Wines are aged in oak barrels in order to intensify or subdue various flavors and ultimately bring about a more complex product. Cinnamon, graphite, cedar, coconut, vanilla, hay, and clove are just some of the flavors that can be imparted into a wine from an oak barrel. But are all barrels the same, or are there differences that affect the flavor?

The type of oak used to craft the barrel is very important and will impart specific flavors to the wine. Most wine barrels are made from either French or American oak, but some are made from oak imported from Russia or other places in Eastern Europe.

Barrels are also fired on the inside in a process called "toasting," with the amount of char complementing different grape varietals and desired wine styles. The more char, the faster the oak flavors make their way into the wine. Additionally, the tightness of the wood's grain will affect the speed of the flavor transfer, with tighter grained wood taking longer. Thus, it's important for the winemaker to select barrels of the proper specifications for the style of wine he or she would like to make, and then age it for a length of time appropriate for the style (typically between a few months to two years).

Depending on the cooper (who is the manufacturer who constructs the barrel) and the type of oak used, barrels can cost several hundred dollars all the way up to about $1,500. Each time the barrel is used to age a wine, it loses some of its flavor, so some winemakers will use a barrel just once (when the flavor compounds are most intense), while other winemakers may use a barrel as many as five times or more, although at that point the barrel typically becomes "neutral" and imparts very little flavor. Often winemakers will age their wine in barrels of various ages in order to reach a specific desired flavor.