A simple thermal spring rising at the Gyokusenkan well in Ebino (Miyazaki), neutral and hypotonic but emerging above 55 degrees Celsius. Mineralization is light at 546 mg/kg, giving a gentle, unobtrusive feel on the skin. Metasilicic acid at 110.6 mg/kg is generous for a simple spring, leaving a thin silica film that places it squarely in Japan's beauty-water family. The water shows a faint brown tint at the inlet but is otherwise odorless and tasteless.
Good for
Aches & joints
Warmth eases stiffness and raises the pain threshold. Radon and sulfate springs show the strongest evidence for joint and muscle pain.
stiff shoulders
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⁺82.7mgP26 national64%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺28.7mgP45 national25%
- Magnesiummild; a laxative if you drink itMg²⁺4.7mgP49 national7%
- Potassiumminor; matters for drinking limitsK⁺4.9mgP34 national2%
- LithiumLi⁺0.20mgP40 national0.7%
- Iron (II)Fe²⁺0.50mgP52 national0.4%
- AmmoniumNH₄⁺0.20mgP30 national0.2%
- BariumBa²⁺0.08mgP36 national
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻251mgP61 national74%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻35.7mgP36 national13%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻24.2mgP19 national12%
- FluorideF⁻0.40mgP31 national0.4%
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃111mgP59 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂2.4mgP22 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂NDmg
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂SNDmg
- ArsenicAsNDmg
- CadmiumCdNDmg
- ChromiumCrNDmg
- CopperCuNDmg
- Mercurytoxic trace — part of the drinking-safety checkHgNDmg
- LeadPbNDmg
- Radonfaint radon — studied for joint pain (hormesis)Rn—mg
Measured at the source
On the certificate
- Chronic digestive disorders
- Hemorrhoids
- Cold sensitivity
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.
- Donaubauer AJ et al. Serial radon spa therapy on pain in musculoskeletal disorders. Frontiers in Immunology, 2024.
- Verhagen AP et al. Balneotherapy for rheumatoid arthritis. Cochrane Database of Systematic Reviews CD000518, 2015.
- 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.