In today’s current hazy IPA-dominated craft beer market, “dry-hopped” almost feels redundant. How can you have a hazy without it? More likely, it’s “double” or “triple dry-hopped” — “DDH” or “TDH.” Those three letters have come to be expected on can labels. Levels of consumer knowledge vary, but fans of New England-style IPAs delivering huge hop flavor understand dry-hopping boosts the hop aromas they seek, like tropical fruit. Because of this, some modern IPA fans might view dry-hopping as a contemporary tool for pushing the envelope on hop-saturation. It is, of course. But dry-hopping also has a history over 300 years long, one that predates the IPA and includes many other beer styles.

For those uninitiated, dry-hopping means adding hops post-boil in the brewing process (usually during fermentation or conditioning). This is done primarily because during boiling, the compounds in hops lending beer different flavors and aromas are volatile and blow off at those high temperatures. While hops in the boil contribute bitterness to a beer, dry-hopping at various points during or after fermentation gives beer tropical, citrusy, berry, and floral notes, among others. But beyond imparting flavor, dry-hopping served another critical utility back when it was first employed, and continues to serve in the evolution of flavors and drinking preferences in craft brewing today.

The Ultimate Preservative

The first written proof we have of hops being used to flavor beer is in the 8th century by German monks. And as hops’ use in brewing increased over the following centuries, they were just as valuable, if not more, for how they helped stabilize beer.

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But dry-hopping’s origin story often gets erroneously tied to the IPA exclusively. The mythologized IPA tale explains English brewers boosting the strength and hops on their pale ales to survive the ship ride to India, with dry-hopping contributing to that boost.

Historian, writer, brewer, and president of Lost Lagers beverage consultancy Mike Stein points out a few holes in this over-simplification. Pale ales in the 18th and 19th centuries were weaker than pretty much every other beer at the time. And England was actually sending more porter to India than pale ale. Per beer historian Ron Pattinson, between 1849 and 1857, the British East India Company exported nearly double the amount of porter as pale ale.

Regardless, “dry-hopping predates [the] IPA,” Pattinson writes in an email. He believes dry-hopping goes back to at least 1700; hops were added to casks for all beers, not just ones for export. By the first half of the 19th century, “it was mostly limited to pale ales,” Pattinson says, “but some brewers still dry-hopped all their beers.”

Another beer historian, Martyn Cornell, has written that 1760s-era brewers had started getting advice that extra hops were “absolutely necessary” for beer shipping off to warmer climates, but nothing links this to a specific brewery or to the India-bound pale ales in particular.

Pale ale with those extra hops, by the way, began to be referenced as “Pale Ale as prepared for India,” Cornell writes. “East India Pale Ale” shows up in an 1835 newspaper ad. Still, the extra-hopping logic would have just as easily applied to other beer styles, too.

In Mitch Steele’s book, “IPA: Brewing Techniques, Recipes and the Evolution of India Pale Ale,” he also references Cornell’s records of colonists in India trying to grow hops from the dregs left at the bottom of these shipped barrels, and of sailors trying to eat hop dregs, seeking hydration from the beer the hops would have soaked up.

Pattinson also found a description of dry-hopping touting both the flavor additions and preservative capabilities in “A Practical Treatise on Brewing,” published in 1835 by William Chadwick. “They will be found to contribute the delightful smell, and fine flavour of the hop, much more perfectly than those hops which have undergone a long boiling, and they will equally contribute to the preservation of the beer, and prevent any after-fretting that might arise.”

Dry-Hopping Comes to America

As the English colonized America and brought their brewing methods with them, dry-hopping became a part of early American beer. Pale ales that became known as India Pale Ales were dry-hopped for their journeys by sea; so were all other beers, whether bound for boats or pubs. Stein references the “American Handy-Book of Brewing, Malting and Auxiliary Trades,” published in 1902, to explain that ales and sometimes black beers received hops for storage in casks. Bavarian, Californian, Mid-Kent, and Sussex hops were recommended, in proportions of a quarter-pound to 1 pound per barrel. Essentially all beers except lagers, it seems, were considered best dry-hopped.

However, as German immigration to America swelled in the mid-19th century, a new brewing tradition took hold. Lagers steadily rose to become the style of choice, and lagers were not dry-hopped. Fewer and fewer breweries made ales; Peter Ballantine & Sons Brewing Company, in Newark, N.J., was known as one of the few IPA makers, surviving until it was sold to Falstaff Brewing Company in 1971, then to Pabst Brewing Company in 1985. Its eventual failure owes to the ongoing homogenization of beer that occurred in America post-Prohibition, as behemoth breweries — like Pabst and Anheuser-Busch — bought up the independent operations even if they had survived those years without selling alcohol. The American perception of beer streamlined into the light lager. But dedicated beer lovers like Fritz Maytag carried a torch for beers like Ballantine’s IPA, or its XXX Ale, which was one of the few American beers to be dry-hopped throughout much of the 20th century, especially since hops were no longer needed as a preservative thanks to advancing brewing technology.

Such dedication motivated Maytag to buy the then-nearly defunct Anchor Brewing Company in San Francisco in 1965. Anchor was special in that it did not make the ubiquitous light lager, but a steam beer, which uses lager yeast but ferments at ale temperatures. Maytag also had his eye on other historical beers and brewing methods, says Anchor’s assistant brewmaster, Dane Volek.

“He made a big trip to England and toured around to beef up his knowledge and understanding of things done prior but maybe not so much anymore,” Volek says. Anchor brewmaster Tom Riley adds that Maytag was interested in methods like dry-hopping and styles like porters, which were hard to find even in their native England in 1972 — homogenization had happened there, too. But Maytag did learn about the dry-hopping by which he was intrigued. And so, Anchor’s first beers to debut alongside its existing steam beer were a porter, and, in 1975, the Liberty Ale, a dry-hopped pale ale that arguably helped reignite dry-hopping and its big flavors in American beer.

Another seminal West Coast brewer was doing similar research not too long after Maytag. Before founding Sierra Nevada Brewing Company, Ken Grossman owned a homebrew shop. He studied traditional European techniques, and was paying attention to brewers close to home like Maytag. Grossman also made the pilgrimage to England, and subsequently, Celebration became Sierra Nevada’s first IPA in 1981.

“[Grossman] was using whole-cone hops in all his recipes, and Celebration was no exception,” says Sierra Nevada’s external communications manager, Ashlee Mooneyhan. “For dry-hopping, he’d stuff a sack with hops and steep, similar to a tea bag. … This method is not uncommon even today for some craft brewers and especially for homebrewers.” As batch sizes grew, Grossman and his team wanted to solve a whole cone–specific problem, which is that hops in the middle of the bag weren’t fully steeping. This led to the invention of the “hop torpedo,” a refrigerator-sized metal capsule on wheels stuffed with whole-cone hops, through which beer is circulated so it contacts all the hops. Celebration is dry-hopped with the torpedo, and also still the sack method.

Brewing teams, of course, continue to experiment and improve their methods, but often for beloved classics like Liberty Ale and Celebration IPA, the recipes remain.

Dry-Hopping’s Contemporary Craft Evolution

Anchor and Sierra Nevada’s dry-hopping with Cascade hops exemplifies how the brewers of America’s craft beer industry have taken a method over three centuries old, used for every kind of ale as much for preservation as for flavor, and made it a defining characteristic of big, hoppy, American beers.

“Americans changed dry-hopping,” says beer journalist and author Stan Hieronymus. American brewers, he explains, wanted to showcase the unique character of American hops, but were realizing the only way to get all those flavors and aromas to stay in the beer was dry-hopping so their volatile oils wouldn’t blow off. The method might have been born and raised in England and continental Europe, but American brewers continued to experiment with it to best showcase homegrown hops, just like Cascade.

Cascade hops were released in 1972. Coors wanted to get its hands on new hops not from Europe and started paying hop farmers a high price to grow varieties like Cascade. Cascade’s appeal caught on quickly. “According to a grower at the time, they recognized it had geraniol,” Hieronymus says. “When that interacts with yeast during fermentation, it creates citronella, a more tropical, fruitier, lime character in a hop.” Boiling for just 10 minutes eliminates 50 percent of that desirable geraniol, so late hopping and dry-hopping when there is still some potential for yeast activity became brewers’ method for packing their beers with those aromas.

The more flavor and aroma brewers were able to retain in their beers, the more the drinkers of these beers expected to be constantly wowed by hop character and intensity. Earlier in the 2000s, this kind of demand led to the “IBU wars,” when brewers proudly stamped ever-increasing IBU (International Bitterness Units) counts on their bottles and cans.

“It was a way of screaming, ‘We use more hops,’” Hieronymus says. “And the implication was the beer would have more aroma and flavor.”

Post-2010, though, brewers and consumers alike began seeking growing hop character without growing bitterness, which means dry-hopping. The script flipped, and suddenly brewers were racing toward being able to claim zero IBUs for their IPAs. Now, the way to convey to consumers that an IPA is bursting with hop flavor and aroma is to add “DDH” or “TDH” to the label, maybe even with the specific hops used.

American IPA drinkers’ unquenchable thirst for hop saturation and brewers’ efforts to keep up have turned dry-hopping into a forever-evolving science and industry of its own (case in point: Sierra Nevada’s hop torpedo). There’s an agronomic impact, too, Stein points out: Whereas once hop growers’ fields were mostly bittering hops with a smaller amount of aroma hops, now increasingly more acres must be allocated to aroma hops to meet brewers’ dry-hopping needs.

Hop suppliers like Yakima Chief develop products like Cryo Hops, pellets of concentrated lupulin, so brewers can add all the desirable flavors and aromas of hops to their dry-hop and still avoid potential unwanted outcomes — use too many more traditional T-90 hop pellets, for example, and/or let them sit in contact with the beer for too long, and their vegetal matter can create astringency and a green character. Plus certain hop compounds like myrcene can extract into the beer, especially when dry-hopping at higher temperatures, yielding oniony or overly resinous notes. New products and methods allow brewers to continue pushing the dry-hop envelope with positive results. They also mean brewers like Tree House Brewing Company, with its insatiable hazy IPA following, can boast they’re dry-hopping with up to 10 pounds per barrel: They can add an amount of hop product to achieve the desirable flavor and aroma effects 10 pounds of hops would yield, without the aggressive astringency such a massive amount of cones or pellets would create with all their vegetal matter.

Other beer styles can, of course, be dry-hopped — it’s essential for Italian pilsners, for example. But unlike dry-hopping’s early days, in American craft beer the method is, as Riley puts it, “a hallmark” of IPAs. It’s not just the method brewers use to get more hop character either, but also a sort of marketing tool, since adding dry-hopping information to a label instantly informs consumers they’re looking at a beer full of hop flavor and aroma.

As far as where dry-hopping will go next, it depends on fickle craft beer drinkers’ tastes. Many consumers are embracing the simplicity of lagers, but it’s hard to imagine a market where the IPA no longer has a strong fan base. Hieronymus sees sustainability and climate change concerns factoring into future dry-hopping methods and ideas, too. What hop varieties are more drought-resistant and require less water? Or are more disease-resistant so need to be sprayed less often? What hops have better performing compounds, creating more flavor and aroma in smaller amounts? Dry-hopping, and subsequently the flavors in our beers, could be shaped by what hops are most sustainable, have the smallest carbon footprint, and even are simply the most feasible to grow under harsher conditions.

From seafaring barrels and storage-room casks to engineered pellets, TDH hype IPAs, and sustainability, dry-hopping’s history is long, and nowhere near done yet.