Featuring ripe, local apricots, nectarines, and plums, the brewers started by spontaneously fermenting the fruit using carbonic maceration. That’s a type of fermentation that occurs from the inside out, using carbon dioxide instead of yeast, and ultimately making for a juicier brew! Then they blended all that nectarous stone fruit and let it ferment a second time, with yeast, in barrels of Grimm’s aged Sour base.