thumb|[[Sherry solera]]
Solera is a process for aging liquids, such as wine, beer, vinegar and brandy, by fractional blending, so that the finished product is a mixture of ages, with the average age gradually increasing as the process continues over many years. The purpose of this labor-intensive process is the maintenance of a reliable style and quality of the beverage over time.
Solera means "on the ground" in Spanish, and refers to the lower level of the set of barrels or other containers used in the process. The liquid is traditionally transferred from barrel to barrel, top to bottom, with the oldest mixtures being in the barrel right "on the ground". Nowadays, the containers are not necessarily stacked physically in this way but merely carefully labeled.
Products which are often solera aged include Sherry, Madeira, Lillet, Marsala, Mavrodafni, Muscat, and Muscadelle wines; balsamic vinegar, Commandaria, some vins doux naturels, and sherry vinegars; Brandy de Jerez; beer; rums; and whiskies. Since the origin of the process is the Iberian Peninsula, most of the traditional terminology is in Spanish and Portuguese.
Solera process
thumb|A diagram of the 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). A group of one or more containers, called scales, criaderas ('nurseries'), or clases are filled for each interval. At the end of the interval after the last scale is filled, the oldest scale in the solera