Kai and Kaburagai (sake-brewing stirring paddles)

A kai (櫂) is a tool used in sake brewing to stir the shubo (yeast starter) and the moromi (fermentation mash). It is important for mixing liquid and solids evenly, and is used mainly in large tanks and vats. There are several types of kai, and how each is used depends on its shape and construction. The kaburagai (蕪櫂, also read kaburakai) has a trapezoidal board at its tip and is used mainly for stirring the moromi. The flat tip stirs the liquid thoroughly, allowing an even mixture. The bokai (棒櫂) is shaped like a boat oar and is used mainly when stirring a wide area. This shape creates a current as it moves, which makes it well suited to mixing effectively in a large tank. The onikai (鬼櫂) is a rod-shaped tool that thickens from the grip toward the tip, and is used when powerful stirring is needed. Its shape allows it to work effectively even when the moromi has become stiff. Stirring with these tools makes fermentation more even and contributes to improving the quality of the finished sake.