草津温泉 万代鉱源泉
Kusatsu Onsen Bandaiko SourceOperated by · 御座之湯
酸
Acidic
+ Sulfate · Chloride
Hot source · 95°CUltra-acidicHigh silica
Known good for
- Skin conditionsatopic skin, eczema
- Circulationtired legs
- Aches & jointsstiff shoulders
- Sensitive-skin cautionbroken or dry skin
The Bandaiko source of Kusatsu Onsen feeds the near-side tub of Goza no Yu's Ki-no-Yu bathhouse. At pH 1.7 this is sharply acidic water — enough to prickle on contact — and it emerges at 94.6 °C, placing it among Japan's hottest natural sources, with sulfate and chloride as the dominant anions. Metasilicic acid at 528 mg/kg leaves the kind of thin silica film that makes skin feel noticeably smoother, and the bathhouse panel lists the water as documented for neuralgia, joint pain, bruises, sprains, burns, chronic digestive complaints, chronic gynecological conditions and skin condition. It is served as untreated free-flow: no dilution, no heating, no recirculation and no disinfection.
Analyzed Jul 25, 2023·（社）群馬県薬剤師会