Fortified wine is wine that has had additional alcohol incorporated to it. First developed as a wine preservation technique, fortified wines now have their own category and fans. Brandy or some other grape spirit as well as additional sweetness is added, giving the fortified wine an alcohol content between wines and spirits. One type of fortified wine is port. The higher alcoholic content in port is achieved through adding grape spirit to stop the fermentation process. This also maintains a higher sugar content. Vintage ports are made only during excellent seasons and left in wood to mature for two years. Other ports are matured in wood for different time spans. Sherry is another type of fortified wine that comes as either a deep Oloroso or light Fino. Sweetness is added to either style before bottling for sweet sherry. Sherry is aged in wooden casks or butts and blended in a system called a solera. This system involves adding older wines to younger wines over a period of several years which allows the younger ones to become more like the older ones in flavor. The intensity of the fortification in sherries depends on whether they develop a yeast bloom called a flor while in the butts. Those that do, become Fino sherries and are fortified with brandy. Olorosos are fortified more intensely than Finos. Madeira is a dry and sweet fortified wine that was sent on sea trips to the tropics. During these long durations, its flavors were softened by the warm temperatures. Today, heat is a key factor in the aging process of the wine. Expect the cheaper wines to have been heated only for about three months while the expensive madeiras are heated less intensely for almost a year.