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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, nettō 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%)
  • Sodium4,336mgP96 national
  • Calcium443mgP91 national
  • Potassium813mgP99 national
  • Iron (II)11.4mgP89 national
  • Magnesium5.0mgP51 national
  • Ammonium0.11mgP24 national
  • Zinc1.4mgP97 national
  • Manganese2.5mgP94 national
  • Aluminum0.20mgP68 national
Anionsshare of charge (mval%)
  • Chloride7,930mgP95 national
  • Bicarbonate630mgP80 national
  • Sulfate17.0mgP31 national
  • Bromide14.8mgP90 national
  • Fluoride1.7mgP57 national
  • Iodide1.9mgP86 national
  • Hydrogen sulfide0.50mgP57 national
  • Thiosulfate0.10mgP45 national
Non-dissociatedmeasured by mass
  • Metaboric acid130mgP96 national
  • Metasilicic acid99.9mgP57 national
Dissolved gasesmeasured by mass
  • Free carbon dioxide104mgP80 national
  • Free hydrogen sulfide0.40mgP70 national
Trace metalsmeasured by mass
  • Mercury0.0009mgP54 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)

塩ChlorideSodium-Calcium Chloride spring

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, nettō 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
  • Calcium2,220mgP98 national
  • Magnesium135mgP93 national
  • Potassium204mgP97 national
  • Lithium24.5mgP99 national
  • Iron (II)41.9mgP98 national
  • Strontium31.6mgP98 national
  • Barium8.1mgP97 national
  • Copper1.1mgP100 national
Anionsshare of charge (mval%)
  • Chloride14,000mgP98 national
  • Bicarbonate505mgP75 national
  • Bromide39.3mgP97 national
  • Fluoride6.1mgP84 national
  • Iodide1.4mgP81 national
Non-dissociatedmeasured by mass
  • Metaboric acid156mgP97 national
  • Metasilicic acid38.7mgP21 national
  • Metaarsenious acid0.07mgP40 national
Dissolved gasesmeasured by mass
  • Free carbon dioxide755mgP98 national
  • Free hydrogen sulfide0.02mgP45 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 certificate:Autonomic nervous system instabilityConvalescenceFatigue recoveryGeneral health improvement

Take care

Contraindications
  • 病気の活動期（特に熱のある時）
  • 活動性の結核、進行した悪性腫瘍又は高度の貧血など身体衰弱の著しい場合
  • 少し動くと息苦しくなるような重い心臓・肺疾患
  • むくみのあるような腎不全
  • 消化管出血
  • 目に見える出血があるとき
  • 慢性の病気の急性増悪期

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
  • Calcium14.9mgP33 national
  • Potassium2.7mgP25 national
  • Magnesium0.80mgP25 national
  • Lithium0.20mgP40 national
  • Strontium0.20mgP41 national
  • Barium0.06mgP35 national
  • Aluminum< —mg
  • Manganese< —mg
Anionsshare of charge (mval%)
  • Bicarbonate86.6mgP39 national
  • Chloride37.0mgP25 national
  • Fluoride3.5mgP69 national
  • Sulfate4.1mgP15 national
  • Nitrate1.8mgP90 national
Non-dissociatedmeasured by mass
  • Metasilicic acid34.7mgP17 national
  • Metaboric acid2.0mgP19 national
Dissolved gasesmeasured by mass
  • Free carbon dioxide10.0mgP40 national
Trace metalsmeasured by mass
  • Radon2,240mgP100 national
  • Mercury0.0005mgP43 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

  • 筋肉若しくは関節の慢性的な痛み又はこわばり（関節リウマチ、変形性関節症、腰痛症、神経痛、五十肩、打撲、捻挫などの慢性期）
  • 運動麻痺における筋のこわばり
  • Cold sensitivity
  • Peripheral circulation disorders
  • 胃腸機能の低下（胃もたれ、食欲低下）
  • Mild hypertension
  • 耐糖能異常（糖尿病）
  • 軽い高コレステロール血症（脂質異常症）
  • Mild asthma or emphysema
  • Hemorrhoid pain
  • ストレスによる諸症状（睡眠障害、うつ状態）
  • 高尿酸血症（痛風）、関節リウマチ、強直性脊椎炎等（泉質別適応症）

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.