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High Gravity Brewing


By Victor E. Buckwold (Brewing Techniques)


Enjoying High gravity beers


Brewing beer with a high ABV can be intimidating. This article aims to offer up some easy-to-follow guidlines and procedures that can be utilized while brewing high gravity beer to reduce some of the intimidation. 



The principle behind high-gravity brewing is simple. You create a wort that has an original gravity significantly higher than the target and dilute it with water before packaging. Professional brewers are famous (or infamous) for the practice, and extract brewers dilute concentrated worts all the time. High-gravity brewing, however, has broader application to home brewing than most people realize. I believe that if you take care to compensate up-front for the effects of dilution, high-gravity brewing can help you to make more beer in a single batch with your existing equipment without loss of quality. Furthermore, dilution after fermentation can allow you to maximize your production capacity, without the need for more or larger fermentors.
Having said that, I’ve no doubt that many brewers are cringing at the thought of diluting their beer with water. I, too, like many of you, started making my own beer as an alternative to the typical watered-down beer mass-produced in North America. My goal has always been to make the best beer that I can, but if I can make more good beer in the same amount of time, and with the equipment that I have available, this is better still.
The almost complete absence of written material on the subject of high-gravity brewing and beer dilution in the home brewing literature is understandable in light of the way the discipline developed and matured. Most early home brewers began brewing to drink beer with more flavor, with a more distinctive color, with more hop character; by definition, not a watered-down beer. It’s not surprising, therefore, that people who appreciate good beer look down upon the whole concept of diluting beer. Professional brewers created the term “high-gravity brewing,” which implicitly refers to the production of a stronger beer that is subsequently diluted with water. Professional brewers may also refer to such beer dilutions as the “blending” of the product, though this term technically refers to the mixing of beers with other beers or with liquids other than water. We should of course note these courtesies when we speak to other brewers, but should bear in mind that what we are talking about today is, in reality, the dilution of beer with water.
Despite our prejudice against the practice, high-gravity brewing deserves consideration as a viable option within home brewing. The home brewing craft has evolved over the years, and we now need to face the reality of the situation — our beer production levels are limited, as are our resources and time. While it is possible in principle to brew several batches consecutively or to stagger the production process by, say, starting the first phase of brewing again when you reach the second phase, thus producing two batches the same day, the time involved and the energy you expend increases significantly. For me, double brew days are impractical. And again, no matter how you produce your beer — be it through the production of multiple batches or by staggering production — your output level is limited.
By adding some water to your beer, you can strike a happy medium between full beer flavor and otherwise limited production. Cost-effectiveness can be achieved by producing more beer in the same amount of time (additional ingredient costs will factor in, though ultimately water is cheaper than beer). Further, these techniques require little or no additional investment in equipment and little if any additional time spent brewing.
The other factor to consider is, what do the potential consumers of this beer want? In my household, opinions differ as to how strong a beer is acceptable. Home brewers are forced to consider both how to increase beer production and how to cater to the needs of the “consumer.” In reality, these considerations lead to the need for compromise, and if you’re just not willing then this article isn’t for you. But if these problems have come up in your brewing life, or if you are simply interested in increasing your production capacity without added effort, I urge you to keep reading. Home brewing is, after all, about creative solutions and experimentation. Cringe though you may, it may be time to consider high-gravity brewing and dilution in your home brewing practice.


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Factors to Consider when High-Gravity Brewing


The principle of high-gravity brewing and dilution is no secret to professional brewers, but for home brewers attempting this method a few key points need to be kept in mind before starting.

The dilution point: Extract brewers are familiar with dilution; virtually every extract brewer boils a concentrated wort and transfers that wort to a fermentor containing several liters of water to accelerate the cooling of the wort. More water is added later to make up the volume to the final batch size. In this article, however, I propose adding water to the finished beer, after fermentation. Only with this method of dilution can you push production capacity beyond the nominal capacity of your fermentor.

Style limitations: High-gravity brewing is only practical when you are producing average- to medium-strength beers. Strong beers such as barleywines and Dopplebocks depend on all the gravity the brewer can get from the malt, and diluting these beers would be counterproductive. You can also only put so much grain in your mash tun, so you would have to produce a smaller batch with primarily the first runnings from lautering. Furthermore, limits to alcohol tolerance in brewing yeasts mean that it is practically impossible to brew extremely high-gravity beers (say, >12% alcohol [v/v]) for dilution to target high-alcohol finished beers. I therefore propose that high-gravity brewing with dilution applies to the production of finished beers with target alcohol contents of up to 8% (v/v).

Dilution limitations: If you’ve ever been on a large commercial brewery tour, you may have tasted samples of their undiluted beer. You were probably pleasantly surprised at the flavor and character. Make no doubt about it — professional brewers can make good beer! They just seem to get carried away with their water additions. Beer can be diluted only so much before it begins to taste watered down.

The general rule of thumb in the brewing industry is that beer can be diluted up to 30–40%. If we consider this range the practical limit (and an extreme that most of us would wish to avoid), it is easy to imagine that adding less water will have very little effect on the final product. With the proper recipe adjustments, the addition of 10% water to your beer will make very little difference to most people’s perception of the beer, yet it can affect your level of production significantly. If you were to use a fairly conservative 20% dilution, you could increase a 5-gallon batch to 6 gallons. That means that you can produce as much beer in five batches as in your last six.


Good Water Makes Good Beer

The water used for diluting your beer must be sterile and free from other unwanted elements, including chlorine, oxygen, and possibly minerals. You can prepare your own water at home by boiling and cooling it in advance. Any oxygen in the water will oxidize compounds in the finished beer, shortening shelf life and leading to off-flavors. Boiling effectively deaerates the water. If you boil your water, try to keep it cool afterwards so that it takes up less air (oxygen) from its surroundings. Avoid adding air to the water (and beer) by racking it carefully into the beer. This issue is less of a concern in the case of bottle-conditioned or kegged beer than in beer in which the yeast has been removed because the yeast act as natural oxygen scavengers. Nonetheless, the presence of air in beer should be avoided almost as scrupulously as the introduction of microbial contaminants.

In principle, carbonated water is the best type of water to use for diluting beer because it is oxygen-free and will not dilute your beer’s carbonation. Be sure to read the label carefully; some contain sweeteners, salts, or other undesirable ingredients. If the beer is fermented again in the bottle or in a keg to achieve carbonation, carbonated water is not necessary.

Bottled distilled water is always a good source and is what I use. Most bottled brands of drinking water have little if any microbial contaminants in them and should be suitable for dilution. I always avoid mineral waters because of their mineral content and also because some brands are aerated. Pure drinking water that comes from a machine should not be used because in addition to the mineral content the quality control is much more variable (you can’t trust the water around the time a new filter is due).


Other considerations: High-gravity brewing requires higher quantities of every ingredient to match the characteristics of a beer brewed normally — more malt, more hops, and more yeast. High-gravity brewing also creates new issues for the brewer. Studies have shown that high-gravity beers, whether diluted or not, have poor head retention compared with beers of normal gravity. It has also been observed that high-gravity environments decrease hop utilization and cause some yeast strains to underperform. Adjustments may also need to be made for color. Fortunately, brewers can address these problems through recipe adjustments, as discussed below. The water you use for the dilution is also very important, especially since it’s being added after fermentation.


Recipe Adjustments


High-gravity brewing offers two possible approaches. First, you can simply take an existing recipe and dilute it after fermentation to produce more beer of roughly the same character. As previously noted, dilutions of 10–20% may be barely perceptible to some consumers. On the other hand, if you really want to hit specific recipe or style targets with your final (diluted) beer, you can reformulate the recipe to compensate for the effects the dilution will produce. This section describes recipe adjustments you may wish to make to achieve the results you want after dilution.

Basic linear scaling: Most components of the beer will dilute down in a linear fashion. If you have 7% alcohol (v/v) in 5 gallons of beer after fermentation, for example, diluting to 5.5 gal-Ions (a 10% dilution) will yield a beer with 6.4% alcohol, and diluting to 6 gallons (a 20% dilution) will yield a beer with 5.8% alcohol. Likewise color, bitterness, and other factors will dilute more or less linearly (see the section “Make color adjustments” for dilution effects on dark beers).

The following equation can be used to predict the change in concentrations of these constituents in the final, diluted beer:

ConcentrationF = (VolumeO ÷ VolumeF) x ConcentrationO

where ConcentrationF is the component’s final concentration (after dilution), ConcentrationO is its concentration before dilution, and VolumeO and VolumeF are the batch volumes before and after dilution, respectively. Thus, if you brew and ferment a 5-gallon batch that registers 6.3% alcohol and dilute it 20% to 6 gallons, the alcohol content after dilution will be 5/6 x 6.3 or 5.25%.

This equation can be turned around to help you adjust a recipe to produce a final diluted beer that still conforms to specific style targets.

(VolumeF ÷ VolumeO) x ConcentrationF = ConcentrationO

Using this version of the equation, you can specify a final, after-dilution alcohol content of 6.0% and determine that you need 6/5 x 6.0 or 7.2%, in your predilution beer to achieve the desired result after dilution.

Bolster specific gravity with fermentables: To increase the gravity of your beer, you will need more fermentables in the form of grain, malt extract, or sugar to make a higher gravity beer. It’ll cost a bit more up front, but remember that you’ll be saving down the road.


Dilution Directions

I find it best to choose the extent of dilution of the beer in advance so that I know how much more hops, specialty malts, and fermentables to add to make a beer that will be flavorful even after dilution. It also helps me plan the volume of water that I need and how I will undertake the dilutions. You can, if you like, take a small sample from the fermentor and try various dilutions in a glass before deciding on the dilution to use. But I suggest that you simply start out conservatively with, say, 0.5 gal of water for a 5-gallon batch (10% dilution), and increase the dilution with successive brews according to your own tastes. Good brewing notes are essential to the optimization of any step in the brewing process, and good notes will serve you well in your experiments with high-gravity brewing and dilution.

The only things that you need to successfully package the diluted product are a larger container that can accommodate the volumes required and high-quality, sterile, deaerated water. A new large container is not absolutely essential but will make things easier. If the total volume you plan to package is greater than that of the container you now use for racking, you will have to divide the process into two steps and rack, dilute, and package the first volume, and then rack, dilute, and package the remaining beer. Also, you may need to calculate the amount of water to add to each volume separately if the volumes are different from each other.

A known volume of water should first be added to the racking container by gently racking it in to avoid splashing. If you plan to bottle-condition, next add boiled priming sugar at the standard rate of ¾ cup per 5-gallon batch (or the appropriate proportional amount for the volume you are bottling). Next add your beer, again carefully, by placing the spout of the racking cane below the surface of the water to fill the container from the bottom up. Mark the side of the bucket in advance with ticks corresponding to gallon volumes to help you calculate your dilution. For instance, if you fill the bucket with 1 gallon of water, and then add your beer until it reaches the 5.8-gallon mark, you have diluted your beer by 1 gal water/(5.8 gal – 1 gal water) = 0.21, or 21%.

Wait 5–10 minutes to allow the solutions to mix completely before bottling. If everything goes into one keg you needn’t wait. This process can be accelerated by stirring with the bottling cane. Always blend beer by adding the lightest liquid to the bucket first. If the denser liquid is added first the mixing may be somewhat less efficient unless the liquid is stirred.

For the pros: Microbrewers generally do not perform dilutions, both because of the “taboo” of diluting beers and also because special equipment is required to manage the large volumes of water and beer used. Large volumes of clean, oxidant- and chlorine-free water need to be boiled (or deaerated with dedicated equipment), cooled immediately so as not to take up oxygen again, and carbonated. The dilution needs to be performed using a special partitioning device to measure the volumes added and to affect the mixing process. In short, a micropub would never try this, and if a microbrewery would they wouldn't tell you about it. 


Few all-grain brewers really push the envelope of their systems, and most therefore have the capacity to produce higher gravity worts with ease. Should you reach the upper limit of your mash/lauter production capacity, however, then your only recourse to produce even higher specific gravities is to add kettle adjuncts such as honey, glucose (for example, corn sugar), or malt extract during the wort boil. Bear in mind the influence each source of fermentables will have on the final product. Refined sugars should be used conservatively (<10% of fermentables) because they will tend to thin the body and may contribute cidery (sucrose) flavors and other undesirable properties to the finished beer. Honey, if used in high quantities, may contribute honey flavors. Malt extract is often notoriously low in yeast nutrients; sugar and honey are also nearly devoid of yeast nutrients. Low yeast nutrient content can lead to fermentation difficulties. Yeast energizers, yeast nutrients, or yeast extracts may be advantageous in promoting yeast growth and boosting fermentation when kettle adjuncts contribute more than about 25% of the final wort gravity.

Note that if you’re brewing with extract alone, you are already boiling a concentrated wort and it is not advisable to further concentrate the wort by much. The simple sugars in malt extract are very soluble in water, so it is theoretically possible to create extremely high-gravity worts with malt extract. Glucose, for example, is soluble in water to concentrations as high as 1 g/1.1 mL (0.91 g/mL, or 91 °P)! This potential for concentration should come as no surprise to extract brewers; extract syrup is diluted manyfold for the boiling of the wort and again subsequently for fermentation.

Brewing with molasses-like gravities directly is not realistic for a variety of reasons. As mentioned earlier, very high levels of sugars actually inhibit yeast growth, and the most alcohol-tolerant (ale) yeast can typically ferment only to about 12% alcohol (v/v) (which is why tables of specific gravity for brewers stop at about S.G. = 1.100 [24 °P]). Lager yeast tends to reach its limit at much lower gravities. Also, highly concentrated wort can lead to increased caramelization because of the concentration of sugars at the point of contact with the heat source.

To determine how much more you will need in additional fermentables, start by applying the linear dilution equation to your recipe’s gravity specifications. If, for example, your base recipe has a starting gravity of 1.056 and a terminal gravity of 1.012, your usual beer will have a drop in gravity of 44 points (5.7% alcohol [v/v]). If you plan a 20% dilution, increasing your final volume from 5 gallons to 6, you will need to increase your gravity spread to 6/5 x 44 or 53 points to keep the resulting beer as similar as possible to the original, for a new target original gravity of 1.065.

Note that this method is a rough approximation only. If you begin with an original gravity of 1.065 instead of 1.056, your final gravity may be 1.013 or 1.014 instead of 1.012, depending on the yeast strain used, the overall wort composition, or other factors. Attenuation (percent drop in gravity during fermentation) is reduced in higher gravity worts, and more fermentables will be required than will be predicted by the linear scaling equation. Nevertheless, this simple equation does provide a starting point for recipe adjustment.

Preserve mouthfeel and body with specialty malts: Try this experiment: Open up a new bottle of beer (preferably a homebrewed or microbrewed variety; 16 oz = 2 cups) and divide it between two glasses (1 cup = 8 oz = 16 tbs). To one glass add 1.5 tablespoons of water (a dilution of approximately 10%), stir, and compare the two. What do you taste? Not much difference! But if you keep slowly adding more water, the first thing you should notice is that the beer gets thin in body. Such over-dilution is often one of the complaints that home and micro-brewers have with typical commercially available beer.

All-grain brewers can easily address this challenge by adding a small proportion of carapils or another highly dextrinous caramel- or crystal-type specialty grain to the mash. The extra mouthfeel and body that the unfermentable complex carbohydrates and starches in these malts contribute to the beer will help to maintain the full beer sensation in the final diluted product. Professional brewers know this, too, but perhaps have less sense of when they have diluted their beers too much. Don’t get carried away with specialty grains — 5–10% is usually sufficient (unless you’re brewing a stout, of course). Even 3% in the mash should make a notable difference in mouthfeel sensation in the final product. Extract brewers can either partial mash using 50% cara pils and 50% regular malted barley or steep the specialty grains directly in the kettle.

Adding cara pils or crystal malt to the grist helps to improve head retention as well (remember, high gravity-brewed beers often exhibit head retention problems). Small quantities (say 1–5%) of wheat malt or oats may also help. But remember, keep the overall total specialty grain bill under 10% for most beers because these grains can easily overpower a beer’s flavor and color profile.

Make color adjustments: When you dilute any beer you also dilute its color. If you want your beer to have some significant color component, you will need to adjust the proportion of specialty grains in the mash to compensate for the dilution’s effect on color. The easiest way to figure the color dilution factor is to use malt color units (MCUs), which rely on malt color as the primary predictor of beer color. One color unit is equal to 1 lb of 1 °L malt. To calculate MCUs for a given type of malt, just multiply the amount of malt (in pounds) by the malt’s color rating (if not provided with the malt when purchased, malt color charts are available in most homebrew literature, including reference 3).

If we brew 5 gallons, for example, using 7 lb of a base malt with a color rating of 2 °L (14 MCUs) and various specialty malts with a combined MCU value of 36, the 5-gallon batch will contain 50 MCUs, or 10 MCUs/gallon. If we dilute the batch by 20% (increasing batch size to 6 gallons), then 50 MCUs will dilute to 8.3 MCUs/gallon. This would mean that the beer is still in the amber range, but could use a boost from some roasted grain to keep the darker color intact. To adjust the grain bill to make the final diluted product consistent with the originally intended color, use the linear scaling equation. For the (diluted) 6 gallons to have 10 MCU/gallon means you need 60 MCUs in the recipe 6/5 x 50 = 60.

A caveat on color: MCUs are a rough-cut estimation tool, and because malt color alone is not the only predictor of beer color, MCUs cannot necessarily be compared with actual, measured Lovibond/SRM values. Whichever color measurement system you use, stick to it throughout your recipe formulation work to achieve consistent results. With dark beers, the dilution of color is not linear, and diluted dark beers tend to be darker than the linear scaling equation would predict.

Hop adjustments: Hop contributions also dilute linearly after fermentation, and therefore the linear scaling equation can be used to predict dilution and to adjust hop charges accordingly. Bittering hops, however, provide a special circumstance that warrants attention.

Bittering hops need two adjustments. Hop utilization decreases as wort gravity increases, so in a high-gravity boil you need to add more hops than usual even to get the same level of bittering from the hops. If you are planning to dilute the finished beer, however, you will need to add even more hops to get the additional bittering units needed to then dilute down to the target level of bitterness.

First, begin by determining the number of bittering units you expect from your recipe or need in the final beer; say, for example, 30 IBUs. We know from the linear scaling equation that to have 30 IBUs in the beer after diluting a 5-gallon batch 20% to 6 gallons we need 36 IBUs in the initial 5 gallons. The question then becomes, “How do I get 36 IBUs in my kettle?”

The question of hop utilization and estimating hop bitterness has generated considerable difference of opinion and different calculation models within the specialty brewing community. Hop bitterness is determined by a number of variables and can really only be measured in a lab; calculations can thus provide only guidelines. This article cannot presume to cover this topic in depth, but for the sake of demonstration consider one example based on Glenn Tinseth’s well-known model. According to Tinseth’s model, if you boil a 1.065 wort for one hour using whole leaf hops, you will achieve a 20.2% utilization factor. Using Tinseth’s IBU calculation, you can determine the amount of 6% alpha-acid hops required to achieve the 36 IBUs needed for the 5-gallon brew:


IBUs = Utilization x (Decimal AA Rating x ounces of hops x 7490)/Volume

36 = 0.202 x (0.06 x ounces of hops x 7490)/5

Ounces of hops = 2oz.


Thus, 2 oz of 6% alpha hops boiled in a 1.065 wort will produce 36 IBUs, which after fermentation can be diluted 20% to contribute 30 IBUs to the finished, diluted beer. Note that you could use a smaller amount of higher-alpha hops to achieve the same effect.

Hop flavor and aroma additions follow the linear scaling model, assuming the flavor additions are added late in the boil and are not counted on to contribute alpha-acids for bitterness.

Support your yeast: Some basic yeast biology is relevant to any discussion of high-gravity brewing because in some cases the yeast strain may limit the production of alcohol. Some strains of yeast can ferment only lower gravity brews completely. A high-gravity brew fermented with such a yeast might end up too malty or sweet.

Obtain alcohol-tolerant yeast. Almost all of the high-quality liquid yeast strains commercially available today can produce beers of 10% alcohol (v/v) or higher, but if you run into troubles, the yeast strains labeled “alcohol tolerant” are the best choice. Highly flocculent strains are undesirable because attenuation is related to the ability of the yeast to remain in solution for a sufficient period of time.

Some brewing texts suggest that Champagne yeast may be beneficial for brewing beers of high alcohol content because they can ferment worts of higher gravity than brewers yeast, but I do not recommend their use even for ultra high-gravity brewing. Champagne yeast produce different (Champagne-like) results, and today’s alcohol-tolerant brewing yeasts should be sufficiently hardy to make beer-like products. In addition, Champagne yeast aren’t very flocculent, and because they almost never come out of solution they can be very difficult to remove to achieve a clear beer.

Aerate fully. Another point to keep in mind is that higher gravity fermentations require more yeast, and increased aeration of the cooled wort before pitching encourages yeast growth. If you have trouble reaching your target terminal gravity, try rousing the yeast. If your fermentation becomes “stuck,” adding fresh yeast may also help.

Pitch generously. It is also of paramount importance to propagate sufficient quantities of yeast before pitching. Inadequate quantities of yeast will lead to sluggish fermentations and the production of higher-alcohol derivatives, which some believe contribute to hangovers.

Two pouches of dry or liquid yeast cultures are hardly better than one and will not be sufficient for good fermentations. At least 500 mL (~½ quart), and preferably 1 L (~1 quart) of healthy starter culture should be used, if possible, for a 5-gallon fermentation.

Acclimatize your yeast. If you reuse your yeast it is worthwhile to note that yeast will become “acclimatized” to the conditions under which they are grown. Yeast that have been grown in high-gravity wort for many generations will perform better in this environment. Conversely, a yeast that is accustomed to low-gravity worts will need time to adjust to newly imposed high-gravity surroundings.


Push the Limits of Production


Following the suggestions outlined in this article, you can try a dilution experiment of your own and see for yourself if the benefits are real. I think you’ll find that a small dilution of the beer will go virtually unnoticed by many beer drinkers and will increase your production levels substantially without requiring new equipment. Try different dilution levels with different styles.

I like to bottle part of the batch for myself, possibly after a small dilution, and further dilute and bottle the remainder for imbibing by beer drinkers of mere mortal palates. I typically dilute my homebrew 20–25%; not one home brewer or micro-brewer out of the dozens who have tasted my beers would have guessed that the product was diluted if I hadn’t told them. Also, if you have friends who are not “hop heads” or diehard beer people, I guarantee you that they will appreciate a beer similar to that which they recognize as beer, instead of the 9% alcohol, 50 IBU, black-colored stout you love so much. Who knows, you might like it too!

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