The Traditional balsamic vinegar at Vine and Grind is made in Reggio Emilia and Modena, Italy, using traditional methods.
Grape must (from whole pressed grapes that are late harvested and include the juice, skin, seed and stem) are the start of traditional balsamic vinegar. The must is then cooked over a direct flame until concentrated by roughly half, then left to ferment naturally for up to three weeks, and then matured and further concentrated for a minimum of 12 years in a "batteria," or five or more successively smaller aging barrels. These barrels are made of different types of wood such as oak, chestnut, cherry, juniper, and mulberry, so that the vinegar can take on the complex flavors of the casks.
Once a year the vinegar is bottled from the smallest cask in the sequence. Each cask is then topped up with vinegar from the next cask up, with the largest cask getting filled with the new yield. None of the casks are ever completely drained. The vinegar gets thicker and more concentrated as it ages because of evaporation that occurs through the walls of the barrels. The vinegar from the smallest barrel will be much thicker than the liquid in the successively larger barrels.
Because of the multi-barrel process, it takes complex math to gauge the average age of the bottled product, so instead a tasting commission of five expert judges convenes to taste the vinegars and determine an appropriate grade, and no age is printed on the label. In Reggio traditional balsamics are capped according to their vintage. Red cap (12-year vintage); Silver cap (15-20 year vintage); or gold cap (20-25 year vintage). In Modena there's just affinato, with a white cap, or extra vecchio, with a gold cap.