**Solera** is a process for

aging liquids such as

wine,

beer,

vinegar, and

brandy, by fractional blending in such a way
that the finished product is 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.

Products which are often *solera* aged
include Sherry, Madeira, Marsala,
Mavrodafni, Muscat, and Muscadelle wines; Balsamic, Commandaria, and Sherry vinegars; Spanish brandy; and
rums.
## Solera 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.

No container is ever drained, so some of the earlier product always
remains in each container. This remnant diminishes to a tiny level,
but there can be significant traces of product much older than the
average, depending on the transfer fraction. In theory traces of
the very first product placed in the

*solera* may be present
even after 50 or 100 cycles.

## Aging

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.

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.

## Solera production

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.

Wine produced from a solera cannot formally have a vintage date
because it is a blend of vintages from many years. However, some
bottlings are labeled with an age for marketing reasons. It is
unclear whether such age indications denotes the average age, or
the age of the oldest batch.

## Solera in different countries

This process is known as

*solera* in Spanish, and was
developed by the producers of sherry. In a Spanish sherry

*solera*, the vintner may transfer about a third of each
barrel a each year. A

*solero* sherry has to be at least
three years old when bottled.

[32153]
In

Sicily, where Marsala wine is made, the
system is called

*in perpetuum*.

Vintners
in Rutherglen,
Australia produce fortified muscat-style and Tokay-style wines using the *solera*
process.
Glenfiddich, a Speyside distillery in
Scotland has a 15
year old whisky that uses a process that is
similar to the solera process. The whisky is labelled as
their "15 year old single malt Scotch Whisky".

## Possible *solera* abuse

Italian labeling
laws permit blended vinegar to be labeled with the age of the
oldest vinegar in the blend. Some balsamic vinegar producers
have established

*solera* aging facilities, and claimed the
age of the entire

*solera* as the age of the vinegar
produced. In the case of the more strictly-controlled and more
expensive vinegars, such as

*aceto
balsamico tradizionale*, this labelling practice is not
permitted.

## References

## External links