Iwaawa (rock foam stage of moromi)

Iwaawa refers to a distinctive state of foam seen on the moromi (fermentation mash) of sake during fermentation. In this state, the water-like bubbles gradually grow larger and the whole surface swells upward, giving the impression of cracked or split rock. Iwaawa is a type of high foam (taka-awa) seen in the early stage of fermentation, and marks the period when the bubbles forming in the moromi increase rapidly and take on a characteristic shape. The movement and shape of this foam are an important indicator that fermentation is progressing.