A sodium-led bicarbonate spring — the classic jūsō-sen style — drawn from the No. 2 well of Settsukyo Hana-no-Sato Onsen in Takatsuki. Alkaline and slippery on the skin, and carrying a generous load of metasilicic acid, it sits squarely in Japan's beauty-water family. The surveyors noted a faint hydrogen sulfide note and bubbles rising at the wellhead. The certificate states the water is served undiluted but reheated to bathing temperature, then recirculated and chlorine-disinfected for hygiene.
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
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⁺331mgP65 national99%
- CalciumCa²⁺0.90mgP2 national0.3%
- PotassiumK⁺1.3mgP15 national0.2%
- AmmoniumNH₄⁺0.20mgP30 national0.1%
- AluminumAl³⁺0.10mgP54 national0.1%
- LithiumLi⁺0.10mgP28 national0.1%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻589mgP80 national67%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻66.7mgP95 national15%
- Fluoridetrace; drinking limits applyF⁻30.4mgP100 national11%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻31.6mgP22 national6%
- SulfateSO₄²⁻2.7mgP12 national0.4%
- Hydrogen sulfideHS⁻0.50mgP55 national0.1%
- HydroxideOH⁻0.20mgP66 national0.1%
- Hydrogen phosphateHPO₄²⁻0.10mgP33 national0.0%
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃90.4mgP51 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂25.5mgP78 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S0.50mgP72 national
- ArsenicAs< —mg
- CadmiumCd< —mg
- ChromiumCr< —mg
- CopperCu< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —mg
- LeadPb< —mg
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.