Since pitching my sour culture into a lambic for the first time and yielding good, albeit early, results I have begun to think about my long terms plans for making sour beer. I also started to consider how I might keep my culture going without allowing it to succumb to selective pressures that might reduce the diversity I expect that I have in there. A few recommendations I had about keeping the sour culture going included using a solera. This is something I have been thinking about for a while, so maybe now is the time.
If you’re unfamiliar with the solera process, you can check out the Wikipedia article. The general idea is that you have one or more barrels and remove some of the aged, generally sour, beer (or sherry or vinegar more traditionally) and fill back with newer or fresh beer. You can do this with one barrel, removing as much of the beer as you need and replenishing it, or you can do multiple vessels where the average age of the beer in each barrel is older than the previous. The beer is then taken from the oldest vessel and bottled for consumption.
My initial thoughts on starting a solera was to do it in the traditional sense and use a stack of three small barrels, in the 8-10 gal range. I would build this up over time, removing up to half of each barrel to fill the next (or blend some of the younger into the older to balance the end product sour beer if necessary). The youngest barrel would get an infusion of fresh wort. The trouble with this approach is that barrels are really expensive, so much so that a used 8 gallon barrel can cost as much, if not more, than a used 53 gallon barrel! Such is the way of supply and demand I guess.
My Plan for a Sour Solera
In order to get the solera going, my current plan is to start using PET carboys and then maybe transfer into barrels at some point in the future. PET carboys have the added benefit of not losing anything to evaporation through the wood like a barrel does, though some say correctly that it adds to the character, but no evaporation will make learning the process and managing transfers much easier. Some people have concerns about oxygen permeability with PET carboys, but I can’t imagine that there is anywhere near the oxygen transfer in a PET carboy as there is in a barrel, even if you wax a portion of the outside of a smaller barrel. I actually like a little acetic character to my aged sours, so if some O2 gets in and the assumed Brett turns out a little acetic acid I’ll probably be happy about it.
I am planning to use my Belgian Dubbel as the recipe for this project, which should result in a reasonable approximation of an Oud Bruin. It is a recipe I have worked on for a few years now. I used to make my own candi syrup, but once the commercial product became available my home made stuff couldn’t come close to matching it. Making the switch really upped the quality of the beer, and I would strongly recommend everyone to try it.
To get the ball rolling, I’ll brew up a 10 gallon batch of the Dubbel and keep half for the solera and ferment the other half with WLP500 or WLP530 (I go back and forth between those two). In order to get the solera going faster, I’ll plan to repeat the brew in 6 months, and then again another 6 months later. After 1.5 years I’ll have three carboys with beer aged 6 months, 12 months, and 18 months. Then I’ll expand the timeline to yearly brewing and space out the age between the carboys. I envision transferring about half out of each carboy, and refilling from the next youngest or adding fresh wort. A yield of 2.5-3 gallons each year sounds like enough to start with as I’ll likely bottle with corks and cages and naturally carbonate. I might even find my way to aging some of the solera beer on freshly harvested Michigan cherries (from my garden once i plant the trees!).
As this project will probably not get started for a few more weeks, and even then the solera part of it won’t be really going for another few months, I welcome feedback on the plan! I will, of course, update with posts throughout the process.
Update: a reddit comment reminded me that I forgot to include my intention to use oak spirals in the carboys as well. I’m unsure at this point if I will use them in only the oldest carboy or in all three. If anyone has an opinion of which way to go, please let me know.