In Japan, and especially in West Honshu, making vinegar is an ancient ritual which made its way to Japan from China some 5000 years ago. Traditionally it was made using barley or rice, later also sake, and kept in clay pots for fermentation via the Japanese fungus Aspergillus Oryzae. The pots are kept outside for around 3-6 months and regularly hand-stirred to assist the slow, steady fermentation process. The starch is converted to fermentable sugars which then form ethanol. The presence of naturally occurring yeasts do the rest.