quite quickly – Mosher’s book was published in 2009). As some brewers expanded their offerings, buying wood vessels for mixed-fermentation beers, they also began experimenting with “clean” beers on wood. (A “clean” beer is one in which yeasty esters, which can contribute fruitness or funkiness to the beer, are minimal, if present at all. Lagers are clean. Pale ales are relatively clean, compared to beers like farmhouse ales or hefeweizens.)

Many point to Brooklyn’s Threes Brewing as one of the initiators of this recent trend. After buying foeders for making mixed-fermentation ales, they decided to run some pilsner through it out of curiosity. The result was a beer with “wonderful subtlety,” according to the brewer. “We get this toasted-marshmallow note out of it, and it just rounds out the edges of the Pilsner.” My first encounter with a clean beer on wood was Threes’ Short Fuse, a foeder-fermented smoked helles: a beer so mind-blowingly good that the memory of the moment is branded on my brain.

Maine breweries have been experimenting with clean beer on wood recently. Last summer, Goodfire debuted Now Here Nowhere, before tweaking it earlier this year. It is a pilsner fermented and lagered for three months in a 600-liter oak puncheon that had previously held Cabernet Sauvignon. It is then returned to stainless tanks, where it is blended with fresh, still-fermenting lager, producing natural carbonation (a traditional process known as “krausening”). Aromas of oaky vanilla and berry mingle with the floral hoppiness of a pilsner, with slightly softer mouthfeel that retains the crispy finish characteristic of the style.

Belleflower recently released Lost Leaf Oak, a Czech-style pale lager matured in neutral wine barrels. There is a verdant woodiness in the initial approach, but as the beer warms, it is increasingly reminiscent of an oaked Chardonnay. A citrusy brightness mingles with the malt in the background.

Bissell Brothers has made heavy use of its foeders to make mixed-fermentation ales and saisons at their Milo location. Their first “clean” foeder-aged beer just debuted – using their flagship IPA, Substance. Aromas of orange candy replace the dankness of the regular version; as it warms up in the glass, hints of wood emerge. Where standard Substance is loud and hot, bristling with bitter citrus and earthy garlic-onion, the foeder version is self-possessed and cool, with a “hard-to-define gentleness,” as brewer Noah Bissell says. It’s a fascinating illustration of how even a little time in wood transforms a beer.

Contemporary brewers must reckon with the demands of impatient drinkers clamoring for the next thing, which often results in juicing new beers with bolder flavors and quirky ingredients. But re-pitching brewing traditions in new ways – like reintroducing clean beers to wood – is a welcome mode of innovation.

Ben Lisle is an assistant professor of American Studies at Colby College. He lives among the breweries in Portland’s East Bayside, where he writes about cultural history, urban geography and craft beer culture. Reach him on Twitter at @bdlisle.