High Gravity Brewing – Part 1 of 2

Following the success of DCHB’s annual High Gravity meeting, you may be inspired to try your hand at brewing a strong ale or lager.  You should definitely do this, and what follows is an outline of issues and tips for successful high gravity brewing.

1. Styles

For reference, the BJCP substyles in the 7%-and-up range include:

Doppelbock/Eisbock     Baltic Porter     Foreign Extra Stout

Russian Imperial Stout  Imperial IPA    Weizenbock

Dubbel                       Tripel              Golden Strong Ale

Dark Strong Ale           Old Ale            Barleywine

And of course there’s the Specialty category, which can include any other high gravity or “imperial” beer you might conjure up.

2. Recipe Design

First things first: Ensure your recipe contains enough fermentables for yeast to convert to alcohol.  This will mean using several more pounds of malt (or an extra can or two of malt extract) than you use in a typical average-strength beer recipe.

For example, if you typically use 10lbs of malt in an all-grain, average-strength 5gal batch, you might be looking at 15lbs or more for a high gravity batch of the same size.

The bulk of that malt should be composed of base malt(s), such as Pale or Pilsener malt.  Base malts contribute the greatest amount of enzymatic activity to convert starches into fermentable sugars during the mash.  In contrast, specialty malts and adjuncts, such as Brown malt or rice, contribute far less—or no—enzymatic activity, and require the enzymes from base malts to convert their starches.

Another method of increasing fermentables and gravity involves adding adjunct sugars during the boil.  Common adjunct sugars include honey, maple syrup, molasses, and candi sugar.  If overdone, they can impair fermentation and leave behind a phenolic character, so be sure to use in moderation.

Once your recipe is optimized for higher gravity, you’ll need to use enough yeast to actually convert those fermentables into alcohol.  A good rule of thumb for high gravity brewing is to use 2 vials or packs of yeast for a 5gal batch.  A better rule of thumb is to prepare a few days ahead of time and make a large yeast starter, roughly 3 or 4 liters.  An inadequate quantity of yeast will result in those cells being overworked and stressed, which in turn will result in flaws in your beer.  Not to mention, you risk not achieving your desired final gravity.

Before pitching yeast, but after chilling, aerate the wort extra thoroughly.  High gravity wort, by definition, is dense and yeast will require sufficient oxygen to reproduce and grow without being overwhelmed.  There are a few different ways to aerate wort, including vigorous stirring or submerging an oxygen stone.

When choosing a yeast strain, ensure the strain has adequate attenuation and alcohol tolerance.  Attenuation refers to the relative amount of fermentables the yeast will consume and its ability to reduce the gravity of the beer.  Alcohol tolerance refers to the yeast’s ability to continue fermenting in the presence of increasing levels of alcohol.  A strain, even if highly attenuative, could begin to die off if it cannot tolerate abv levels above, say, 7 or 8%.

Finally, although hops won’t affect gravity or alcohol content, consider using more hops than your typical average-strength recipe—ales especially.  Depending on style and desired characteristics, the added bitterness and hop flavor will help to balance the potential sweetness and intense malt flavors of a high gravity brew.

Continue reading Part 2 of High Gravity Brewing.