Published on August 28th, 2013 | by Ruben Luyten1
The Solera system
Sherry has a unique and rather complex system of maturation using a large number of casks and fractional blending. This system is called solera and it is used in the production of all types of sherry, dry or sweet.
Soleras and criaderas
Barrels in a solera are arranged in different groups or tiers, called criaderas or nurseries. Each scale contains wine of the same age. The oldest scale, confusingly called solera as well, holds the wine ready to be bottled. When a fraction of the wine is extracted from the solera (this process is called the saca), it will be replaced with the same amount of wine from the first criadera, i.e. the one that is slightly younger and typically less complex. This, in turn, will be filled up with wine from the second criadera and so on. The last criadera, which holds the youngest wine, is topped up with a new wine named sobretabla. Taking away part of the wine and replacing it with the contents of other scales, is called rociar or to wash down.
A saca (taking out part of the old wine) and rocío (replenishing the casks) will usually take place several times a year, but the actual number may vary and specific figures are rarely disclosed. In Jerez, a Fino solera will be resfreshed two to four times a year. In Sanlúcar de Barrameda, due to the higher activity of the flor, a Manzanilla solera can easily have six to ten sacas a year. By law there is a maximum of 35% that can be taken out, but normally between 10 and 15% of the 500-550 litre capacity of the butts will be taken out and refreshed. A bit less in Manzanilla soleras. Note that it is not common for wine to be drawn off from all the casks of a solera at the same time – this is usually spread out over time.
Origins of the solera system
The solera system is believed to have originated in Sanlúcar de Barrameda in the second half of the 18th century. Prior to this, all sherries were bottled as añadas or vintages, a concept that was still widely in use until the 20th century. Some of the oldest soleras still in use are now at Osborne (laid down in 1790), El Maestro Sierra (1830), Valdespino (1842) and Gonzalez Byass (1847).
Organisation of a solera
Although a solera is usually represented as layers of casks stacked upon each other, with the solera level at the bottom of the pile, this is only the case for smaller soleras, or in bodegas where tours are being held. Usually barrels are stacked in blocks of casks rather than actual rows. We are talking about potentially hundreds of casks here, so sometimes a whole room is filled with just one criadera. Some of the largest soleras are even distributed over different buildings. Apart from the size of some soleras, there are two technical reasons behind this distribution: firstly, stability can be problematic when more than three or four casks are placed on top of each other, and secondly, it is better to place Fino and Manzanilla casks near the floor, where it is cooler, and oxidative types of sherry towards the top.
The number of tiers between the solera and the last criadera, varies largely and depends on the style of the wine and the preferences of the bodega. In general, Manzanilla and Fino soleras will have more criaderas than those of Oloroso and other oxidatively aged sherry, and in general older wines will have less criaderas. A typical Fino solera will range between three and seven criaderas. A Manzanilla solera will have at least nine criaderas, up to twenty.
Age of a solera
It is impossible to give the exact age of a wine that has been aged in a solera, as it is a blend of many vintages. It is only possible to give an approximate, average age of the wine. This is determined by the number of criaderas, the typical percentage of each saca, and the frequency of the saca. The combination of these factors defines the rotation of the total stock of wine and allows us to estimate the average age.
A wine bottled from a solera that was started ten years ago will have wine that is ten years old blended with wine that is nine, eight, seven… up to three years old. By law, sherry must reach an average age of 3 years before it can be sold, but in reality most are much older than that. When bottled, the age of all sherries must be assessed by a group of tasters from the Consejo Regulador, the governing body of the Jerez D.O., who will reject any wine if it deems to be too immature. They are also the ones who grant the VOS and VORS labels by assessing the flavour profile.
Note that sometimes the foundation year of the solera is mentioned on the label or even in the name (e.g. Gonzalez Byass Solera 1847), often leading to confusion with consumers who think this is the vintage of the wine.
While we said earlier that the highest criadera is topped up with young wine, premium soleras that hold very old wines will be washed down with soleras of similar style, i.e. already mature wine brought to a certain state of aging outside of the solera. This way, a solera can also be expanded by bringing casks to a required state before adding them to the system.
Purpose of a solera
The most significant result of the solera system is ensuring continuity and consistency. By blending multiple vintages, the possible variability of each year will be lowered and – after a certain amount of years - the bottled wine will maintain a constant average age. New wines are only gradually introduced to the system, and the influence of the new wine will disappear as it takes on the characteristics of the older sherry quite rapidly.
Furthermore, the solera system is essential for biological ageing under flor since every refreshment brings in young wine that contains the necessary micro-nutrients to support the yeast. Without this regular nutritional input, the layer of flor will die and the sherry will continue its maturation in an oxidative way. Note that the new wine is never poured in directly from the top, it is introduced in the cask gently and always underneath the film of flor without damaging it.
To sum up, a solera is essentially a never-ending ageing system, gradually but slowly growing older. Once mature and maintained in a proper way, it will show a unique personality, the identity of the solera.