Water hardness

Hardness is an index of the concentration of calcium ions and magnesium ions in water, and it is mainly used to indicate how hard or soft the water is. Water is broadly classified as hard or soft: the higher the hardness value, the harder the water, and the lower the value, the softer. Hardness is expressed in mg/L (milligrams per liter), and the value ranges are as follows. - Soft water: 3 or less - Moderately soft water: 3 to 6 - Slightly hard water: 6 to 8 - Moderately hard water: 8 to 14 - Hard water: 14 to 20 - Very hard water: 20 or more Methods of measuring hardness include German hardness (dH) and American hardness (ppm). German hardness is the amount of calcium and magnesium contained in 100 ml of water, converted to calcium carbonate, and 1 dH is equivalent to approximately 17.8 ppm. Differences in hardness affect both the production and the flavor of sake, so it is a very important factor in sake brewing. The process of turning hard water into soft water is called "softening" (軟化), and it makes it possible to adjust the flavor and mouthfeel.