The traditional Japanese fan used to cool sushi rice during preparation is the uchiwa.
An uchiwa is a rigid, usually round or oval hand fan made with a frame and a fixed surface, traditionally paper over bamboo. In sushi preparation, the chef fans freshly cooked rice after mixing it with seasoned vinegar. The moving air speeds cooling and helps excess moisture and vinegar aroma escape, producing rice with a glossy surface and a texture firm enough to shape.
The rice is commonly transferred to a hangiri, a broad wooden tub, and folded or cut with a shamoji, a rice paddle, while the uchiwa provides airflow. Cooling matters because hot rice can become overly soft and sticky, while fully chilled rice can lose the texture sushi chefs want.
Uchiwa is different from sensu, the familiar folding fan. Both are traditional Japanese fans, but the fixed uchiwa is especially practical in kitchens and is also used to fan charcoal for grilling. Outside cooking, uchiwa are associated with summer festivals, advertisements, and everyday cooling.