Whiskey barrel maturation
Aging in barrels is a determining process for the different flavors of a whisky. Independent bottlers look for the best whiskey casks in order to "rerack", i.e. transfer the whiskey into other casks to add another dimension to the aromas.
Scotch whiskey is aged in oak barrels that have usually held another spirit or wine before. The reason for this is that the new oak can overpower and overpower the delicate flavors. These are mostly ex-bourbon casks from the USA and ex-sherry casks from Spain. There are many styles of sherry that can be used on cask, including ex Amontillado, Fino, Olorosso, Palo Cartado or Pedro Ximinez.
Cask finishing in wine casks and other spirits casks has become very popular in recent years. Here the whiskey is transferred to a different cask to complete its maturation and gain complexity by the cask which was maturing another wine or spirit. Although all stages of the distillation process are important for great whiskey maturation in oak barrels, it is widely considered to be the most influential part of whiskey making with 60-80% of the final aromas and flavors coming from the time spent in the barrel during maturation.