Starting a Sour Solera

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Solera fermentations have been growing in popularity ever since Will Meyers implemented his system at Cambridge Brewing Company to age Cerise Cassee, an Amber colored sour wild ale with cherries. Solera is a technique originating in the production of Sherry but is also used in the aging of vinegar, brandy, wine and many other liquids for where there is a desire to blend old and new vintages. The solera system can be applied to any type of beer which would do well with aging and blending, but has become most popular in the sour/wild brewing community.
Traditionally a "Solera", which literally translates to "on the ground" in Spanish, is comprised of a series of oak barrels all filled at different intervals with product on a yearly cycle. At the end of each cycle a portion is pulled from the oldest barrel (called the Solera) and packaged. Then, each of the younger barrels (called the criadera, or "nursery"), are transferred down the line to refill the Solera. No barrel is ever fully drained, as the youngest barrels are topped off with fresh liquid to age and wait for next years cycle. The result is an evolving product of an average age year after year. On a more manageable homebrew level the same system can be maintained in a standard 5 gallon size using carboys, kegs, etc contained in one vessel.

Photo by Brian at brouwerij-chugach.com
There are a few variables to decide on when planning your own Solera, starting with choosing the base beer style. I use a pale Lambic-esque wort in my own cellar, but you could brew a Flanders Red/Brown, a Stout, really any type of beer you want. The goal here is to create a wort that is low in IBU's, to not inhibit the Lactobacillus, while leaving enough long chain unfermentable sugars for the yeast and bacteria to acidify over time. Keep in mind that when brewing a sour/wild ale, you want to make sure the flavors of the base beer compliment the flavors coming from the blend of yeast and bacteria. Try to keep it simple, stay away from using spices, or over hopping, you can play with those things when you package the beer.
With your base beer planned out, you will need to decide what type of vessel to age the Solera in. Some vessels to consider are glass carboys, Better Bottles, kegs (corny or Sanke), oak barrels, whatever size you're most comfortable maintaining. Oxygen permeability of the vessel is always a concern when aging beer this long, but especially with Brettanomyces and bacteria in the mix. When exposed to high levels of oxygen Brett can create acetic acid (vinegar flavor) so you'll want to keep oxygen exposure minimal. Furthermore, acetobacter, which has the ability to convert ethanol to acetic acid when exposed to oxygen, is a spoiling organism that can wreak havoc on your Solera. Although it can be appropriate in some styles at lower levels, you want to avoid as much acetic acid as possible in a Lambic type wort.
Stay away from using a plastic bucket or even a 5 gallon oak barrel (whose staves are much thinner than 50+ gallon oak wine/spirit barrels) both are more oxygen permeable than glass carboys, Better Bottles, and larger oak barrels (o2 Permeability chart from Wild Brews). I use a 15.5 gallon sanke keg to age my Solera as it is only oxygen permeable through the orange carboy cap on top and can store a fairly large volume.
With regard to microbes, they are as important as the vessel you are aging in, and probably more important than your base recipe. The players at work here are Saccharomyces (brewers yeast), Brettanomyces (a type of yeast known for its "wild" character), Lactobacillus and Pediococcus (both of which produce lactic acid). Saccharomyces will do the bulk of the fermenting in the early stages while Brett/Lacto/Pedio will acidify and add a wild "funky" character to the beer. Note, Brett alone will not make a beer sour, that's what the Lacto and Pedio do. For further reading on these organisms, see American Sour Beers by Michael Tonsmeire.
In my opinion, the best option is to buy a blend of these yeasts from a major yeast lab. I suggest WLP655 Belgian Sour Mix, Wyeast 3763 Roselare, ECY01 Bugfarm or The Yeast Bay Melange, to name a few. I am a firm believer in biodiversity for complexity, so as you age the beer add the dregs of some of your favorite sour beers right into your Solera, If you're interested in what dregs to use, Tonsmeire maintains an extensive list of viable sour dregs in commercial beers. I also like to add some medium toast oak cubes to my Solera, however make sure they've been boiled long enough so there is little to no oak flavor left. The wood can be a nice home for Brett and bacteria to live. In addition, Brett can also metabolize cellobiose in wood and create some unique flavors.

The hardest part after having brewed the first batch for the solera is the waiting. Resist the urge to open the vessel unless you're adding dregs or removing a sample. Remember oxygen could turn your project into vinegar. Carefully remove samples periodically take good notes on the tasting, take a gravity reading, and take a PH reading if you have a meter. If the gravity is stable after 1 year (it should be), you can pull a portion out to be packaged. I generally bottle or keg the first cycle straight so that you can get to know the base beer that is in your Solera. Usually I will remove one third to one half of the old beer leaving the rest in the Solera to be topped off with fresh beer or wort. Tonsmeire created a handy spreadsheet to calculate the average age of your Solera based on the amount removed and then topped off.
After tasting your first pull, give some thought as to whether you would want to modify the top off batch to adjust the beer for next years cycle. Ask yourself: Is it too sour? not sour enough? too funky? Prior to a recent cycle I felt my Solera was overly sour and needed some Brett complexity so I modified the top off batch to adjust. I mashed the beer at 160F and pitched WLP530 along with The Yeast Bay Brussels Blend, known for some classic Brett funky aromas, and increased the bittering addition slightly. Once the krausen started to fall I racked the fermenting beer into the Solera. Some people will drastically change their top off wort every cycle, and some people will keep it virtually the same each year. On a recent episode of Basic Brewing radio a National Homebrewers Conference attendee mentioned they increased the color on every top off batch from pale all the way to black, what a unique idea!

After the first cycle is complete you will have a good grasp on your Solera and will easily be able to determine when your next cycle should be. Whether you pull some to age on fruit, blend some into some fresh beer, bottle it straight, you can end up with many interesting vintages as your Solera progresses. One thing to keep in mind is that your Solera may have an expiration date - if it becomes overly vinegary (acetic acid) or has aromas of nail polish remover (ethyl acetate), you may want to consider ending your Solera and starting over from the beginning. Take good notes, plan ahead, be patient, and let the beer point you in the right direction. Remember don't remove that bung too often and keep those airlocks full. Funk it up!
Thanks go out to Ed for teaching us all about Soleras. If you would like to read more from the latest writer to join the HomeBrewTalk team please be sure to visit him at his blog, Ales of the Riverwards, and for more on his solera project please follow this link.

Awesome write up, Ed!! What about the yeast cake? Is it ok to leave the solera on the cake and top off with fresh wort, or should you let it ferment and age it in secondary?
@TheZymurgist Great question. Opinions vary on this topic but I age it on the yeast cake in the primary fermenter as is done traditionally in Lambic brewing. Brettanomyces has the ability to metabolize autolysing Sacchromyces cells so the fear of autolysis is minimal. Another reason I leave it all in one vessel from the start is to minimize oxidation during a transfer to secondary. If I didnt stress it enough, I am deathly afraid of Acetic Acid in my Solera.
But if leaving it on the yeast cake concerns you then by all means ferment the first batch out then rack into your aging vessel.
@Coff That's what I was thinking, but I've had trouble finding a clear answer. Thanks!! I plan on doing a three vessel solera, where one-third of each vessel is emptied and blended together, then the oldest vessel is filled with the next youngest, on down the line. Unfortunately this will be the ultimate test in patience, since it'll be three years before the first pull, but I think it will be a lot of fun!
Thanks for this article. I've been thinking more and more about doing this.
For me, it would probably be a 20g barrel with a 5g top up each year. Not quite solera, but I can only squeeze out enough space for 1 barrel.
Awesome information! Would your process change at all if you were to do this with something other than a sour, like an RIS? Would you let the Stout ferment out before transferring to the larger vessel for blending, or would the re-fermentation in the large vessel be beneficial?
@mrdauber64 I think the main concerns with aging a 'clean' beer like this would be not aging on the yeast cake, oxidation, and contamination. With Sacch, you definitely don't want it to sit too long on the yeast, so you'd want to ferment in primary, and transfer to secondary (preferably glass or SS.) Oxygen permeable containers like plastic and oak will pose an issue over the long term, as well as opening the vessel to pull samples. You also run the risk of it being contaminated down the road with wild yeast and bacteria. It's not as much of an issue if the beer is already contaminated with these organisms.
I thought about doing the same thing with a RIS or Barleywine, but I'd be worried about the long-term viability of it. Although I haven't completely ruled it out yet...
Great article! I want to find a 15G barrel, maybe 2, to do exactly this. Having a batch of wonderful wild beer every year is something I definitely aspire to.
@mrdauber64 The @TheZymurgist nailed it, great advice in his post. I think a RIS or Barleywine would be great for a Solera, but you deffinitely do not want to age the beer on the primary yeast cake.
@TheZymurgist and @coff. Thanks for the information. I think I am going to try this for an RIS using a 15 gallon SS keg. Brew three consecutive 5 gallon RIS batches, let them ferment out and then transfer them to the keg to blend and age. Then every year pull 5 gallons out and put 5 gallons of new completely fermented out RIS back in. I like the idea of being able to adjust the blend every year based on how it is aging and being able to pull 5 gallons of RIS out whenever you want(as long as you replace it) would be awesome.
Great article! I've been wanting to start a solera-esque setup for a little while now and I'm glad to have found this write up. My main concern with the continuous nature of the solera is the build up of sediment. In a previous comment, you mentioned that you like to leave the yeast cake as food for the brett. It also sounds like you usually top off with fresh wort, allowing all of the fermentation to happen within your solera vessel. How much sediment build up do you see over time and do you ever remove the sediment? Do you filter out all hot and cold break material before racking into the solera vessel? It just seems like this material would build up quite quickly.
When you say add fresh worth will the be boiled wort correct ? Can I boil it only 15minutes or need to boil it 90mins to get rid of DMS, or does it really matter since it ferments for long time will pulling stuff out ?
Adding a beer/dregs would contribute to the microbial diversity while adding wort would sustain it.
When pulling out 1/3 will that be ok to mix it with a sour (lacto) to give it a funk/sour character ? Then if yes, how can I stop the brett from going on if I bottle ?
@mcnewcp You certainly bring up valid concerns, I would say to just use your own judgement. After 2 years I recently racked all of the beer out and discarded the sediment, cleaned it out and racked new beer and the old beer back in. In a sanke keg I cant see the build up but in a carboy you definitely could. Brett can feed on dead Sacch cells, but I am sure there is a limit to how much of that trub is beneficial or detrimental to the beer I jjst dont know what the limit is.
@theQ Fresh wort as in a whole new batch of beer, so yes you boil for the standard 60-90 minutes. I am of the opinion that boil vigor is more important than length in driving off DMS, so I boil vigorously for 60.
Well in my example here the Brett and LAB have resided in your vessel for quite some time, so once you have a stable gravity you can package. If the gravity is stable you dont have to worry about the Brett overcarbing the bottles.
@Coff thank you. That makes a lot of sense.
Should I start with WLP655 or Wyeast 3763 Roselare ? I read that a bunch of people start with DME but that's more expensive - fast but expensive. What would be the OG for the start batch ?
BTW I did buy the book, it's a good read althou Solera coverage is limited.
Planning to start a sanke solera in the next few months. I am thinking of primary fermenting in carboys with Melange and then moving to sanke keg. I can see treating the topoff beer the same way. This may help prevent the trub buildup over time. Can the top off batch be a clean fermented beer since the bugs are in the solera?
If you're using Brett then you're in luck. Brettanomyces will consume ruptured yeast cells and their byproducts, so rather than autolysis you've got nutrient for your bugs!