Yamate Onsen No. 3 is a simple thermal spring classified as hot (45.1 °C), neutral, and hypotonic. Mineralization is light at around 412 mg/kg, but the water carries a generous 105 mg/kg of metasilicic acid, leaving the kind of thin silica film that makes skin feel noticeably smoother afterwards. At the wellhead it presents as practically colorless, tasteless, and odorless — a gentle, low-stimulation entry in Beppu's hot-source roster.
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
Take care
From a certificate analyzed in 2014.
- Active stage of any illness (especially with fever)
- Active tuberculosis, advanced malignant tumor, severe anemia or other marked physical weakness
- Severe heart or lung disease causing shortness of breath on slight exertion
- Severe kidney disease with edema, gastrointestinal bleeding, visible bleeding
- Acute exacerbation of a chronic illness
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⁺82.0mgP24 national73%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺14.5mgP31 national15%
- Potassiumminor; matters for drinking limitsK⁺9.5mgP44 national5%
- Magnesiummild; a laxative if you drink itMg²⁺3.5mgP42 national5%
- LithiumLi⁺0.50mgP52 national1%
- Aluminumshows up in acidic volcanic waterAl³⁺0.06mgP33 national1%
- AmmoniumNH₄⁺0.10mgP23 national0.2%
- StrontiumSr²⁺0.10mgP24 national0.1%
- Iron (II)rusts brown in air; iron for anemia when drinkableFe²⁺< —mg
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻104mgP41 national64%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻43.7mgP39 national20%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻43.4mgP28 national16%
- FluorideF⁻0.20mgP16 national0.2%
- NitrateNO₃⁻1.7mgP90 national0.2%
- BromideBr⁻0.30mgP37 national0.1%
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃105mgP55 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂3.5mgP25 national
- Phosphoric acidH₃PO₄0.10mgP98 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂40.0mgP64 national
- LeadPb0.10mgP98 national
- ArsenicAs< —mg
- CadmiumCd< —mg
- CopperCu< —mg
Measured at the source
On the certificate
From a certificate analyzed in 2014.
- Chronic muscle or joint pain or stiffness (the chronic phase of rheumatoid arthritis, osteoarthritis, lower back pain, neuralgia, frozen shoulder, bruises, sprains and the like), muscle stiffness associated with motor paralysis, cold sensitivity, convalescence, fatigue recovery, general health improvement, reduced gastrointestinal function (heaviness, bloating), mild hypertension, impaired glucose tolerance (diabetes), mild hypercholesterolemia, mild asthma or emphysema, hemorrhoid pain, autonomic nervous system instability (sleep disorders, depressed mood), stress-related symptoms, general health improvement
- Personal hygiene for the elderly
- Autonomic nervous system instability, insomnia, depressed mood
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.