Solera by the producers of sherry. In a Spanish sherry "solera", the vintner may transfer about a third of each barrel a year. A solera sherry has to be at least three years old when bottled. A quite similar process is called sostrera, used to produce fortified wines in the Mediterranean regions of France. In Sicily, where Marsala wine is made, the system is called "in perpetuum". Solera vinification is used in the making of Mavrodafni ("Black Laurel"), a fortified red dessert wine made in the Northern Peloponnese in Greece. Exceptional "Mavrodafni" vintages are released every 20 or 30 years: they
Fortified wine grain, sugar beets or sugarcane. Regional appellation laws may dictate the types of spirit that are permitted for fortification. For example, in the U.S. only spirits from grapes may be used. The source of the additional alcohol and the method of its distillation can affect the flavour of the fortified wine. If neutral spirit is used, it will usually have been produced with a continuous still, rather than a pot still. When added to wine before the fermentation process is complete, the alcohol in the distilled beverage kills the yeast and leaves residual sugar behind. The end result is a