A sodium-calcium chloride spring carrying sulfur, salty and heat-retaining in character. At the wellhead its pH of 10.0 makes it strongly alkaline, giving the pronounced slippery feel of Japan's beauty-water family. It carries hydrogen sulfide, so a faint rotten-egg note and a light salty tang come through at the source. A cold-mineral-leaning low-temperature spring (33 C at source), it is reheated for bathing.
Good for
Warming
Salt forms a film on the skin that slows heat loss, so the warmth lingers long after the bath (the classic heat-keeping water, nettō 熱の湯).
cold sensitivity
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
Cuts
Mineral-rich chloride, sulfate and sulfur waters have a long-recorded soothing effect on minor cuts and slow-healing skin.
minor wounds
Recovery
Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.
fatigue, stress
Take care
- see attached panel
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.
- Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺425mgP72 national79%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺97.9mgP73 national21%
- PotassiumK⁺2.7mgP25 national0.3%
- AmmoniumNH₄⁺0.10mgP24 national0.2%
- MagnesiumMg²⁺0.10mgP11 national0.0%
- BariumBa²⁺0.10mgP53 national0.0%
- StrontiumSr²⁺0.10mgP26 national0.0%
- AluminumAl³⁺0.0000mg0.0%
- Iron (II)Fe²⁺0.0000mg0.0%
- Iron (III)Fe³⁺0.0000mg0.0%
- HydrogenH⁺0.0000mg0.0%
- LithiumLi⁺0.0000mg0.0%
- ManganeseMn²⁺0.0000mg0.0%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻775mgP79 national93%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻18.6mgP65 national3%
- HSiO3HSiO₃⁻41.1mgP84 national2%
- SulfateSO₄²⁻6.7mgP17 national0.6%
- Hydrogen sulfideHS⁻4.3mgP89 national0.6%
- BO2BO₂⁻4.8mgP80 national0.5%
- FluorideF⁻1.8mgP56 national0.4%
- HydroxideOH⁻1.6mgP92 national0.4%
- BromideBr⁻2.5mgP74 national0.1%
- BicarbonateHCO₃⁻60.0mgP32 national0.0%
- IodideI⁻0.30mgP62 national0.0%
- ThiosulfateS₂O₃²⁻0.10mgP45 national0.0%
- Hydrogen phosphateHPO₄²⁻0.0000mg0.0%
- HSO4HSO40.0000mg0.0%
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃0.0000mg
- Phosphoric acidH₃PO₄0.0000mg
- Metaarsenious acidHAsO₂0.0000mg
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂0.0000mg
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂0.0000mg
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S0.0000mg
- ArsenicAs< —mg
- CadmiumCd< —mg
- CopperCu< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —mg
- LeadPb< —mg
Measured at the source
On the certificate
- see attached panel
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.
- Kario K et al. Hemodynamic Effects of Hot Spring Bathing. Hypertension Research 46(3):711–720, 2023.
- 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.