When water has penetrated from the outside of a rice grain into the central structure of sakamai (rice for brewing sake) where starch content is high (according to the language of toji and other workers in brewery "mentama" (literally, "eyeball"), the rice grain become literally transparent.
水が、米粒の外側から、中心部の酒米構造（杜氏蔵人言葉では「目んたま」）と呼ばれるデンプン質の多い部分へ浸透していくと、米粒が文字通り透き通ってくる。