金泉（有明1号泉・有明2号泉の混合泉）Kinsen (Gold Spring — blend of Ariake No. 1 and Ariake No. 2)
Arima's signature Kinsen (Gold Spring) — a 55:37 blend of the Ariake No. 1 and No. 2 wells emerging at 81 degrees Celsius. As iron-laden water meets the air it oxidises into the famous reddish-brown turbid bath, with a sharply salty, metallic taste. At 26.13 g/kg dissolved solids and 15,470 mg/kg of chloride it is a hypersaline chloride spring exceeding ocean salinity, with iron at 46.6 mg/kg giving the rust-red coating. Heavy, mineral-coated water that leaves a thick salt veil on the skin.
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
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, netto 熱の湯).
cold sensitivity
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
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⁺7,072mgP99 national73%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺1,330mgP97 national16%
- Potassiumminor; matters for drinking limitsK⁺1,625mgP99 national10%
- LithiumLi⁺24.6mgP100 national0.8%
- Iron (II)Fe²⁺46.6mgP98 national0.4%
- MagnesiumMg²⁺13.7mgP66 national0.3%
- StrontiumSr²⁺21.2mgP97 national0.1%
- ManganeseMn²⁺8.8mgP98 national0.1%
- BariumBa²⁺15.8mgP99 national0.1%
- ZincZn²⁺0.87mgP95 national0.0%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻15,470mgP99 national99%
- BicarbonateHCO₃⁻166mgP55 national0.6%
- SulfateSO₄²⁻23.2mgP33 national0.1%
- BromideBr⁻29.5mgP95 national0.1%
- FluorideF⁻2.4mgP62 national0.0%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻0.06mgP8 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂184mgP98 national
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃94.6mgP53 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂60.9mgP73 national
- CopperCu0.0020mgP42 national
- Mercurytoxic trace — part of the drinking-safety checkHg< —mg
- Radonfaint radon — studied for joint pain (hormesis)Rn< —mg
Measured at the source
On the certificate
- Chronic gynecological conditions
- Menstrual disorders
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.
- 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.
- Takeda M et al. Hot spring bathing practices have a positive effect on mental health in Japan. Heliyon 9(9):e19631, 2023.