Kowakudani Onsen
Analysis VerifiedKowakidani Onsen, once known as 'Kojigoku' (Small Hell) due to its fumaroles, was renamed in 1873 following Emperor Meiji's visit. This mixed spring, combining multiple sources developed since the late Meiji era, stands as one of Hakone's most iconic hot springs. Its waters envelop the skin in a comforting salt veil, delivering restorative warmth deep into the body's core. This mellow, historically rich spring is highly recommended for those seeking deep relaxation and a profound reset from daily life.
The bar length shows how abundant each component is compared to thresholds that make it "distinctive" (therapeutic spring standards, beauty spring criteria, etc.).
A natural moisturizer also used in skincare lotions. Forms a thin veil on the skin to reduce moisture loss after bathing.
A trace component with gentle antibacterial and anti-inflammatory action.
- Chloride (salt)30.9 mg/kg
- Feel
- Tastes salty; the warmth lasts after you get out.
- Said to
- Salt is said to form a film on the skin that keeps in heat and moisture. Bathing indications include cuts, poor circulation and dry skin.
- Note
- May sting cuts. Strong salty water can tire you—avoid long soaks.
- Bicarbonate (baking soda)215 mg/kg
- Feel
- Your skin feels smooth and silky.
- Said to
- Said to remove old skin cells and excess sebum. Bathing indications include cuts, poor circulation and dry skin.
- Note
- It can leave skin dry—moisturize after bathing.
- Metasilicic acid168 mg/kg
- Feel
- Your skin may feel smoother.
- Said to
- 50 mg/kg or more is said to mark a “skin-beautifying spring”; it is also used in skincare.
- Note
- The “skin-beautifying” label is a common rule of thumb, not a legal standard.
- Source temperature60℃
- Feel
- The source is 42°C or hotter; the bath may be on the hot side.
- Said to
- Heat is said to boost circulation and warm the body.
- Note
- Older people and those with high blood pressure or heart conditions should avoid baths of 42°C or more. Keep soaks short.
Effects are general descriptions based on the Ministry of the Environment’s indications by spring type, not a guarantee.
Scores are calculated from mineral analysis data based on the Mineral Spring Analysis Guidelines (Ministry of Environment, Japan). They are unrelated to facility atmosphere or service quality.
▸Note
The temperature, pH and component values shown here are based on the hot spring analysis (source). Actual values in the bath may differ depending on heating, dilution, recycling and filtration. Please check current usage status at the facility.
The water is diluted due to the high source temperature, but avoid long soaks and stay hydrated. As a sodium-chloride spring, it warms the body deeply, and its restorative warmth lingers, making you less prone to post-bath chills. Resting after your bath is recommended.
This is a skin-friendly sodium-chloride spring with a mild alkalinity of pH 7.9. Its rich salt content forms a light veil on the skin, providing lasting restorative warmth. Furthermore, it contains 168 mg/kg of metasilicic acid, a known skin-beautifying component, which may lead to moist, silky skin after bathing.
Individuals undergoing medical treatment, who are pregnant, or have sensitive skin or mucous membranes should consult a doctor before bathing. Avoid bathing if you have acute illnesses, active tuberculosis, or severe heart disease.
※ See the analysis data below for detailed contraindications
ANALYSIS DATAView all analysis fields ▼
Source Info
- Source name
- Kowakudani Onsen
- Spring type
- Sodium Chloride Hot Spring
- Old spring type name
- 単純温泉
- Source temperature
- 60℃
- pH
- 7.9
- Osmotic pressure
- 低張性
Analysis Document
- Analysis date
- 2016-04-12
- Valid until
- 2024-04-11
- Analyst organization
- 神奈川県温泉地学研究所
- Registration No.
- 登録第1号
Cations
- Lithium ion Li⁺
- 0.02 mg/kg
- Sodium ion Na⁺
- 109 mg/kg
- Potassium ion K⁺
- 5.8 mg/kg
- Magnesium ion Mg²⁺
- 0.31 mg/kg
- Calcium ion Ca²⁺
- 7.4 mg/kg
- Aluminum ion Al³⁺
- 0.01 mg/kg
- Manganese ion Mn²⁺
- 0.08 mg/kg
- Iron(II) ion Fe²⁺
- 0.02 mg/kg
- Zinc ion Zn²⁺
- 0.00 mg/kg
- Strontium ion Sr²⁺
- 0.03 mg/kg
- Copper ion Cu²⁺
- 0.00 mg/kg
- Total cations
- 123 mg/kg
Anions
- Fluoride ion F⁻
- 0.09 mg/kg
- Chloride ion Cl⁻
- 30.9 mg/kg
- Sulfate ion SO₄²⁻
- 48.3 mg/kg
- Bicarbonate ion HCO₃⁻
- 215 mg/kg
- Carbonate ion CO₃²⁻
- 1.3 mg/kg
- Bromide ion Br⁻
- 0.05 mg/kg
- Nitrate ion NO₃⁻
- 0.00 mg/kg
- Metasilicate ion SiO₃²⁻
- 2.6 mg/kg
- Metaborate ion BO₂⁻
- 0.15 mg/kg
- Total anions
- 298 mg/kg
Undissociated Components
- Metasilicic acid H₂SiO₃
- 168 mg/kg
- Metaboric acid HBO₂
- 3.0 mg/kg
- Total undissociated
- 171 mg/kg
Dissolved Gas
- Free carbon dioxide CO₂
- 4.5 mg/kg
- Free hydrogen sulfide H₂S
- 0.00 mg/kg
- Total dissolved gas
- 4.5 mg/kg
Totals
- Total dissolved substances
- 592 mg/kg
- Component total
- 597 mg/kg
- Evaporation residue
- 483 mg/kg
Usage
- Heating
- Yes（The water is heated for hygiene purposes as it is stored in a holding tank.）
- Dilution
- Yes（Water is added because the source temperature is high.）
- Recycle / Filter
- No
- Additives
- No
- Disinfection
- No
Indications & Contraindications
- Bathing indications
- Cuts and grazes, Peripheral circulatory failure, Poor circulation, Depression, Xeroderma
- General indications
- High blood pressure (mild), Rheumatoid arthritis, Autonomic instability, Insomnia, Chronic pain or stiffness in muscles and joints, Muscle stiffness due to motor paralysis, Gastrointestinal dysfunction
- Contraindications
- Acute illness (especially with fever), Active tuberculosis, Malignant tumors, Severe heart disease, Respiratory failure, Renal failure, Bleeding disorders, Severe anemia, Any actively progressing illness, Pregnancy (especially early and late stages)
Drinking
- Drinkability
- Not drinkable
