A solera is a series of barrels used for aging liquids. The solera is a process for aging liquids by fractional blending in such a way that the finished product is a mixture of ages, with the average age gradually increasing as the process continues over many years. A solera is literally the set of barrels or other containers used in the process. In the solera process, a succession of containers are filled with the product over a series of equal aging intervals (usually a year). One container is filled for each interval. At the end of the interval after the last container is filled, the oldest container in the solera is tapped for part of its content, which is bottled. Then that container is refilled from the next oldest container, and that one in succession from the second-oldest, down to the youngest container, which is refilled with new product. This procedure is repeated at the end of each aging interval. The transferred product mixes with the older product in the next barrel. Our eight-barrel solera is mainly made up of French oak barrels, but our two finish or final barrels are Italian chestnut.
This process ensures that each year’s bottling of Bannerman’s Castle Amber Cream tastes like the one before it. It guarantees consistency of quality and taste. This is a time-honored system for making sherry, first developed in Jerez, Spain. The word “sherry” is an anglicization of Jerez.
In our sherry solera at Paperbirch, no container is ever drained, so some of the earlier product always remains in each container. The age of product from the first bottling is the number of containers times the aging interval. As the solera matures, the average age of product asymptotically approaches the initial age, divided by the fraction of a container which is transferred or bottled. Currently it takes new or young wine 4 ½ years to travel through our system, but with additional barrels to be added, that time will increase.
For instance, suppose the solera consists of four barrels of wine, and half of each barrel is transferred once a year. At the end of the fourth year (and each subsequent year), half the fourth barrel is bottled. This first bottling is aged four years. The second bottling will be half four years old and half five years old (the wine left in the last barrel at the previous cycle), for an average age of four and a half years. The third bottling will be: one fourth wine that was six years in the fourth barrel, one fourth wine that was four years in the third barrel and one year in the fourth barrel, one fourth that was three years in the third barrel and two years in the fourth barrel, and one fourth that was two years in the second barrel, one year in the third, and one year in the fourth: average age five years. After 20 years, the output of the solera would be a mix of wine from 4 to 20 years old, averaging slightly under 8 years. The average age asymptotically converges on eight years as the solera continues.
At Paperbirch, the output of the solera is the fraction of the last container taken off for bottling each cycle. The amount of product tied up in the solera is usually many times larger than the production. This means that a solera is a very large capital investment for a winemaker. If done with actual barrels, the producer may have several soleras running in parallel. For a small producer, a solera may be the largest capital investment, and a valuable asset to be passed down to descendants.
The sherry produced at Paperbirch using the solera method, cannot formally have a vintage date because it is a blend of vintages from many years.
