🧪 Annex Science Series Vol.2｜What is super soft water? The science of “softness” created by a hardness of 1.7

The true identity of “soft water” is “hardness”

The “hardness” of water is mainly caused by **calcium (Ca)andIt is determined by the magnesium (Mg)** content (=hardness).
The World Health Organization (WHO) classification is as follows:

Hot spring water 99 hardness: 1.7 mg/L
This value is extremely low even in the “soft water” range;super soft waterIt is classified as
Because Ca and Mg are very low,Mild taste and no metallic tasteThis can be explained scientifically.

“Natural low hardness” brought by the Shirasu Plateau

The water sampling area, Tarumi City, Kagoshima Prefecture, originates from volcanic activity.Shirasu Plateau (volcanic glassy porous layer)It is an area where
This layer contains metal ions (Ca²⁺, Mg²⁺, etc.)Natural filter that easily absorbsfulfills the role of
Therefore, the hardness component naturally decreases as groundwater passes through it.
Extremely low Ca/Mg = low hardness water qualityis born.

🔬 scientific points
・Low hardness = less Ca and Mg → less bitterness and astringency
・Natural filtration of whitebait layer → Low hardness remains stable for a long time

Soft water and hard water: the difference in how they feel on your body

Both soft and hard water are safe drinking water.
Physiologically, the rate of water absorption isOsmolarity, temperature, gastric contentsIt is determined by the hardness, and there is almost no difference depending on the hardness.
However, hard water may irritate the stomach and intestines depending on the person.
Soft water is less irritating;Soft in the mouth and easy to drinkIt is said that
Therefore,Easy to accept for infants and the elderlyThere are practical advantages.

The science of cooking and extraction: Soft water brings out the flavor of the ingredients

• tea/coffee: Due to low Ca and Mg, precipitation with tannins and excessive astringency are suppressed,Easy to smell。

• Cooking rice: Starch gelatinization progresses more evenly than hard water,Plump and shinyFinished in

• Dashi/Soup:Mineral interference is small,Clear flavorIt can be extracted to

These characteristics have been reported by the Japanese Society of Culinary Science, etc.Research results on water hardness and cooking propertiesIt is also consistent with
Super soft water with a hardness of 1.7 / Hot spring water 99It can be said that it is a logical water for both home cooking and professional cooking.

Comparison with water around the world (typical hardness)

The water of Tarumi in Kagoshima is rare in the world.extremely low hardness waterand
The unique character of “gentle water” is scientifically supported.

“Gentleness” proven by hardness of 1.7

• Hardness = Ca/Mg content. Hot spring water 991.7 mg/Lsuper soft water.

• Low hardness is achieved through natural filtration on the Shirasu Plateau.

• Easy to drink, and makes the most of the ingredients in cooking and extraction.

• The uniqueness of Onsen Water 99 is that it is scientifically backed "friendly water".

"Onsen Water 99 Annex Science Series" provides factual and easy-to-understand explanations about the science, quality, and safety of water.