Water is indispensable throughout the process of making soba.
The flavor of soba depends on the buckwheat flour and water used, and using water of fine quality when kneading the dough helps it develop an appropriate stretchy consistency, making it easier to roll out the dough after it has ripened. When soba noodles are boiled, nutritive elements in the flour, such as vitamins and minerals, escape into the water. This water, called soba-yu, is especially tasty if good water is used. Soaking soba in plenty of cold water immediately after boiling gives it a firmer al dente texture. Thus, fine water is indispensable in the process of soba making, and it is generally agreed that delicious soba is made where such water exists.