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Ryokan Hanamusubi

Water profile

Ryokan Hanamusubi

Spring chemistry and what it does, with the research behind it.

極楽泉源Gokuraku Spring

塩ChlorideSodium Chloride spring

A scorching 98 °C sodium chloride source, neutral in pH but richly mineralized at 14.4 g/kg dissolved solids — the kind of body that leaves a salty mineral film on the skin and holds heat long after the soak. Clear at the wellhead, it oxidises into a brown sediment on standing and carries the salty, iron-tinged 'kinki' character that defines Arima's gold-spring tradition. Among Japan's hottest natural sources.

Good for

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

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

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.

Cationsshare of charge (mval%)
  • Sodium4,336mgP97 national
  • Calcium443mgP92 national
  • Potassium813mgP99 national
  • Iron (II)11.4mgP90 national
  • Magnesium5.0mgP51 national
  • Ammonium0.11mgP23 national
  • Zinc1.4mgP97 national
  • Manganese2.5mgP93 national
  • Aluminum0.20mgP65 national
Anionsshare of charge (mval%)
  • Chloride7,930mgP96 national
  • Bicarbonate630mgP81 national
  • Sulfate17.0mgP30 national
  • Bromide14.8mgP92 national
  • Fluoride1.7mgP56 national
  • Iodide1.9mgP88 national
  • Hydrogen sulfide0.50mgP55 national
  • Thiosulfate0.10mgP42 national
Non-dissociatedmeasured by mass
  • Metaboric acid130mgP97 national
  • Metasilicic acid99.9mgP54 national
Dissolved gasesmeasured by mass
  • Free carbon dioxide104mgP80 national
  • Free hydrogen sulfide0.40mgP68 national
Trace metalsmeasured by mass
  • Mercury0.0009mgP64 national
  • Arsenic< —mg
  • Cadmium< —mg
  • Copper< —mg
  • Lead< —mg

Measured at the source

Source temperature
98.1°C
Hot
Tonicity
14.44g/kg
Hypertonic
Free CO₂
104mg/kg
Low
Free H₂S
0.40mg/kg
Low

Evidence

  1. 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.
  2. Kario K et al. Hemodynamic Effects of Hot Spring Bathing. Hypertension Research 46(3):711–720, 2023.
  3. Naito Y et al. A Hot-Spring Water Improves Inflammatory Conditions in an Atopic Dermatitis Model. Biomedicines 13(11):2707, 2025.
  4. Donaubauer AJ et al. Serial radon spa therapy on pain in musculoskeletal disorders. Frontiers in Immunology, 2024.
  5. Verhagen AP et al. Balneotherapy for rheumatoid arthritis. Cochrane Database of Systematic Reviews CD000518, 2015.
  6. Takeda M et al. Hot spring bathing practices have a positive effect on mental health in Japan. Heliyon 9(9):e19631, 2023.

大沢源泉（神戸市北区大沢町上大沢井尻7-8番）Osawa Spring (Kita-ku, Kobe, Osawa-cho 7-8)

鉄Iron-bearingSodium-Calcium Chloride spring · +Chloride

An iron-rich sodium-calcium chloride brine — a strong-salt spring of the iron-bearing family. Dissolved solids reach 24 g/kg with chloride near 14,000 mg/kg, and Fe(II) at 41.9 mg/kg oxidises into the trademark reddish-brown sediment on contact with air. Clear from the wellhead but markedly salty and bitter on the tongue with the iron-tinged 'kinki' note, then weakly acidic and cool (28 °C) — a cold mineral source heated for bathing.

Good for

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.

Cationsshare of charge (mval%)
  • Sodium6,070mgP98 national
  • Calcium2,220mgP99 national
  • Magnesium135mgP94 national
  • Potassium204mgP98 national
  • Lithium24.5mgP100 national
  • Iron (II)41.9mgP98 national
  • Strontium31.6mgP98 national
  • Barium8.1mgP97 national
  • Copper1.1mgP100 national
Anionsshare of charge (mval%)
  • Chloride14,000mgP98 national
  • Bicarbonate505mgP77 national
  • Bromide39.3mgP98 national
  • Fluoride6.1mgP81 national
  • Iodide1.4mgP85 national
Non-dissociatedmeasured by mass
  • Metaboric acid156mgP98 national
  • Metasilicic acid38.7mgP20 national
  • Metaarsenious acid0.07mgP36 national
Dissolved gasesmeasured by mass
  • Free carbon dioxide755mgP98 national
  • Free hydrogen sulfide0.02mgP50 national
Trace metalsmeasured by mass
  • Mercury< —mg

Measured at the source

Source temperature
28.5°C
Low temp.
Tonicity
24.20g/kg
Hypertonic
Free CO₂
755mg/kg
Typical
Free H₂S
0.02mg/kg
Low

Evidence

  1. 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.
  2. Kario K et al. Hemodynamic Effects of Hot Spring Bathing. Hypertension Research 46(3):711–720, 2023.
  3. Naito Y et al. A Hot-Spring Water Improves Inflammatory Conditions in an Atopic Dermatitis Model. Biomedicines 13(11):2707, 2025.
  4. Takeda M et al. Hot spring bathing practices have a positive effect on mental health in Japan. Heliyon 9(9):e19631, 2023.

神鉄有馬ラジウム鉱泉Shintetsu Arima Radium Spring

ラRadonSodium-Calcium Bicarbonate-Chloride spring

An exceptionally radon-rich simple radioactive cold-mineral spring — 2,240 Bq/kg places it far above the standard radon-spring threshold. Welling up at 20.3 °C by natural flow, the water is colourless, clear, tasteless and odourless, with only 0.25 g/kg dissolved solids — gentle in body, characteristic of the 'hormesis' radium-spring tradition. Heated before bathing as a cold-mineral source.

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

Recovery

Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.

fatigue, stress

On the 2015 certificate:Autonomic nervous system instabilityConvalescenceFatigue recoveryGeneral health improvement

Take care

Contraindications

From a certificate analyzed in 2015.

  • 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
  • Renal failure 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.

Cationsshare of charge (mval%)
  • Sodium46.3mgP12 national
  • Calcium14.9mgP32 national
  • Potassium2.7mgP25 national
  • Magnesium0.80mgP24 national
  • Lithium0.20mgP37 national
  • Strontium0.20mgP41 national
  • Barium0.06mgP32 national
  • Aluminum< —mg
  • Manganese< —mg
Anionsshare of charge (mval%)
  • Bicarbonate86.6mgP41 national
  • Chloride37.0mgP23 national
  • Fluoride3.5mgP68 national
  • Sulfate4.1mgP14 national
  • Nitrate1.8mgP91 national
Non-dissociatedmeasured by mass
  • Metasilicic acid34.7mgP16 national
  • Metaboric acid2.0mgP18 national
Dissolved gasesmeasured by mass
  • Free carbon dioxide10.0mgP40 national
Trace metalsmeasured by mass
  • Radon2,240mgP100 national
  • Mercury0.0005mgP48 national
  • Copper< —mg

Measured at the source

Source temperature
20.3°C
Cold mineral
Tonicity
0.25g/kg
Hypotonic
Flow rate
59L/min
Typical
Free CO₂
10mg/kg
Low
Radon
2240Bq/kg
High

On the certificate

From a certificate analyzed in 2015.

  • 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
  • Peripheral circulation disorders
  • Reduced gastrointestinal function (heaviness, poor appetite)
  • Mild hypertension
  • Impaired glucose tolerance (diabetes)
  • Mild hypercholesterolemia (dyslipidemia)
  • Mild asthma or emphysema
  • Hemorrhoid pain
  • Stress-related symptoms (sleep disorders, depressed mood)
  • Hyperuricemia (gout), rheumatoid arthritis, ankylosing spondylitis and the like (spring-type indications)

Evidence

  1. 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.
  2. Donaubauer AJ et al. Serial radon spa therapy on pain in musculoskeletal disorders. Frontiers in Immunology, 2024.
  3. Verhagen AP et al. Balneotherapy for rheumatoid arthritis. Cochrane Database of Systematic Reviews CD000518, 2015.
  4. Takeda M et al. Hot spring bathing practices have a positive effect on mental health in Japan. Heliyon 9(9):e19631, 2023.

Educational, not medical advice. If you have a health condition, consult a physician before onsen therapy.