Beyond Beer: The Art & Science of Hard Seltzer

To brew a quality product and set it apart in an increasingly crowded market, there is a lot more to know than how to ferment sugary water. Here, we lay out some specific technical considerations for brewing better hard seltzer, properly and safely.

Joe Stange , Jamie Bogner Feb 10, 2021 - 14 min read

Beyond Beer: The Art & Science of Hard Seltzer Primary Image

The base ingredients are cheap, it doesn’t take long to make, and you already have most of the equipment you need. The pragmatic advantages of brewing hard seltzer are as clear as the drink itself.

On the other hand: The segment is increasingly crowded with small players, and you have (we hope) put a lot of work into earning a reputation for beers of quality and character. Hard seltzer isn’t beer, but if you’re going to make it, you should consider applying the same approach to details and fine-tuning, so you end up with a product of which you and your team can be proud.

Besides speaking with many professional brewers about their processes—for this article and others—we also spoke with Chris Colby, author of the recently published Brewers Publications book How to Make Hard Seltzer. (For more from Colby, check out Craft Beer & Brewing Podcast Episode 151). Here, based on their advice, we sketch out some key technical considerations for making better hard seltzer, keeping breweries of different sizes in mind.

High Gravity vs. Target Strength

Hard seltzer begins with water and sugar—typically sucrose, sometimes dextrose. Among the first choices is whether to ferment this neutral base (or sugar wash) to working strength at the outset or brew it to a higher gravity and then dilute it down.


For example: The team at Night Shift in Boston (see our Case Study, page 58) found that they liked the product better when they used wine yeast to ferment the base to the target strength—no dilution necessary. Colby says that many smaller brewpubs have been doing the same. One advantage of this method: The fermented sugar wash winds up with fewer undesirable esters.

However, the bigger commercial breweries—and even many smaller ones following their model—tend to brew higher-gravity solutions and dilute them. How many tanks a brewery has available is likely to affect this choice.

Colby explains, “They’re going to want to brew something so that when they dilute it down, it dilutes to an even number of tanks for them,” he says. A hypothetical example: “If they have two five-barrel tanks and then one five-barrel fermentor, they’re going to want to make a 10-percent ABV solution, so they can fill those two at 5 percent, if that’s what they’re making.”

Breweries might aim for gravities as high as 18–22 Brix (1.074–1.092), Colby says, or “as high of a gravity sugar wash as they can get away with and fits in their brewery.”

Fermenting the Sugar Wash

Water is important, given that we’re essentially talking about flavored booze-water. On the other hand, the water chemistry is less important than it is with beer, where there are myriad considerations related to the mash, hop profile, and target style. Colby says that if your water is free of chlorine and tastes good, then you’re 90 percent of the way there.


As with beer, you want a healthy, predictable fermentation—and one that doesn’t take longer than it needs to. That means finding the right yeast and plenty of nutrient, including yeast hulls and nitrogen—between 250 and 300 parts per million (ppm) of the latter, according to Colby. The source of nitrogen might be urea or diammonium phosphate (DAP).

What many brewers do, for the sake of simplicity and to avoid cross-contamination, is first try their house brewing yeast to see whether it will do the job well enough. It usually will, Colby says, but it takes some tinkering. “There’s a fairly large swath of yeast strains from the whole spectrum that do pretty good, under the right circumstances,” he says. “I mean, you need to mess with the pitching rate, you need to vary your aeration, you have to try different yeast nutrients.”

Colby has heard from some brewers who tried to brew production-size batches out of the gate and had problems with fermentation. “And one thing I highly recommend in the book is to brew some pilot batches,” he says. “Even if you have to go out and buy a simple homebrewing kit and do it at a five-gallon scale, get something [in the] ballpark first. And then if you have a small pilot system that’s a couple of barrels or something, get it to work there before you jump to your 30-, 40-barrel system, because people have a lot of trouble getting these fermentations to go.”

Even after the product is on the shelf, tinkering with the fermentation can be an ongoing project. “If you can tweak it so the fermentation finishes a day earlier than it normally does,” Colby says, “that’s money in the bank.”

As usual, temperature control is key. Fermenting too warm with most yeasts is likely to produce undesirable esters. One shortcut is to use distiller’s yeast, which can come packaged with all the needed nutrients. “So that’s an easy route, if you don’t want to use your own yeast and do all the fine tuning,” Colby says. “Some of these distiller’s yeasts are meant to be pitched into just sugar and to do the job.”


In case of stuck fermentations, some of the remedies will be familiar: You can try rousing the yeast, raising the temperature, pitching some actively fermenting sugar wash (a bit like kräusen), or adding more nutrients—but not too late in the process because if they survive the cleanup process, they might end up as food for unwanted contaminants.

Watching the pH level is important, too. It should start at about 5, but it will drop during fermentation. The yeast will struggle if the pH drops below about 3.5, Colby says. Adding some sodium bicarbonate (baking soda) can help absorb some acids and raise the pH—but not too much. “You don’t want to zip it all the way back up to 5 because you want it to finish,” he says. “It should finish at a fairly low pH because most of these are canned at a pH of about 3.1—[so] they’re not sour, but they’ve got a little bit of zing or whatever, or there’s a crispness to them. That comes from having a fairly low pH.”


Photo: Matt Graves/


After fermentation, the solution needs to be stripped of all undesirable aromas, tastes, and (usually) colors. Bigger commercial breweries tend to use membrane filtration to achieve this, via nanofiltration and reverse osmosis.

In Waunakee, Wisconsin, the contract brewery Octopi produces the Florida range of hard seltzers for Levi Funk’s Untitled Art brands (highly regarded by our editors and high-scoring among Untappd users). Funk, who also founded the Funk Factory Geuzeria, says it’s important to first produce a clean, clear base seltzer. He says that at Octopi they have a “very expensive piece of machinery”—a high-pressure membrane filtration plant—used to strip the sugar wash of all flavors and aromas. Generally, that equipment is within the reach of only larger breweries.

Mid-sized breweries typically have a different set of options, such as plate filtration and activated carbon. With plate filters, Colby says, “the thickness of the carbon filter is going to determine how much character gets scrubbed out of a sugar wash. You’re shooting to remove any off-odor, any off-color, and any flavor.”


“The recommendation I would have for smaller brewers is first, getting that base seltzer as clean and clear as possible,” Funk says. “Then, I would say it is our duty as craft-beverage producers to look at this as a new base and our responsibility to then create a craft version of hard seltzer.”

On the smaller scale—especially if the solution was fermented to working strength, where esters will be less of an issue—finings should be enough to get the job done, Colby says. The fining agent PVPP (polyvinylpolypyrrolidone)—such as the brand Polyclar VT—is widely available from suppliers. Following that up with activated carbon is an option (if the crew has time to deal with the dark sludgy mess that results). Another possibility, Colby says, is to recirculate through a grant with a bed of activated carbon.

On any scale, if any off-odors persist, Colby says that bubbling some CO2 up through the solution can do the trick via off-gassing.

Adding Flavor & Bubbles

That neutral base, in essence, is a blank canvas on which a brewer can work creatively to produce something distinctive—and, ideally, delicious.

“There is an endless opportunity to explore with this base, and what that looks like will be up to the individual producer,” says Funk. His Florida hard seltzers, for example, get fruit purees and juice concentrates. Varieties include Black Cherry, Blood Orange & Pomegranate, Pineapple Mango, and Prickly Pear & Guava.


Big commercial breweries tend to rely on flavor extracts, whose contents are predictable and carefully listed to help brewers comply with any FDA or TTB regulations. Often these products include ethanol; brewers need to account for that when they calculate ABV.

When it comes to adding more natural (and less predictable) ingredients, there is a whole spectrum of options and risks to consider—fermentable sugars, possible contaminants, solids in suspension, and color, to name a few.

In Stratford, Connecticut, Two Roads has followed, well, the road less traveled. Its H2ROADS line of hard seltzers debuted in late 2019 with three flavors: Cranberry Lime, Grapefruit, and Raspberry.

One thing that makes H2ROADS different is the use of 100 percent real fruit. Phil Markowski, cofounder and brewmaster, says they knew they wanted to avoid any artificial flavorings or additives.

Rather than going for a totally colorless product, they embrace color. “The product retains the color of the fruit, which is a point of difference that we absolutely want,” he says. “Our product is designed to be an alternative to the [colorless], artificial-tasting hard seltzers that currently dominate the market.”


They add the fruit after fermentation, then use a centrifuge to remove any solids because the fruit leaves behind some fermentable sugar, “which can alter the flavor and character of the product over time,” Markowski says. It can also affect ABV and carbonation.

“Our ‘secret weapon’ is a tunnel pasteurizer—a piece of equipment that is bulky and expensive but really the only way to stabilize a product like this without using chemical preservatives,” he says. “Again, our mission is to produce a 100 percent natural hard seltzer for consumers [who] want real fruit, real flavor, and nothing processed or artificial.”

Generally, hard seltzers are fruit-flavored, with the occasional complementary herb or spice. One way to accentuate those fruit flavors is to punch up the acidity. Considering that many of the flavors are citrus-centric, Colby says, “adding a little more citric acid sharpens up the little flavor that you do have.” With other fruits, such as cherries or peaches, adding malic acid can kick up a Granny Smith–like bite and brighten the flavor.

Such acids can also help bring the pH down to a safer 3.1 or so. “At that level, you’ve reached a level of biological stability,” Colby says. “Few contaminants are going to be able to live in a 4 or 5 percent ethanol solution with a pH of 3.1.”

As for the fizz: Commercially available canned seltzers are typically carbonated to about 2.8 volumes—they should have some zip to them.

For his part, Funk encourages his fellow brewers to challenge themselves and go beyond the usual flavor extracts to make something distinctive. “That is a very simple product and easy to replicate, but I don’t believe replicating those products represents the craft-brewing spirit,” he says.

Craft brewers, he says, “are a creative bunch, and I’m looking forward to seeing how others use their creativity on this new base, just as we have with every other style of beer.”

Joe Stange is Managing Editor of Craft Beer & Brewing Magazine® and the Brewing Industry Guide®. Have story tips or suggestions? Contact him at [email protected].