Nøgne Ø Burthen is a spontaneously fermented sour ale with grapes from Tromøya outside Arendal. Morten and Ed have been picking from what is perhaps Norway's largest wild-growing grape tree. The beer has fermented on the natural yeast from the grapes for 30 months. It has developed a fresh acidic taste and a crush dry mouthfeel. Brewed with 100% Norwegian malt.