When it comes time to blend their gueuze, traditional lambic producers have a brewery full of barrels to select from. They can sample from their barrels, select those to contribute to their gueuze, dedicate others to fruit beers, and tag others for continued aging (or the drain). You, in contrast, will have three buckets (if you follow the plan in the accompanying article). Still, if your three beers turned out well, you can still blend of very fine gueuze at home.
Characteristics Of The Beers
Sour beer fermentations can be somewhat unpredictable. Some variability in the characteristics of the final product is to be expected. Still, some generalizations will hold most of the time. The one-year-old lambic will (most likely) be somewhat sour, but still have some carbohydrates not yet fermented by the microorganisms. As such, it will (likely) show a small amount of body and sweetness. It will (likely) be the least sour of the three, and show the least amount of “funky” lambic aromas — barnyard, horse blanket, hay-like, etc.
In contrast, in the three-year-old lambic, the microorganisms will (likely) have completely utilized all the carbohydrates they can handle, or very nearly so. It will be the most dry and acidic. It will also (likely) show the greatest amount of lambic “funk.” The two-year-old lambic will (likely) have a character intermediate between these two.
As I mentioned, there is some variability in the process. You need to taste your beers to confirm how they turned out. I have found that, under relatively controlled conditions — temperatures within a reasonable window, fermenters remaining air-tight, etc. — variability decreases with time, at least in some respects. Sour beers get more sour and dry over time, and they begin to converge in the degree of tartness and dryness. The level and character of “funk,” however, may diverge.
On the other hand, if there is some problem — for example, if they are exposed to air — they can go “off the rails” and a veer off into a terrible, undrinkable mess. Whatever consistency I have experienced may be due, in part, to the fact that I have used cultured microorganisms — not relying on spontaneous fermentation or adding the dregs of other sour beers — for my fermentations. When you first sample your sour beers, be ready for whatever the sour beer gods have handed you.
The Simple Blend
If you start with three fermenters, at 5.0 gallons (19 L) of sour ale apiece, the simplest blend is to mix the full volume of all three sour beers together. This maximizes your volume, and gives you 15 gallons (57 L) of gueuze. If all three of your sour beers turned out well, the blend will likely also turn out well. Using this blending strategy also obviates the need to come up with a plan for your leftover sour beer.
The best tasting gueuze may not utilize all of your available lambic. Your beers will likely show varying degrees of sourness, “funk,” and residual sweetness, and you may want to tailor your blend to emphasize or deemphasize any of these characters. If you enjoy a very dry and acidic lambic, your blend should be dominated by the third year old lambic. For example, you may want to blend all 5.0 gallons (19 L) of the three year old lambic with 2.5 gallons (9.5 L) of the two year old lambic, and only a little over a gallon (4+ L) of the young lambic. This would yield between 8.5 and 9.0 gallons (32 and 34 L) of gueuze. The leftover lambic could be used for fruit lambics or racked to a carboy and stored for future use in other blends. (If you do this, make sure there is as little headspace in the carboy as possible. Add some CO2, from your CO2 cylinder, as further protection.)
For a mellower lambic, you may want to blend all of the two-year-old lambic with smaller amounts of the young lambic and enough three-year-old lambic to hit your preferred level of acidity and “funk.” You can take samples and make test mixes to determine your favorite blend. Remember that the beer will continue to age in the bottle, and will be highly carbonated once it is conditioned. When finished, the beer will be drier and more acidic than it is at the time of blending.
Blends with higher percentages of young lambic will be the least acidic and contain the most microorganisms. It is plausible to speculate that these gueuzes will condition faster than those dominated by old lambics. However, a gueuze blend should never be dominated by the young lambic. It will not be sour enough and could result in severely overcarbonated bottles.
Postponing the Blend
One option, albeit not a very enticing one, is to postpone the blend if one or more of the beers do not seem conditioned enough. If you do this, protect the beer by adding some CO2 to the headspace before you reseal the bucket.
Once blended and bottled, the gueuze should sit for at least a few months in a warm place (optimally mid-70s °F/~24 °C). Better yet, let it age about a year before it is consumed.
Gueuze is traditionally bottle conditioned, with enough added sugar to highly carbonate the beer (to 4 or 5 volumes of CO2). It is almost as highly carbonated as Champagne (which is often around 6 volumes of CO2). Given that your blend will include some young lambic, carbonation can be tricky. You can estimate the amount of unfermented carbohydrates left in the beer, based on your final gravity, but you do not know what percentage of them will be utilized by the wild yeast and bacteria during conditioning. A realistic approach is to aim for a target level of carbonation around 3 to 3.5 volumes of CO2, but realize that it may end up more highly carbonated than this.