We can all picture a day when we’ve experienced all of the highs. You’ve come up with the best idea for a beer — a clever showcase for a new flavor or ingredient, a new hop combination heretofore unknown to brewer kind. You’ve sweated with mash and boil-powered steam facials. The beer was cooled, the yeast was sent to its pool party, beers were cracked, and everything is going great. The party in the fermenter raged with all the fervor of the best EDM fueled raves – until it didn’t. 

Something happened — the quiet hi-hat “clink-clink-clink” of the airlock has unexpectedly stopped. Did the fermentation police bust up the festivities? Did everyone drop from exhaustion before the last bass drop? Did everyone scatter before the cleanup could finish? For whatever reason, the fermentation stopped dead in its tracks and you want to know what to do! We’ve all been there and like the best party planners, we have the tools to clear up the mess and close out your fermentation on a high note.

That’s the subject of today’s column —restarting a stuck fermentation. Though, before we go through the efforts of kicking fermentation back into gear, we must first determine if it truly stopped prematurely. 

Verify The Facts at Hand

Before allowing panic to set in, make sure of your supposition. Did the fermentation truly quit early? 

Start by asking yourself some basic questions. How many days have you been fermenting? With healthy yeast (remember our repeated mantra — healthy, vital yeast forgives many sins) a normal gravity beer (1.040-1.055) can be done with active fermentation in 2–3 days post pitch. A session beer even quicker, a large beer may take over a week to quit showing obvious signs of fermentation, and all bets are off if you throw a kveik strain at it. (We discount fermentations that are rumored to finish before they even begin as we respect the fundamental laws of physics in this brewhouse.)

The next question, is fermentation truly stalled? Most homebrewers will look to their airlock or blow-off tube and those reassuring tiny bubbles to tell them that things are progressing. The seemingly sudden cessation of emissions has sent many into a tizzy, but while gas evolution is an easy gauge of fermentation, it is not always accurate. 

So first, check your airlock. Is it seated firmly and correctly? Is the lid on correctly and closed tight? Given that gas can easily slip through the eye of a needle and will take the path of least resistance, even the most insignificant seeming gaps will still an airlock. Is anything blocking the potential outflow of gas? We’ve caught bucket lids bulging like the nascent Yellowstone Caldera because gunk sealed our airlocks inside the chamber. (Caution is highly recommended when removing that airlock. You might just paint your ceiling.)

Assuming the hatches are battened down and everything should be flowing, your next quick observation to make is whether there is a lovely foam cap of kräusen still swimming in the fermenter? This is where clear carboys are such a benefit as you can see exactly what’s going on inside your fermenter without disrupting anything. If you ferment in a bucket or shiny stainless steel fermenter, you’ll have to open it up to take a peek. Quick, close it! If there’s a cap, be patient and come back a few days later. If not . . . then we measure!

Take a gravity sample. Make sure to properly de-gas the sample lest any stray bubbles buoy your hydrometer and give you an artificially high reading. While some recommend giving it a spin in a blender, a few passes back and forth between glasses should suffice. Measure the gravity. Is it in a reasonable range of where you’d expect it to be? The usual rule of thumb for final gravity is to have it somewhere equal to or lower than a quarter of the original gravity. For our hypothetical “normal” beer of 1.050, we’d expect the gravity — for most yeast strains — to be around 1.012–1.013, or lower (50/4 = 12.5). If your gravity is a little higher, say 1.014–1.016, give the sample a taste. Odds are good that the beer will taste fine and is suitably done. Give it a few more days and then keg or bottle.

As an aside, it would take better beer judges than us to detect that difference from a beer we’re unfamiliar with. As an aside to the aside, one of the things that separates homebrew from commercial brews is where those final gravities land. It’s not uncommon to hear professionals mention that their beers finish a few points lower — 1.004 to 1.008, for instance. Something to think about and then forget as long as you enjoy your beer!

If the gravity isn’t in range, wait a few days more and measure again. Has the gravity moved? If so, great! You’re not dead yet, just moving like dancers towards the end of an old-fashioned dance marathon. 

Fixing a sluggish ferment starts with an environment check — is our fermenter too cold? Temperature ranges aren’t instant light switches (“Get this below 60 °F/16 °C and it’s night night!”). They’ll continue to work, just more slowly. Slowly raise the temperature and see if you get further fermentation. Don’t be fooled by a temporary bump in bubbling. As the beer warms, CO₂ will come out of solution due to the fact that less gas will dissolve in a warmer solution (Henry’s Law!).

Our anti-sluggard action continues with the brewing equivalent of a good brisk walk to wake back up. Give the fermenter a light bit of agitation — a swirl of the bucket, a bubble of CO₂ through the keg or conical — with the aim of putting yeast back into solution and thus back to work. Again, gas will bubble out of the airlock because you’ve knocked it out, so wait and see if fermentation resumes.

If neither of these actions work, or your test gravity samples didn’t move and are pretty far off (and agitating didn’t help there), then it’s time to call in the reinforcements to get the dance floor packed again. It’s time for the REPITCH REMIX.

All you need is a healthy dose of pretty much any neutral-adjacent ale yeast. We keep dried yeast on hand — a pack of a yeast like SafAle US-05, LalBrew BRY-97, LalBrew CBC-1, or a kveik strain will do the trick every day. No dried yeast? A small (1⁄2 cup) slug of yeast slurry from another batch of beer or even a freshly made starter at kräusen will suffice. We don’t recommend using a characterful yeast (say a Belgian strain) just to avoid the tiny contribution it will make to the final flavor. While you may see it recommended in online forums and other places, we also really, really don’t recommend wine or Champagne yeast. They have their own characters (and impacts on other yeast strains) and despite their high alcohol tolerances, they prefer to ferment simpler sugars than some of the more complex sugars found in beer.

With the extra yeast secured, add it to the beer, keep the fermenter at the upper end of your fermentation temperature, and wait a week. If all goes to plan, then this clean-up crew will bring your gravity down to your desired level. If not, try giving it another swirl and letting it go. Don’t add any oxygen when you do these late pitches to avoid damaging the beer!

The Party Is Still Dead

When not even a whole new dance crew can shake the fermentation back to life, and you’ve considered that the pros and cons of leaving the beer be and packaging as is leaves you with too many cons, then it’s time to consider the big guns. We cannot stress enough that these levels of interventions should be considered only when the beer would be a total loss otherwise. Taste and think, taste and think!

First, everyone recommends it, but we honestly don’t know that many people who’ve done it — brew another batch of beer! The theory goes that making a second, lower-gravity beer will allow you to blend and dilute the gravity. It’s a lot of work for an uncertain impact. 

Instead, we’d recommend diluting with water or even booze to drop the perceived final gravity. Mike “Tasty” McDole used to thin out a stronger beer with de-aerated carbonated water to make “golfing beer.” There’s no reason you can’t use the trick to make a lower final gravity. We have also used strategic additions of whiskey or schnapps to reach a lower apparent gravity (or in Drew’s case, to add a fruit flavor that is reinforced by the residual beer sweetness). If going this route, do some trials first before blindly pouring a bottle of booze into your fermenter. 

Thinking further outside the box, another option is to reach for a cold-acting amylase enzyme (ala Beano). Enzyme additions do not correct failed fermentation, but they change wort fermentability. A small dose of the enzyme will attack the long chain sugars that are probably preventing your beer’s final fermentation. Monitor your gravity and ensure your yeast is healthy and cleaning up after itself. A fair bit of warning though — once added, you cannot stop the process — the enzyme will continue to convert sugars. As people discovered in the brut IPA era, cold enzyme additions can lead to diacetyl butter bombs from yeasts that have not finished fermenting. If you anticipate a challenging beer fermentation from the start, you could always add an enzyme like White Lab’s Ultra-Ferm® to the mash and then denature it during the boil. 

A couple of other ideas include trying a diastatic yeast (STA-1 positive) or even relying on hop creep to further dry out a beer that won’t ferment as low as you want. Read more about these options in the “Related Links” at the end of this article.

If even these tricks won’t solve the issue, you may consider this brew a life lesson that teaches as it circles the drain. Learning from mistakes is a part of the hobby.

Party Postmortem

No matter the outcome, you should take a moment after the chaos fades to figure out why things went so squirrelly. There are various factors that can lead to a stalled fermentation, and getting to the bottom of the cause can help prevent it from happening again. Stop and ask yourself:

• Was your yeast truly healthy and raring to go? 

• Was the yeast strain used suitable for the alcohol level of your beer?

• Did your malt bill get stuffed with large doses of complex specialty malts? 

• Was your mash converting all of your starch into sugar? Did your temperatures favor more long chain sugar creation (high) or maybe the enzymes couldn’t reach starch trapped in mash pockets?

• Did your water have 25+ ppm of calcium? 

• Was your final boil pH too low or too high? 

• Were there sufficient nutrients to power yeast replication? (Unless you’re doing something spectacularly adjunct heavy, you had enough.) 

• At pitch time, what was the wort temperature?

• Were your fermentation temperatures out of whack (too high or too low)?

• If you track fermentation gravity, did something occur around the time of “the stall?” 

Look for the odd ducks, the differences, and maybe you can isolate the cause of your dilemma, because we all know that preventing a problem is better than fixing it! 

Dip hopping originated in Japan but is becoming increasingly popular in North America. Learn more how to use this technique in your Nano brewery to boost pleasant hop aromas while suppressing or removing unpleasant off-flavors, like myrcene, and aromas that are derived from fermentation.

PDF of Presentation Slides: https://byo.com/wp-content/uploads/Ashton_Lewis_Nanocon_2025_Dip-Hopping-2.pdf

Although the first hydrometer was described more than 1,600 years ago, its use in brewing dates only to the late 1700s. More than 250 years of data collection show that beer strength has historically been moderate by modern standards. Strong beer styles intended for storage, shipment, or sipping at higher alcohol levels are the obvious exceptions. Even today, most beers remain within a moderate range when compared to other alcoholic beverages.

Brewing history also shows that malted grains were the dominant ingredient in beer until the late 1800s, when German-American brewers began using corn (maize) and rice adjuncts to dilute malt protein and husky tannins from Midwest barley varieties of the time. Contrary to popular belief, adjunct use aimed to improve beer quality, not to reduce production costs.

You may be wondering: What do wort gravity, beer strength, and adjunct use have to do with yeast nutrition? These historical details reveal that brewers have been fermenting normal-gravity, high-malt worts for centuries. They also suggest that beer has been popular enough to sustain a continuous brewing tradition for thousands of years without the use of yeast nutrients until quite recently.

The modern biochemical argument for the rise of yeast nutrients is rooted in our growing knowledge of zymurgy. Without that scientific framework, how could brewers have known when or how to supplement fermentation? And yet, they developed the complex triple decoction mash — without any understanding of enzymes and without thermometers — crafting a reliable process from inconsistent, poorly modified malts.

The more practical explanation for the recent widespread use of yeast nutrients is simple: They weren’t necessary for brewing the kinds of beers that dominated most of brewing history. So why are yeast nutrients now ubiquitous among both home and commercial brewers? Before exploring that question, let’s review how nutrients are used by our fungal friends.

Zinc is a critical cofactor for alcohol dehydrogenase, the enzyme that converts acetaldehyde to ethanol. It also supports yeast cell membrane integrity. Adequate zinc levels promote faster fermentation, better attenuation, and cleaner-tasting beer. Because wort is often zinc-deficient, supplementation in the range of 0.1–0.3 ppm can be beneficial. Although many references, often without citation, state that excess zinc is toxic to yeast, this concern is usually overstated. Problems typically arise when the zinc concentration is around 3 ppm or greater, roughly ten times the upper limit of normal additions.¹

B vitamins (including thiamine, riboflavin, niacin, pantothenic acid, biotin, and folic acid) act as coenzymes in glucose metabolism, energy production, and fatty acid synthesis. They are essential for yeast growth, reproduction, and complete attenuation. Most are present in sufficient quantities in wort, though high-adjunct worts may be deficient.

Amino acids (organic nitrogen from raw materials) and diammonium phosphate (DAP, an inorganic nitrogen from nutrient supplements) supply yeast with nitrogen for protein, enzyme, and structural component synthesis. Both forms promote faster yeast growth and more vigorous fermentation.

Nitrogen in wort is measured as free amino nitrogen (FAN) and comes primarily from malt and, to a lesser extent, from protein-rich adjuncts, except when DAP is added directly as a nutrient. Because proline is a major component of FAN but is not assimilated by yeast, a wort with high FAN can still lack certain essential amino acids.

Magnesium stabilizes metabolic enzymes, is critical for ATP production, and helps regulate intracellular pH during fermentation. It improves yeast vitality, enhances stress resistance, and supports consistent fermentation performance. Malt typically provides sufficient magnesium.

Manganese serves as a cofactor for antioxidant enzymes such as superoxide dismutase and plays a role in carbohydrate metabolism. It protects yeast from oxidative damage and supports cell health throughout fermentation. Malt usually supplies enough manganese.

Phosphorus is essential for ATP formation, phospholipid synthesis, and nucleic acid production. Malt is a rich source of phosphorus.

Potassium boosts metabolic enzyme activity and helps regulate intracellular pH and osmotic pressure. Malt typically contains sufficient potassium.

Calcium stabilizes yeast cell walls, aids flocculation, and influences enzyme activity. It can improve beer clarity but, in excess, may slow yeast growth. Mash additions for pH control and alpha-amylase stabilization typically meet fermentation needs.

Sulfur, usually in the form of sulfate, is required for the synthesis of sulfur-containing amino acids such as methionine and cysteine, as well as certain vitamins. Wort sulfate comes primarily from brewing water, as malt and other carbohydrate sources contribute very little. Many nutrient blends supply sulfate via salts such as zinc sulfate, magnesium sulfate, manganese sulfate, and potassium sulfate.

Lipids and sterols are necessary for maintaining yeast cell membrane fluidity and function. They improve ethanol tolerance, ensure complete fermentation, and enhance yeast vitality in harvested crops. Although wort contains little lipids or sterols, yeast can synthesize them if sufficient oxygen is available. Dried yeast typically contains ample lipids and sterols, eliminating the need for wort oxygenation.

In short, all-malt wort is almost the perfect source of everything a yeast cell needs to thrive. The one exception is zinc, which is often deficient. Unless you strictly follow the Reinheitsgebot, many options exist to correct zinc deficiency. If the Reinheitsgebot is your jam, consider biological acidification using spent grains as a zinc source (much of the malt zinc leaves the brewhouse with spent grains) or Servomyces. Because few homebrewers strictly adhere to the Reinheitsgebot, I’ll avoid the rabbit hole on the horizon!

So why are nutrients commonly used if all-malt wort is so nutrient-rich? The most common reason is dilution of malt-derived nutrients by unmalted adjuncts such as corn/maize and rice. Because malts from most regions are now well-modified and often contain excess nutrients, dilution is generally not an issue until adjunct levels exceed about 20%.

Another common use, especially in commercial brewing, is in high-gravity brewing, where high-alcohol beer is diluted with brewing water after fermentation. Home and craft brewers face similar challenges when brewing big beers, with or without sugar adjuncts. These strong worts cause greater osmotic stress on yeast at fermentation onset and more ethanol stress as fermentation progresses. Nutrients help improve metabolic efficiency and enable yeast to synthesize membrane components that cope with these harsher conditions.

Finally, there is hard seltzer — the beverage that has opened many brewers’ eyes to the importance of yeast nutrients. Proper nutrient additions allow yeast to quickly and cleanly ferment “worts” made entirely from glucose (dextrose or corn sugar), sucrose (cane or beet sugar), and/or fructose (fruit sugar).

The underlying commonality of these cases is speed and reliability. When nutrients are added to deficient worts, fermentation is faster, cleaner, more consistent, and generally less stressful for brewers hoping that a fermentation makes it to the finish line and tastes as expected after the long wait.

Now that we’ve covered some background and identified the beer styles most likely to benefit from nutrient additions, the obvious question is: How much should I use? Unfortunately, that’s not an easy one to answer. Brewers often use FAN as a nutritional metric because it measures the pool of amino acids and small peptides in wort that yeast can readily assimilate for protein and enzyme synthesis. While FAN is useful for gauging nitrogen availability, it tells only part of the story. Yeast also requires vitamins, minerals, lipids, and other cofactors for optimal health. FAN measurements do not capture these other essential nutrients or account for amino acid imbalances. Because most brewers are not equipped to analyze a wort’s complete nutrient profile, they rely on general guidelines and trial-and-error adjustments to determine dosage rates. Table 1 offers guidance on which nutrients to consider for different wort types.

If you’ve read about nutrients in winemaking or cidermaking, you may already be familiar with YAN (Yeast Assimilable Nitrogen) and wonder how it differs from FAN. YAN measures all amino acids except proline, along with ammonia — the form of nitrogen supplied by DAP and urea (the latter not discussed earlier since it is rarely used in brewing). While YAN is a more complete metric than FAN, maltsters and brewers generally do not measure it because two separate analyses are required.

This seems like a logical point to introduce the nutrients available to homebrewers and show how they fit into the framework outlined earlier. The challenge is that while there are many products available to the brewer, most provide limited technical detail about their actual composition. Suppliers tend to sell performance while treating formulation as proprietary. Still, ingredient lists can offer valuable clues.

For example, products without zinc should be assumed to contain no zinc unless the nutrient is specifically marketed as a zinc source, such as Servomyces. Those containing yeast extract or yeast cells provide organic nitrogen along with B-vitamins and micronutrients. Soy flour also supplies organic nitrogen. Nutrients made with DAP or urea (more common in distilling or very high-alcohol fermentations than in brewing) deliver inorganic nitrogen. Some labels simply mention “trace minerals,” while others list specific salts such as magnesium sulfate, manganese sulfate, or potassium sulfate. The real difficulty lies in knowing how much of each nutrient is delivered at the recommended dosage — an area where comparing notes with fellow brewers can be especially helpful.

In summary, yeast nutrients have become important not because traditional malt worts were lacking, but because modern brewing practices often create new stresses for yeast, including shorter fermentation windows. High-gravity fermentations, heavy adjunct use, and sugar-based beverages like seltzer reduce nutrient availability and increase fermentation challenges. Supplements such as zinc, amino acids, vitamins, and trace minerals help maintain yeast vitality, improve stress tolerance, and support clean, consistent attenuation. By recognizing when supplementation is most beneficial, brewers can adapt to today’s diverse styles while ensuring fermentation reliability. Thoughtful nutrient use ultimately strengthens yeast performance and enhances the quality of the finished beverage. 

References:

¹ Yun-ying Zhao, Chun-lei Cao, Ying-li Liu, Jing Wang, Jie Li, Shi-yun Li, Yu Deng, Identification of the Genetic Requirements for Zinc Tolerance and Toxicity in Saccharomyces cerevisiae, G3 Genes|Genomes|Genetics, Volume 10, Issue 2, 1 February 2020, Pages 479–488.

Q: How does lagering a beer in a carboy or barrel affect the beer differently than storing the same unfiltered beer in a bottle or keg at the same temperature for the same period of time? 
— Chris Patterson • Downers Grove, Illinois

Mr. Wizard says…

A: This is a great question, Chris, and the answer starts with a quick review of the objectives of lagering. Although lagering is most often associated with lager beer, the process can be applied to all types of beer. Some brewers refer to all aging processes as “lagering,” others use the term “cellaring,” and some simply say “aging.” Naming aside, yeast sedimentation, diacetyl and acetaldehyde reduction, flavor integration, and sulfur scrubbing are among the key changes in beer flavor and appearance that can occur during lagering. In the commercial lager world, lagering may also include partial or complete natural carbonation.

Cask conditioning, while rooted in ale tradition, shares much in common with lagering. One of the key differences between lagering and cask conditioning is volume: Lagering is a bulk process in which the finished beer is later transferred to kegs, bottles, or cans, while cask ales are conditioned in the very vessels from which they are served. Another difference is yeast sediment. Commercially packaged lagers typically do not contain yeast sediment, whereas cask ales generally do.

At home, lagering can be done in containers that do not permit carbonation, such as carboys, or in containers that do, such as kegs or certain pressure-rated small fermenters (such as those included in this homebrew unitank comparison). In both cases, beer clarification, flavor maturation, and sulfur volatilization occur. Lagering in a keg allows homebrewers to mimic commercial practices, including kräusening — adding actively fermenting beer to fully fermented beer to achieve carbonation and speed aging. A key part of this process is venting excess gas. While aging in a carboy also allows sulfur venting, keg aging, where CO₂ is naturally produced and released, is my preferred method.

When lagers are aged in bottles, three important things cannot occur: Sulfur scrubbing, yeast sedimentation, and yeast separation. A practical solution for home lager production is to select a yeast strain that produces clean, low-sulfur lagers within a short fermentation and maturation window. Strains such as SafLager W-34/70 can be used successfully at warmer temperatures (59–68 °F / 15–20 °C) by both home and commercial brewers to quickly produce beers with low diacetyl and sulfur. Others, such as LalBrew NovaLager, have been developed through traditional selection and hybridization to yield strains that produce minimal diacetyl and hydrogen sulfide. 

As long as the beer is cooled to encourage most yeast to drop out before packaging, you can bottle-condition and age for flavor integration. Is the result identical to bulk-aged lager? Probably not, but it can be surprisingly close.

There are many kinds of brewers, from extract brewers making their beer in five-gallon (19 L) buckets to commercial brewers making their beer in multi-story fermenters. The skills these brewers need and the procedures they use vary substantially. However, there are two skills that every brewer needs, no matter what size brewery they brew in: cleaning and sanitizing.

Cleaning and sanitizing your brewing equipment is the first step listed in the procedure on brew day. Your brewing equipment needs to be as clean and as free from biological growth as possible. The only organism you want growing in your fermenter is yeast. Growth of other organisms in unfermented beer (called wort) can spoil the resulting beer. Contaminated beer may turn out sour or develop other off flavors and aromas. In addition, the beer may overcarbonate and gush when opened. In extreme cases, your bottles may explode.

Learn the keys to running a good homebrew fermentation from adding enough yeast to keeping the right temperatures to help your beer be the best it can be. Learn the basics with the help of Brew Your Own’s Technical Editor Ashton Lewis.

One of the essential skills you will come across when homebrewing is racking or siphoning. This is when beer is moved from one container to another to separate it from the particles that settle at the bottom of the carboy, fermenter or bucket. Learn this skill in this video.

I monitor my fermentation with a Tilt hydrometer, but back it up with a standard hydrometer. The two are always a little off but are good checks. My final gravity (FG) is always high, no matter what style I am brewing. If the target is 1.018, I’m usually finishing at 1.022. Although I calibrated my Tilt, the hydrometer reads 2–4 gravity points higher for final gravity even when adjusted for temperature. What am I doing wrong to always have higher gravity at the end of fermentation?
— Barney Heller • North Wales, Pennsylvania 

A: Well, Barney, this question touches on two separate pain points in brewing — measurement challenges (calibration) and final gravity issues.

One of my brewing touchstones is to always give instruments a serious side-eye. I don’t recall when I began questioning instruments, but know that mistrust is an asset. You have two instruments that are supposed to measure the same thing and have two different results. You have two options: Compare your Tilt and your hydrometer against standards (and when you say you calibrated the TIlt hydrometer, I’m guessing this is what you have already done) or add a third instrument to the party. Although the second option is not a terrible idea, unless the third instrument has been certified all you will do is add more confusion to things. So, what about bumping these up against a standard?

The gold standard for specific gravity is pure water with a density of 1.000 kg/L or a specific gravity of 1.000 (SG is unitless as it compares the density of one liquid to that of water). For many instruments, a single-point calibration is insufficient and a second or third calibration standard is required. Examples of multi-point calibrations include pH, temperature, and mass. This is also true of density, but once a hydrometer of a given length and weight is calibrated over a range using at least two calibration standards, the calibrated scale can be replicated. The takeaway is that you have completed the first step in sleuthing out the measurement by dropping your hydrometer and your Tilt into pure water and measuring the density. They both should read 1.000 at the water temperature your hydrometer is calibrated (your Tilt has a built-in correction).

My distrust of instruments is generally related to devices with “black boxes” that bring in some sort of input and return a value. Measurement errors often result from something awry with the black box input. This could be a dirty sensor, something touching a sensor, or interference with moving parts. The Tilt is a clever device where density is determined by the angle that the Tilt device floats in liquid. As density drops, so does the Tilt device. And as the Tilt hydrometer sinks, it becomes more vertical. Drop the same Tilt hydrometer into a high-gravity wort, and it will lean more horizontal.

Both of your devices have simple measuring principles, although the inner workings of the Tilt are nifty. And both devices will be affected by deposits on the surface that change the weight of the device; make sure they are both clean. My money is on the Tilt for being correct and your hydrometer for being off. I guess this is a good time to mention that you are probably not the problem.

Hydrometers rely on the proper placement of a slip of paper for proper calibration. Misplacement by a couple of millimeters in a short hydrometer can result in significant errors. This is why it is critical to always test hydrometers in standard solutions. For those of us using sets of tall hydrometers with relatively narrow ranges, for example 1.000–1.034 SG, 1.032–1.068 SG, and 1.065–1.101 SG (or 0–8.5 °P, 8–16.5 °P, and 16–24 °P), calibration is easier said than done. Suffice to say, don’t trust a hydrometer further than you can drop it before first checking it out.

Missing your FG is a deep topic that I will simply dip my toe into. For starters, the FG of a brew has a lot to do with malt, mashing, and yeast. Change any of these things and expect a change in FG. But then there is the published FG. What does this mean? Is it a value plucked from the performance of a single batch of beer or is it the average FG of many, many brews of the same recipe? Here is the thing with FG . . . it usually contributes less to body and flavor than brewers think. The one exception to this is when a beer finishes high because of unfermented sugars that are sweet.

Details aside, if you want a drier beer, there are a few easy things to try. The first is extending your mash temperature in the 149 °F (65 °C) range. Sixty minutes is long enough to produce highly fermentable wort. Another thing to consider is to back off specialty malt additions, like crystal and caramel malts, that boost FG. And then there is yeast strain; yeast strains that are either unable to ferment maltotriose or those that do so poorly will leave higher finish gravities compared to strains that do ferment maltotriose. For the latter, most lager strains and ale strains like Chico gobble up maltotriose like nobody’s business.

In the world of beer, time spent in the fermenter and energy spent keeping things cold is money — making lagers particularly expensive to age. After all, we all know that lagering takes 40-plus days at near-freezing temperatures to make true and proper crystal-clear Pilsners and the like. 

You can imagine, then, that commercial breweries have every incentive to cut the amount of time and energy needed to make a beer. Brewing profit margins are slim when you’re at the scale of beer pricing wars, so any penny saved is a penny back into the company coffers. It’s that expediency that has driven much of the research in lager processes and ingredients. From time to time, you’ll see news announcements about lager breakthroughs — new yeast strains that require less chilling, ceramic plates infused with stabilized yeast that can, in theory, ferment a lager lickety split. And if you’ve been paying attention to the homebrew gear market, you may be able to guess where we’re going with this: Pressurized fermentation. 

One of the best things about homebrewing is that we sit at a swirling nexus of possibilities. Each of us can choose from a thousand ways of brewing and various levels of “tradition” vs. “technology” and this split is perfectly represented by the technique of pressure fermentation.

Here’s the basic theory: Warmer fermentations create more flavor compounds and in turn require more time to mellow. It’s a well understood fact that pressure during fermentation reduces ester formation regardless of the temperature. With fewer esters (and other flavor compounds) being produced, there’s less cleanup work needed.

We see this in the big tanks used by commercial brewers, and hence the reason we always caution that if a pro brewer says they ferment at 72 °F (22 °C), homebrewers should usually knock off a couple of degrees to adjust for the fact that our 5-gallon (19-L) columns of liquid just don’t have the same resulting pressure suppression that even a 200-gallon (760-L) batch self-generates. 

Pressure fermentation takes that character suppression a step further. Rather than depend on the native pressure generated by our batch sizes and fermenter geometry, why not turn to a long-lived piece of brewing equipment — the spunding valve?  You know it’s good for brewing because its name has a German origin (from spund in German meaning “bung” — aka how you’d seal a barrel of beer). 

Unlike an actual hard bung, the spunding valve is a selectable pressure relief valve (PRV). You select a specific pressure (say, 14–15 PSI) and the valve allows that much pressure to build inside your vessel before venting to avoid over pressuring. These valves are widely used in commercial brewing, particularly at the tail end of fermentation (more on that later).

It wasn’t that long ago that if you wanted a spunding valve for home use, you had to build one for yourself. (Drew still has a homemade one full of automotive parts and enough Teflon tape to plumb a house sitting in his brewing toolbox.) These days you can buy any number of fermenter-specific or generic valves from homebrew suppliers. They have decidedly less Teflon tape!

When combined with an appropriate fermentation vessel, the spunding valve means you now have a pressure environment in your brewery in addition to your kegs. Let’s be very clear about that appropriate bit. By and large, general plastic vessels and all glass carboys are not appropriate vessels. 

We’re going to repeat that for the folks goofing off by the fermenters in the back — don’t pressurize containers that aren’t meant to hold pressure. We have very few hard-set rules, but that’s a good one to have. No one needs to lose an eye because they’re making beer. 

Don’t be fooled by the materials either — a good number of stainless-steel vessels are not meant to be pressurized. We both use Grainfather GF30 Conicals in the brewhouse; despite being lovely gleaming stainless steel, they are designed to release their lid if the pressure inside gets above ~3-5 PSI (this is to prevent the device from becoming an accidental 30-L pipe bomb). 

There are other conicals and even plastic fermentation systems that allow you, with accessories and care, to pressurize your fermenter. Each system works a little differently, but the basic rules are the same. We’ve both used Corny kegs to do our pressure tests.

So, let’s determine how you want to “pressure ferment.”

The most common use of pressure fermentation is to cap the vessel towards the end of fermentation to capture CO₂ and begin carbonating the beer naturally.  

• Choose a target gravity to begin capping. Usually when you have about 4–8 gravity points (1–2 °P) left in fermentation. For instance, if you have a beer you expect to finish at 1.010 SG, you’ll want to cap between 1.014–1.018.

• Attach the spunding valve to your fermenter as directed (in our case, it was as simple as attaching the spunding valve on a keg gas fitting and plugging on the gas post).

• Dial in your specific desired pressure (14–18 PSI is common for carbonation).

• Let the beer finish and transfer under pressure to a waiting keg.

• Check the carbonation and serve when ready.

For the full-on pressure fermentation with the beer always operating under pressure, the process is much the same — except you attach the spunding valve from the start and go from there. 

A few rules of thumb:

• What pressure and what temperature you use in fermenting is going to be largely strain-dependent. Some yeast strains produce solid and reliable results while others are much less effective working under serious pressure. Any of the 34/70 family of strains appear to perform like the global workhorse they are proclaimed to be. Drew has also used SafLager S-189 with positive results (a good place to start is around 13–15 PSI). There are several strains sold as “pressure fermenters,” but you can achieve the same results with trial and error with regular yeast strains. Keep in mind that until you gain experience with this technique, you’re bound to make mistakes, have things stall out, etc. It’s all part of the deal.

• Fermenting under pressure is a more stressful environment for yeast. More stress means you’ll need very healthy and viable yeast in solution to pull this off. 

• While pressurized fermentations do produce (particularly with lager yeasts) a far less pronounced bit of kräusen, you’ll want to avoid fouling the spunding valve. Watch your pressures and use a system that has a secondary pressure escape. 

• Because the beer will be naturally carbonated, you’ll need to take care to transfer the beer under pressure to preserve the carbonation.

• Dry hopping becomes trickier because beer geysers tend to happen when you introduce fine little bits of hop matter to a carbonated liquid. Many of the same folks who sell pressure fermentation systems also sell various pressurized dry hopping rigs (popular with the hazy IPA crowd to reduce oxygen introduction). You could transfer onto the hops under pressure to keep the mess down. Skipping those, if you’re fast you can probably pull it off, or be safe and degas the beer before introducing the hops.

• If you’re going for speed, you’ll want finings to speed up your beer’s polishing. Drew does this by racking into a keg with Biofine Clear and a shortened dip tube. (Floating dip tubes are another option for you dedicated gear heads!) 

All told, when done right, a standard lager beer of reasonable gravity (~1.050) can be produced in two weeks at “ale temperature” (around 65 °F/148 °C).

Which brings us to the other point: When and why should you do this? And when should you not?

For us, pressure fermentation is an interesting technique, but one with little application to our preferred brews. Denny makes West Coast IPAs and Belgian ales, neither of which need/favor pressure techniques. Drew makes milds, cream ales, and saisons, and only one of those (cream ales) possibly benefits from pressure fermentation. The other two will lead him to talking your ears off about the value of open fermentation. 

To us, capping to start naturally carbonating is a no brainer if you use pressurizable fermenters. It’s standard practice and wonderfully economical. 

Full pressure fermentation makes the most sense if you either have the desire to quickly turn around clean, yeast-neutral lagers or you want to produce them while fermenting at more achievable fermentation temperatures. There are additional benefits around LODO (low dissolved oxygen) practices and avoiding hop oxidation as well, but we’ve talked before about the mismatch on technique to goals for our general practices. 

The other reason to do it? Because you want to. You want to play around with the seemingly impossible trick of pulling off a lager without lagering. You want other shiny toys to play with. Or maybe you just want to make a beer in an indecently short amount of time. Nothing wrong with any of those, but for us, it’s a nice technique to have in the brewing tool chest, but not our usual way of fermenting. As with all things brewing, be mindful of why you’re doing the things you’re doing and what goals you hope to achieve!