The hardness of water varies from source to source. It is determined by the concentration of certain minerals, especially magnesium, calcium and calcium carbonate. It is measured in parts per million (ppm). At less than 60 ppm, the water will be considered very soft; in Japanese, it is called nansui 軟水. On the other hand, if it contains more than 120 ppm, it will be qualified as hard; it is called kôsui 硬水.
Thanks in particular to its relief, abundant precipitation and accumulations of snow, Japan is above all endowed with soft water.
Even Nada’s kosui in Hyogo Prefecture is no harsher than the water from the Montreal aqueduct.
Hardness will not necessarily establish the succulence of the sake. It’s up to Toji to harness the full potential of his water.
Relatively hard waters like that of Nada, for example, thanks to their high magnesium content, boosts fermentation, makes it more vigorous and fastens the overall process. Generally, they produce tasty and rather mineral sakes that we call “manly.”
The nansui waters like those of Shizuoka or Niigata induce slower fermentations which promote Ginjo flavours and aromas. These waters are said to produce “feminine” sake. Their silky texture makes it possible to create very dry sakes, but still with a sweet feeling. They are ideal for brewing the Niigata’s Tanrei Karakuchi sake type.