W – as in Whisky Solera

What does Solera or the Solera system mean?

The Solera system is a complex process used for the traditional aging of Sherry. The vast majority of Sherries are aged in this system, also known as the "Criadera & Solera System". The word Solera, by the way, is derived from suelo, the Spanish word for floor.

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Where can you see the Sherry Solera system?

Ideally, directly on site in Andalusia, in one of the many warehouses of southern Spanish bodegas.

What exactly is Sherry?

Sherry is a white wine fortified with brandy, aged in oak barrels – mostly American white oak, but also European oak – or even in chestnut wood barrels. Sherry is a controlled designation of origin and is concentrated in a small region of Andalusia in southern Spain. Only nine towns have vineyards within their respective municipal districts that belong to the controlled designation of origin D.O. Jerez. Among them are the three towns of Jerez de la Frontera, El Puerto de Santa María, and Sanlúcar de Barrameda, which form the famous Sherry Triangle.

How does a Solera system work?

The Solera system is a dynamic system consisting of several barrels. These are usually stacked on top of each other, often in a pyramid shape. The wine therefore does not age in just one single barrel, but goes through various stages in its aging process – thanks to regular transfers from top to bottom in the barrel pyramid – which consist of groups of barrels with increasingly older wine.

How is a Solera system structured?

The system generally consists of three or four rows of stacked barrels, with each row representing a different stage of the aging process. The bottom row, called the Solera because of its proximity to the floor, is the last stage of the aging system and contains the oldest Sherry. Up to a third of the content is drawn from these barrels for bottling. The rows of barrels above contain the various Criaderas; the higher the row, the younger the wine a Criadera contains. The row immediately above the Solera is the first Criadera, and the wine in its barrels is younger than that of the Solera. Above this row is the second Criadera with an even younger wine and so on. It is important to mention that the individual barrels in a Solera system are not connected to each other, but are merely loosely stacked side by side and on top of each other.

Is the number of rows in the Solera system limited?

No. There can also be a third, fourth, fifth Criadera or even more rows. There is no specific limit to the number of rows in the Sherry Solera system. However, if the Solera system consists of more than three or four rows of barrels, the Criaderas must be stacked in more than one pyramid to prevent the bottom row from bearing too much weight and, in the worst case, even bursting the Solera barrels.

Why does St. Kilian have a Whisky Solera?

The first trip of our Master Distillers Zoltán Fodi and Mario Rudolf to Andalusia in 2019, with visits to various wineries and coopers, was the trigger for their enthusiasm for Sherry casks, the Spanish bodegas and the Solera system. With these fascinating impressions, the idea quickly matured in them to transfer the sophisticated and complex Sherry Solera system to the aging of single malt whisky.

Which Whisky Soleras does St. Kilian have?

We have set up two independent Solera systems for aging single malt whisky. In June 2020, we started our Whisky Solera by St. Kilian mild, which initially began with cask-aged, non-peated spirit. In October of the same year, the Whisky Solera by St. Kilian peated was then started. This began with peated, cask-aged spirit.

How is the mild Whisky Solera at St. Kilian structured?

The Whisky Solera by St. Kilian mild (unpeated) consists of three rows of barrels, each with seven barrels. The bottom row, the Solera, is made up of certified seasoned Pedro Ximénez Barrique barrels (225 liters) from Bodega Ximénez-Spínola in the D.O. Jerez. For the overlying first Criadera, 225-liter medium Sherry barrels, also from Bodega Ximénez-Spinola, are used. For the top second Criadera, we use certified seasoned first-fill Manzanilla Hogsheads with a capacity of 250 liters.

Which barrels make up the peated Whisky Solera?

For the bottom row of our peated Whisky Solera, as with the mild version, 225-liter, certified seasoned Pedro Ximénez Barrique barrels from Bodega Ximénez-Spínola are used (six barrels). The first Criadera above consists of two Amontillado Bodega 500-liter Butts (each 20 years old) and one 500-liter, 30-year-old Fino Bodega Butt. Finally, three seasoned Oloroso Butts (500 liters each) form the top row of barrels, the second Criadera.

How was the mild Whisky Solera started?

For the mild Solera, in June 2020, one-year-old spirit, matured in charred (Char Level 4) 190-liter Virgin American Oak casks, was filled into the casks of the second Criadera. Their contents were then completely transferred to the casks of Criadera one below in January 2021, and the thus empty casks of Criadera two were refilled with now two-year-old spirit, matured in charred 190-liter Virgin American Oak casks. One year later, in January 2022, we transferred the entire contents of the casks of the first Criadera into the Solera casks, transferred the complete contents of the second Criadera into the emptied casks of Criadera one, and refilled the empty casks of Criadera two with now three-year-old single malt whisky from the charred 190-liter Virgin American Oak casks.

How was the peated Whisky Solera started?

The principle is the same as for the mild Whisky Solera. However, it was only in October 2020 that the casks of Criadera two were filled with one-year-old, peated spirit, matured in charred (Char Level 4) 190-liter Virgin American Oak casks. The transfers to the other rows of barrels took place - analogously as described above - in October 2021 and February 2023 respectively. Only for refilling Criadera two, a two-year-old, peated spirit, matured in ex-Bourbon casks (Jack Daniel's), was used from October 2021. In February 2023, the casks of Criadera two were then refilled with three-year-old single malt whisky, matured in ex-Bourbon casks (Jack Daniel's).

What's next for the Solera Systems at St. Kilian?

From 2024 onwards, approximately 30% of the volume (about 400 liters) will be drawn from the Solera barrels of the mild Whisky Solera every spring and bottled in our 0.5-liter pot still bottles. The missing volumes will be replenished from the overlying barrel rows, as described above. The barrels of the uppermost Criadera two will then always be topped up with at least three-year-old single malt whisky matured in ex-Bourbon barrels (Jack Daniel's). The same applies to the peated Whisky Solera. Here, the first withdrawal from the Solera barrels (approx. 30%) and bottling in 0.5-liter pot still bottles already took place in autumn 2023. Subsequent bottlings will then always be released in the autumn of the respective year.

How do you calculate the age of a Solera-aged whisky?

Given the procedure of the Solera method, the age of a single malt whisky aged in it is inevitably expressed as an average and essentially corresponds to the rotation of the total stock in each aging system. This average age depends on the number of barrel rows that make up the Solera system, the proportion of whisky drawn from the Solera barrels, and the frequency of these draws. Provided that the system runs for at least three years, so that the spirit can be called whisky, and at least three-year-old whisky is always refilled into the casks of Criadera two, the age of the Solera-aged single malt whisky is calculated as the quotient of the volume of all casks in the Solera system divided by the volume drawn in one year. In 2032, our Whisky Solera, whether mild or peated, will reach an average age of 10 years.

How complex is this Solera aging process for whisky?

Aging single malt whisky in our two Whisky Soleras by St. Kilian is extremely complex. It requires a lot of work and craftsmanship and is also associated with a great deal of effort. This is because in Germany it is not permitted to simply remove the required volumes from the barrels using a pump. Due to the regulations of German customs, we have to completely empty each row of barrels, process every removed whisky for tax purposes, and only then are we allowed to put it back into the respective barrels. So it's a very elaborate procedure, combined with a lot of bureaucracy and documentation. But we are convinced that the quality of the whiskies and the success will prove us right.

Why go to all this enormous effort?

Because St. Kilian has been known for innovation and experimentation from the very beginning. And because we are so enthusiastic about Sherry cask-aged whisky, and want to offer our customers and fans exceptional products. The Solera system will build specific aromas that will add up and intensify, so that we will obtain an extremely complex and multi-layered single malt whisky according to our ideas. The exciting thing about this process is that our fans can follow and taste the development of the Whisky Solera by St. Kilian live every year with the corresponding mild and peated bottlings.

Are there other whiskies aged in the Solera system?

Yes. There is at least one American distillery that ages one of its Bourbon whiskeys in the Solera system. In addition, there are Australian and also Swedish single malt whiskies that are aged using this method.

Are other spirits or even wines also aged in the Solera system?

Absolutely. For example, Spanish brandy, Brandy de Jerez, is also aged in the cascading process. There are also some rum distilleries that age their distillate obtained from sugar cane in a Solera system. Similar to Sherry, the Solera system is also used as an alternative aging method for some Málaga and Madeira, these famous dessert wines. And high-quality wine vinegar is often also a product of this special aging process.