In Jerez de la Frontera’s González Byass bodega, row upon row of 600-litre oak butts sit in purposeful formation. They are filled with myriad styles of Sherry, which are blended and aged by master blender Antonio Flores using the drink’s signature solera system. Derived from the Spanish word suelo (meaning ‘floor’ or ‘ground’), soleras have been used in Sherry-making since the 18th century. Barrels are stacked in a pyramid of criaderas (rows), with the oldest liquid at the bottom and the newest at the top; over time, these casks carrying different ages of liquid are married together.
This is an important process when it comes to working with wines. By using a solera system, different vintages can be combined together to achieve consistency. ‘The solera system is a type of fractional blending,’ explains Dawn Davies MW, head buyer at The Whisky Exchange. ‘In theory, you have a very consistent product coming out at the end of it because you should be blending away individual differences of things like terroir and cask. This is why the Sherry region employed the system: to remove any differences and to give their customer the same flavour profile and product year on year in volume and at a sufficient quality.’
The concept of the solera system has been used in different guises around the world – from the production of balsamic vinegar, to the making of beer. But the term has also made its way into the vernacular of the spirits world. From Scotch and American whiskey, to South American rum and Japanese awamori, the word ‘solera’ is increasingly being seen on bottles and as part of a brand’s storytelling. It is a term that conjures romanticism and tradition; its pyramids represent the skill and the science that make this time-honoured process work so successfully. Yet how it positively affects spirits is a looming question that isn’t always easy to answer. Controversies over accompanying age statements and their accuracies also abound.
Arguably its most obvious and traditional application in spirits comes from close to home, in Spanish brandy – Brandy de Jerez, Lepanto and Soberano. ‘These brandies follow the same system of solera and criaderas as our Sherry and using barrels that have previously contained Sherry,’ explains González Byass senior brand manager Amanda Baxter. ‘It is within these systems that the brandy develops its great complexity and character, marked by the infusion from the Sherry casks. We have been using this barrel system for over 100 years, and the generational knowledge passed down ensures the highest quality is retained.’
When it comes to other spirit categories, while the term ‘solera’ might not perfectly match the method of Sherrymaking, distilleries have adapted the technique to suit their own production needs and capabilities. Take rum distilleries, especially those in South and Central America (where Spanish influence forms part of their history), which are using their own signature solera systems. Venezuela’s Santa Teresa 1796 is possibly the best-known example, where the concept is used to integrate some of its first 1796 cask into every bottle. Its maestros blend a range of different styles of their rums – aged, light, heavy and pot still – in a tank that is fed into the top of its four-tier solera system. The bottom criadera is then drained, added to its mother rum, vatted and bottled. It’s worth mentioning that these barrels are changed each time a new recipe is made, contrary to the traditional solera method.
Elsewhere, why and how these solera systems are used in rum-making isn’t always so obvious. And legalities over age statements in solera rums has been a huge source of contention. With the law having changed in the EU in 2021, brands are required to mark the age statement in reference to the youngest rum in a blend – whereas those using criadera ageing had instead historically been adding the age of their solera system to their labels as an age statement.
Whisky distilleries, especially in Scotland and the US, are also talking about soleras. Over at Speyside’s Glenfiddich, its fifth malt master David Stewart was one of the first in Scotch to play with the method, having been inspired by witnessing the magic of the system on a trip to Spain. He introduced a custom built solera vatting system to create its 15-year-old single malt, which is aged in ex-Sherry and bourbon casks. Instead of using Sherry’s pyramid system, the ex-American-oak spirit is finished in new American oak before casks are introduced to each other in the solera vat for marrying. (When the casks are emptied into the solera vat, by law they are not maturing further.)
This is a continual mixing process, and only half the contents are emptied at a time before more casks are added; like the bottom row of a Sherry solera system, it is never fully emptied, which means there is still liquid remaining from its first fill in 1998. Once the whisky has spent time in the vat, it is moved into marrying tuns. The result is a showcase in the art of consistency and a nod to the distillery’s lineage. The fact the distillery has 99 marrying tuns dedicated to this single expression is testament to its popularity.
Not all whisk(e)y-makers are aiming for consistency with the concept of solera, though. At Oregon’s Westward Distillery, master blender Miles Munroe has built a 21-barrel solera system to make its Milestone release. A small amount of the whiskey is removed each year and replaced with something else from the barrel house. Instead of maintaining consistency, this solera is designed to make the annual release evolve with each passing year. On the other foot, New York’s Hillrock Estate is doubling down on the way it honours the Spanish ageing technique, through the use of a four-tier solera system, with a bottom row – effectively, the spirit’s final fill – of Oloroso Sherry butts.
While ‘solera’ may be the closest and clearest way of explaining all of these processes, Davies is sceptical as to whether using the term is having the kind of impact on spirits as it does on wine – and whether some of these soleras are in fact soleras at all. Of course, the other key benefit of the original solera system is providing the perfect conditions for biological ageing, with maker’s encouraging the growth of a distinctive layer of yeast – named flor – within the pyramid’s wine barrels, which can give a Sherry its nuttier flavours while also forming a protective layer against oxidation. This technique becomes redundant in the making of spirits. ‘In the case of Fino, for example, the adding of young wines helps keep the flor alive with the nutrients it needs,’ explains Davies. ‘In this case, wine is more complex and will be affected more intensely by oxygen than whisky or rum.’
There’s also the M-word to consider: ‘Solera systems have a nice marketing ring to them, much sexier than “perpetual ageing”,’ says Davies. ‘Sadly, I also think [spirits brands] are using terms they don’t fully understand, and they haven’t taken the time to learn why the solera is so important to wine ageing and what it really means and what is the actual physical process.’
Buying into the idea that spirits really are using solera systems is something that should come with an element of research. ‘It’s a physical system of barrels, and the movement of the liquid between them takes a huge amount of time and care to keep up… You should be able to see it,’ says Davies.
So while the idea is quite romantic, it seems a solera being used for both process and outcome in spirits is on a rather steep sliding scale. Is it marketing? Perpetual ageing? Neither – or both? Seeing, it seems, is believing.
