The Solera Aging Method
Photo from Hillrock Estate Distillery. Source: www.thewanderingeater.com
There are currently two bourbons on the market which were aged by the "solera" method (Blade and Bow and Hillrock). If you've seen the term "solera" and wondered what it meant, here's a layman's explanation, some photos, and interesting videos of "solera" in action.
Solera is Spanish for "on the ground" and refers to a process through which distillers, vintners, and brewers blend their product to ensure consistency. In the case of bourbon, white oak barrels are stacked on top of each other. The bottom layer of barrels, the solera, is always filled with the oldest juice, and the upper rows ("criaderas") are filled with younger whiskey. Over time, bourbon is removed from the solera row and blended with younger bourbons. Whatever percentage was taken from the solera is replaced with bourbon from the younger barrels and the same amount taken from those barrels will be replaced with new whiskey. The process repeats.
The solera method, developed by the Spanish and Portuguese, is common in Scotch, beer, wine, sherry, port, and rum making, but obviously uncommon in the United States where most spirits go through a static aging process (e.g. the Old Rip Van Winkle 10 Year label declares "asleep many years in the wood").
Solera aging allows mega-coprorations like Diageo to market a product like Blade and Bow as containing Stitzel-Weller bourbon. In reality, a tiny portion of Blade and Bow contains Stitzel-Weller bourbon. You may have some 20+ year old bourbon taken from a "solera" barrel, but the rest of the blend may be 10-year-old or even 2-year-old bourbon from higher "criaderas." Whether or not the aging method provides consistency in bourbon is yet to be seen, as Blade and Bow and Hillrock are new products, whereas many European solera-aged spirits come from truly historic distilleries. Comment below and let us know what you think!