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The Rare Barrel
April 13, 2017 | The Rare Barrel

Balancing Act | Approaching Barrel Cellar Balance at The Rare Barrel

It is important to have a diversity of beer in our cellar to blend beers from. This diversity comes into play in different ways: when blending 3 - 4 oak barrels together for draft-only experiments a single barrel can have a significant impact on the final beer; yet, when we blend some of our larger releases we take a wider viewpoint to examine batch specific attributes (a “batch” is a single brew session, and typically results in about 14-15 oak barrels). Over the last year, cellar diversification has become a focal point amongst our production team. My intention with this blog post is to  give a glimpse of what variables we are currently taking into account when designing our sour blending beer, and where you can expect us to go in the future.

“Cellar Balance”

We talk a lot about “cellar balance” at The Rare Barrel, but what that means can be a bit elusive. On the most basic level, “cellar balance” means that we have groups of barrels with different characteristics, allowing us to blend for new as well as previously released brands. For example, if we are making a stone-fruit beer like Map of the Sun (our golden sour with apricots), we will blend toward a drier base beer that can reinforce or accentuate the apricot; but if we are making a beer like Home Sour Home (our golden sour with peaches, cinnamon and vanilla bean) we will seek out a beer that will have a pie-crust character. Both beers will use gold stock as their base, but because we have over 700 oak barrels of gold beer to choose from, we can play up certain attributes through barrel selection.
To conceptualize cellar balance, we tend to think of our barreled beers in loose, informal categories. Perhaps the most basic category is beer color. Since opening, The Rare Barrel has made four core “colors” of wort -- gold, red, dark, and black -- that are associated with four of our “core” brands -- Forces Unseen, Another World, Shadows of Their Eyes, and Ensorcelled. The majority of our beers use our gold base malt recipe, so 85% of what we brew is gold wort; we do, however,  brew our red, dark, and black base malt recipes throughout the year to have beer of different ages on hand for blending.
A few of the other prominent categories we consider when discussing cellar balance are acidity level, aromatics, age, dryness, and bitterness, all will be discussed further below.

Diversifying the Cellar

So, how do we create “cellar balance”? Let’s go through some of the variables that we use to diversify our barrel cellar.
Microbes: Perhaps no variable is more impactful on our beers than the microbes we use. Many of our early beers were fermented with a blend of Brettanomyces var. Drei and Lactobacillus Delbrueckii, but as we have continued to seek out new and different fermentation profiles we have vastly expanded our yeast and bacteria catalogue.  Currently we use yeast from many of the major brewing traditions (Belgian, French, American, British), and are continuing to explore the range of Brettanomyces available to commercial breweries. Oftentimes we will split our gold base wort into two fermenters, each with different yeast and bacteria. (Right now we have our gold recipe in one fermenter with a DuPont & Brett Blend and the other with Omega C2C Yeast.) If you’re interested in reading more on how we select and use yeast and bacteria at The Rare Barrel, check out our blog post (An Overview of Fermentation at The Rare Barrel).
Inoculation Timing: In addition to selecting different inoculants, another variable we tweak is the timing of when a beer might see either Brettanomyces and/or souring bacteria. Phenolic expressive (POF+) strains of Saccharomyces will leave compounds in the beer that some strains of Brettanomyces can later transform into some really delicious and unique flavors and aromas (one commonly discussed pathway is the transformation of the clovey 4-vinyl guaiacol found in hefeweizen to the funky or “horsey” 4-ethyl guaiacol). If the beer is inoculated with Brettanomyces alongside Saccharomyces, less of these compounds will be available for transformation, and the result is typically cleaner. Bacteria tends to grow at a faster rate than yeast, and can also diminish some of the flavors and aromatics created by yeast. Adding bacteria early in fermentation (when sugar is still available) will result in accelerated acid development at the expense of depth and complexity; adding it after both Saccharomyces and Brettanomyces have taken their turns results in less acidity, a generally longer timeline, but a more complex and nuanced beer. (Note too that most brewing bacteria are inhibited to varying degrees by hops, so that is another variable to attend to.)
Hops: We joke that hops were once a four letter word at The Rare Barrel, but through experimentation they’ve made their importance known and are now included in every batch we brew. Hops inhibit the growth of gram-positive bacteria (like Lactobacillus and Pediococcus), so they are a powerful tool in tempering acidity. We’ve found that even with a fairly robust hot-side hopping rate (~25 IBU), our house-adapted bacteria cultures will still produce acidity. Hops have aided our attempts to create more nuanced blends of sour beer, and we are excited to expand our exploration to include a wider range of varietals.
Malt Bill: Responding to patterns that we notice across numerous batches, at times we have tweaked our base recipes by swapping out or adjusting the percentages of particular grains. In recent batches of our black wort recipe, for example, we’ve subbed out American crystal malt for British crystal malt -- we’ve found that in our beers the British crystal results in a richer maltiness, while American crystal tends to be drier, grainy, and has a single-note sweetness. Right now we are in the process of updating our red recipe with the goal of drawing out more intense berry flavors.
Barrel History and Preparation: Oak is a porous material, and as all of our beers rest for 4 - 16 months in barrels, microbes penetrate and find a home in the wood of the barrel. When barreling down fresh beer, we consider what the previous tenant of that barrel might bring to the table. If we think that the resident microbes will be a good fit for the beer going in, we will either rack directly atop of the yeast and bacteria slurry, or we will lightly rinse the barrel with cold water and then rack in. If we wish to temper the impact of the previous beer on the new batch, we will use a high pressure gamma-jet to rinse the barrel with ozonated water, and then steam the barrel. Steaming will knock back the microbes for a while, but we’ve found that there is no way to entirely obliterate the impact of previous barrel residents.
Non-Sour Beer: Although we have been “All Sour Since 2012,” we do have beer in our cellar that is *gasp* not sour. Typically these are Saccharomyces / Brettanomyces beers that have gone into ozonated barrels. These beers have been a great tool as we look to draw back the acidity of some of our beers and to layer in a wider range of flavor and aromatics. These non-sour beers are created just as blending components and continue to impact the range of sour beer that we are able to blend--we have no intentions to release them on their own.
Although we talk of the goal of a having a “balanced” cellar, the effects of our efforts can take from 4 - 12 months to fully develop. Balancing really is a continual and reactive process.
Post up any questions and I’ll do my best to respond in a timely fashion.
Aaron Wittman
Research & Development Coordinator



Taylor's Gravatar
@ Apr 13, 2017 at 11:07 AM
Thanks, Aaron. Loving the continued posts providing insight into your processes- super helpful to me as a homebrewer, and grows my respect for TRB as I learn more about what you do.

While you make stellar blends, I love your effort put into finding unique barrels that are singularly expressive enough to not blend. Seeing Jay, Lauren, and Vinnie expose this process was inspiring to me. I'm wondering how frequently you come across a "rare barrel" like this without a deliberate search? What's the criteria for deciding whether to blend it or bottle it alone?

Also, on the hot side, I'm curious if you've experimented with varying mash temperatures and assessed differences in Brett/bacteria expression? There's some debate as to whether mashing high promotes more character as brett slowly chews through sugars left up for grabs by sacc. With the range of different recipes in play at TRB, I'm curious if you have any input on this?

You rock.

Julian's Gravatar
@ Apr 13, 2017 at 5:49 PM
Fantastic post. I have the feeling from reading a few posts that, for example the Sour Tooth Tiger, is the taste (ginger) blended in? I.e. would you place differing levels of ginger in certain barrels so that you can manage the end ginger profile by blending? If so, there would be barrels that you take snippets of, what do you do with that beer leftover? Is there often much?

Katya's Gravatar
@ Apr 14, 2017 at 5:58 AM
Does barrel aging a beer increase its abv at all? Is there any kind of osmosis or fermentation happening in the barrel happening during aging?

Aaron Wittman's Gravatar
Aaron Wittman
@ Apr 14, 2017 at 11:52 AM
Thanks for responding everyone --

@Taylor - While there are certainly some exceptions, there tends to be a fair amount of homogeneity across each batch we brew, provided it goes to barrels that have been "treated" similarly. If we are looking to explore variation across a certain batch we will mix up our barrel treatments -- some will be cold rinsed only (and therefore have more of microbial load in them), others will be hot rinsed, others steamed (our "scorched earth" approach), etc. Each of us in production have favorite barrels and batches, but it is rare indeed (forgive me!) to find a barrel or batch that we think is complete and balanced on its own. It is a fun exercise to cull through the cellar to find these barrels, and we're always on the lookout for sure, but most often we find that there's no substitute for blending. Barrel P9T (the 2016 "Rare Barrel") has been the only single-barrel beer we've released since I've worked here (~2.5 years), although I do believe Jay did some small batch stuff when TRB first opened so there may have been some single barrel releases back then.

We have and continue to vary mash temps across batches--generally depending on the maltbill that we are using, and what niche we see that beer filling in the cellar. While we haven't tied these experiments directly to brett / bacteria expression (there are so many variables there), I'm certain it has some impact. Far more impactful, however, is the timing of inoculation with brett / bacteria (during primary? after sacc? etc.) and the timing, breed, and amount of hops used on the hot side.

@ Julian - I think it'd be easiest just to step through how we make most of our "spice" beers: 1. Using small flask trials, we determine the amount of the ingredient we'd like to use. We then scale that up to our desired batch volume. 2. We will come up with a base blend of barrels we think ideal for the beer and homogenize the blend into a brite tank. We blend with entire barrels only. 3. We place the ingredient in our torpedo (basically a separate tank with ingredient screens), and purge the vessel with CO2. 4. Using CO2 pressure, we push the blended beer into the torpedo and steep the beer with the ingredient. 5. We push back to the blending tank, and repeat the process until we reach our desired level of extraction. 6. We compost the spent ingredient.

@Katya - Yes and no. Barrel aging by itself does not increase the ABV. Because we employ brettanomyces and bacteria in making our beers, during the barrel residency there is a slow secondary fermentation that occurs. This slow fermentation can increase the ABV up to ~.5%.

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