槍見の湯Yarimi no Yu Spring
A gentle simple thermal spring, sampled at the supply spout feeding the men's indoor bath at Yarimikan rather than at the wellhead. Dissolved solids come to only 0.5 g/kg, so the water is light and unassertive on the skin, and the certificate classifies it as hypotonic and neutral. What lifts it is metasilicic acid at 109.4 mg/kg — enough silica to leave the thin moisturising film that places this water in Japan's beauty-water family. Bicarbonate and chloride sit almost level in the anion table, giving a balanced, uncomplicated soak.
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⁺96.4mgP27 national81%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺13.3mgP29 national13%
- Potassiumminor; matters for drinking limitsK⁺8.4mgP42 national4%
- LithiumLi⁺0.60mgP59 national2%
- MagnesiumMg²⁺0.50mgP20 national0.8%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻165mgP54 national48%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻88.5mgP38 national45%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻10.0mgP21 national4%
- Fluoridetrace; drinking limits applyF⁻3.3mgP67 national3%
- H2PO4H₂PO₄⁻0.40mgP85 national0.1%
- BromideBr⁻0.30mgP37 national0.1%
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃109mgP58 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂4.2mgP30 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂70.7mgP73 national
- LeadPb0.0060mgP29 national
- ArsenicAs< —mg
- CadmiumCd< —mg
- ChromiumCr< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —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.
- 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.