A blended source drawing on the No. 1 and No. 2 wells of the Kinugawa-Kawaji spring development, classified as an alkaline simple thermal spring. At pH 9.1 it sits in Japan's beauty-water family, the alkalinity giving a soft, slippery feel on the skin, while a dissolved-solids total of only 447 mg/kg keeps the water light and unchallenging. The public notice posted here is written for foot bathing rather than full immersion, and records that the water is diluted, reheated to offset the cooling caused by recirculation, circulated through a filtration unit and disinfected with a chlorine agent. The same notice lists no spring-type-specific contraindications, only the standard cautions against bathing during acute illness or with irritated skin.
Good for
Smooth skin
Bicarbonate and alkalinity gently lift dead keratin while silica hydrates, leaving skin smooth. This is the basis of the beautifying-water (bijin-no-yu 美人の湯) reputation.
dry, rough skin
Recovery
Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.
fatigue, stress
Take care
- Acute illness (especially with fever)
- Active tuberculosis
- Malignant tumor
- Severe heart disease
- Respiratory failure
- Renal failure
- Bleeding disorders
- Severe anemia
- Any other illness in an actively progressing stage
Full composition
The bar is each ion's share of charge (mval%) within its group; over 20% names the spring. Gases, silica and trace metals are measured by mass only.
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺92.2mgP71 national73%
- Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺38.8mgP8 national27%
- PotassiumK⁺0.80mgP11 national0.3%
- MagnesiumMg²⁺0.10mgP11 national0.1%
- ManganeseMn²⁺0.0000mg0.0%
- Iron (II)Fe²⁺0.0000mg0.0%
- Iron (III)Fe³⁺0.0000mg0.0%
- HydrogenH⁺0.0000mg0.0%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻224mgP67 national74%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻42.2mgP25 national19%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻7.6mgP42 national4%
- Fluoridetrace; drinking limits applyF⁻1.7mgP56 national1%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻3.9mgP3 national1%
- HydroxideOH⁻0.20mgP68 national0.2%
- Hydrogen sulfideHS⁻0.20mgP36 national0.1%
- AsO2AsO₂⁻0.0000mg0.0%
- BO2BO₂⁻0.0000mg0.0%
- BromideBr⁻0.0000mg0.0%
- H2PO4H₂PO₄⁻0.0000mg0.0%
- Hydrogen phosphateHPO₄²⁻0.0000mg0.0%
- HSiO3HSiO₃⁻0.0000mg0.0%
- HSO4HSO40.0000mg0.0%
- NitriteNO₂⁻0.0000mg0.0%
- NitrateNO₃⁻0.0000mg0.0%
- PhosphatePO₄0.0000mg0.0%
- SS²⁻0.0000mg0.0%
- ThiosulfateS₂O₃²⁻0.0000mg0.0%
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃33.8mgP16 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂1.7mgP16 national
- H2SO4FreeH2SO4Free0.0000mg
- Phosphoric acidH₃PO₄0.0000mg
- Metaarsenious acidHAsO₂0.0000mg
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂0.0000mg
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S0.0000mg
- CopperCu0.03mgP94 national
- ArsenicAs0.02mgP35 national
- CadmiumCd0.0000mg
- ChromiumCr0.0000mg
- Mercurytoxic trace — part of the drinking-safety checkHg0.0000mg
- LeadPb0.0000mg
Measured at the source
Evidence
- Maeda M. 温泉の医学的効果とその科学的根拠. J. Hot Spring Science 70:197–207, 2021.
- Naito Y et al. A Hot-Spring Water Improves Inflammatory Conditions in an Atopic Dermatitis Model. Biomedicines 13(11):2707, 2025.
- Li H et al. Bicarbonate Ionized Water Bathing Enhances Natural Killer Cell Activity. Scientific Reports 14:51851, 2024.
- Takeda M et al. Hot spring bathing practices have a positive effect on mental health in Japan. Heliyon 9(9):e19631, 2023.