For those that are unfamiliar, a Solera by definition, is a a process used traditionally in sherry, vinegar and brandy production, however, can be used for beer. An oak barrel is filled and aged and every so often a portion of the volume is removed and packaged. That volume is then replaced with new beer or wort and provides the brewer with an ever evolving project.

I have become more intrigued with sour beers and brewing and have since started a small sour program over the past few weeks/months. Since this barrel has sat empty for the past while, I wanted to incorporate it into this system as a solera. After brewing Counting to Infinity Saison and enjoying drinking it even more, I wanted to try the more traditional approach to brewing farmhouse beers with mixed cultures (mostly sacchromyces and brettanomyces) in oak to achieve that rustic and funky saison character.

If you have been following me over the past year or so, I had purchased a used bourbon barrel from a local distillery (River Hill Distillery, Luray, VA) and aged a barleywine in it for 2-3 months. Since packaging that batch in kegs almost exactly a year ago, the barrel has sat in my basement since, empty and exposed. Luckily, the heads hadn’t dried out much and the barrel still smelled clean (with a nice bourbon character remaining). Feeling a little iffy on whether to spend the money purchasing grain and such for 15 gallons of higher ABV beer to refill it and risking contamination, I decided to attempt to clean, sanitize and fill with a holding solution until I have beer ready for filling. Below is the exact process I used to achieve this, using a multitude of internet and podcast sources.

Inspecting the Barrel

My first step before even embarking was to ensure that the barrel was in suitable condition for long-term storage and culture harboring. The bung had been tightly placed for the entirety of the year (I’m usually really nosey about things so I’m surprised I didn’t fiddle with it more). I used some vice grips to remove it and inspected the inside of the barrel for mold, of which I didn’t see any. As I stated before, I smelled the inside of the barrel for musty, vinegary, or overly acetic qualities (usually nail polish aromas of ethyl acetate) from aerobic acetobacter bacteria. The barrel smelled clean, with a remaining bourbon component, no indication that it had even been filled with a batch of beer once in the past. Off to a good start! Now to attempt to rinse/clean the barrel of any dust and debris that may have entered through the staves or heads while simultaneously checking for large leaks.

Light Rinsing and Cleaning of the Barrel

If there was significant mold or residue from the previous fill and subsequent neglect, a more intense cleaning procedure would be prescribed, involving removing the hoops, then one of the heads, and brushing out the interior of the barrel or using a power washer to get deeper into the wood. Since the inspection of the barrel went well, and the condition of the interior seemed appropriate, I decided a light rinsing would be adequate to remove some excess charcoal, dead yeast and trub from the previous batch of beer, etc.

Initial Filling and Swelling

I filled the barrel with about 2-3 gallons of cool tap water, sloshed it around the interior of the barrel, and dumped its contents. I repeated this step about 2-3 more times, just to ensure most of the debris was cleared. I then filled the barrel to the brim with the same temperature water to check for leaks at the heads or between the staves.

Pictured above are both of the heads after filling with cold tap water. They didn’t leak at a particularly rapid rate, but it was significant enough that if it were to be beer instead of water, and in the cellar as opposed to outside of the patio, I would have been in a bit of trouble. Needless to say, I allowed the barrel to sit full of water for about an hour, maybe a little less, and the leaks changed from a steady thin stream to a slow drip. All in all, with this step the barrel lost about 1/2 gallon of water in total.

As you can see with the top left photo, there was minimal leaking through the staves. The small wet spot seen was the only place on the entire surface of the barrel that had any indication of a leak, which ended up sealing fairly quickly and by the time I returned after the initial hour of swelling, the wet spot had vanished, indicating that it was sealed.

Holding with Hot Water to Sanitize

After the hour holding time with cold water, the barrel was dumped completely and filled with boiling water that was heating while the initial swelling phase was taking place. This will begin the sanitization of the barrel, in addition to completely swelling the heads and staves with the help of heat expansion.

I let the barrel sit with the boiling water for 1.5 hours. The length of time is arbitrary however, I just happened to be busy with other daily chores. With a temperature probe placed in the center of the barrel, the temp initially after filling read 205F, and dropped to 194F when I returned. Without getting too much in depth, I had read an article on the Milk the Funk Wiki page that indicated heat sanitation of barrels at 60C (140F) for 19 minutes eliminated the yeast populations up to a log count reduction of 8, meaning that a significant amount of the wine spoilage organisms Brettanomyces/Dekkera bruxellensis (coincidentally the organism that I will be introducing back into the barrel in secondary fermentation) were killed resulting in a properly sanitized barrel for long term storage with an appropriate holding solution. I may have went overboard on the heat and holding time, but there shouldn’t be much recourse on the barrel’s integrity or functionality considering it is common practice to steam the barrels to santitize them, having them reach a similar internal temperature for a given length of time. The barrel was then CAREFULLY emptied and the holding solution was prepared.

Preparation and Instillation of the Holding Solution

Since I don’t intend on filling the barrel for a few months, I wanted to store the barrel full with a holding solution of potassium metabisulphite and citric acid to keep it swollen and to discourage the growth of bacteria, yeast and molds. According the the barrel section of the MTF Wiki, and after plenty debate, Andrew Zinn from Wicked Weed Funkatorium indicated that 0.3 grams of potassium metabisulphite (campden tablets) per liter of barrel volume (~ 3.8 liters/gallon) was an appropriate concentration to inhibit microbial growth and limit residual sulfur character in the barrel after emptying. The general consensus for citric acid remained at around 1 gram per liter of barrel volume.

The barrel was taken into the cellar empty, and filled on my fancy homemade barrel rack made from old fence posts (I will make a better one with casters on it later). I filled the barrel about 1/3 full with cold tap water, added the components (campden tablets were crushed finely of course) to the barrel and mixed well for about 1-2 minutes. I then topped off the full barrel volume and plugged the bung.

Hopefully within the next 1-2 months I will have brewed 20 gallons of moderately strength saison, using 15 gallons for the initial fill and the other 5 gallons for top-up as needed. Stay tuned for updates!

Cheers!