Weak water (yowai mizu)

Weak water (yowai mizu) refers to brewing water that slows the activity of the moromi (fermentation mash) during fermentation. Because it contains little of the components that support fermentation, such as potassium, magnesium, and phosphate, the yeast is restrained and fermentation proceeds slowly. This characteristic can influence the style and flavor of certain sakes. Brewing with weak water allows flavors to be drawn out with care, but it calls for careful technique and experience in managing fermentation.