Hakone-Yumoto Onsen (Suimeiso)
Analysis UnverifiedHakone-Yumoto is said to date back to the Nara period, the oldest of Hakone's seven historic spas. In the Edo period it thrived as a healing stop for travelers on the Tokaido, nestled by the forest of Sounji Temple, linked to the Hojo clan. This source rises at 45.2°C as an alkaline simple spring of pH 8.5, its softly balanced water wrapping the skin in smoothness. Gentle enough for all ages, it is a spring that unwinds city fatigue at the gateway to Hakone.
The bar length shows how abundant each component is compared to thresholds that make it "distinctive" (therapeutic spring standards, beauty spring criteria, etc.).
A trace component with gentle antibacterial and anti-inflammatory action.
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 alkaline pH 8.5 water gently removes skin oils, so moisturize afterward. As a mild simple spring, it suits a slow soak around 42°C, mixing in half-body bathing to warm up at leisure.
Soft on the skin at pH 8.5 and carrying 70.6 mg/kg of metasilicic acid, this water may support a smoother skin feel. A leisurely soak in this mild simple spring invites deep relaxation for body and mind.
Avoid bathing with fever or active illness, or serious heart, lung or kidney disease. Do not bathe after drinking or right before or after meals; older people and those with high blood pressure should avoid baths of 42°C or hotter.
※ See the analysis data below for detailed contraindications
ANALYSIS DATAView all analysis fields ▼
Source Info
- Source name
- Hakone-Yumoto Onsen (Suimeiso)
- Spring type
- Alkaline Simple Hot Spring
- Old spring type name
- 単純温泉
- Source temperature
- 45.2℃
- pH
- 8.5
- Osmotic pressure
- 低張性
Analysis Document
- Analysis date
- 2025-02-25
- Analyst organization
- 神奈川県温泉地学研究所
- Registration No.
- 神奈川県知事登録第1号
Cations
- Lithium ion Li⁺
- 0.02 mg/kg
- Sodium ion Na⁺
- 148 mg/kg
- Potassium ion K⁺
- 2.2 mg/kg
- Ammonium ion NH₄⁺
- 0.00 mg/kg
- Magnesium ion Mg²⁺
- 0.22 mg/kg
- Calcium ion Ca²⁺
- 21.6 mg/kg
- Aluminum ion Al³⁺
- 0.01 mg/kg
- Manganese ion Mn²⁺
- 0.00 mg/kg
- Iron(II) ion Fe²⁺
- 0.06 mg/kg
- Zinc ion Zn²⁺
- 0.00 mg/kg
- Lead ion Pb²⁺
- 0.00 mg/kg
- Strontium ion Sr²⁺
- 0.03 mg/kg
- Copper ion Cu²⁺
- 0.00 mg/kg
- Cadmium ion Cd²⁺
- 0.00 mg/kg
- Total cations
- 0.17 mg/kg
Anions
- Fluoride ion F⁻
- 0.22 mg/kg
- Chloride ion Cl⁻
- 167 mg/kg
- Sulfate ion SO₄²⁻
- 83.3 mg/kg
- Bicarbonate ion HCO₃⁻
- 69.1 mg/kg
- Carbonate ion CO₃²⁻
- 1.7 mg/kg
- Bromide ion Br⁻
- 0.37 mg/kg
- Nitrate ion NO₃⁻
- 2.3 mg/kg
- Hydrogen metasilicate HSiO₃⁻
- 4.4 mg/kg
- Metaborate ion BO₂⁻
- 1.2 mg/kg
- Total anions
- 0.33 mg/kg
Undissociated Components
- Metasilicic acid H₂SiO₃
- 70.6 mg/kg
- Metaboric acid HBO₂
- 6.4 mg/kg
- Total undissociated
- 0.08 mg/kg
Dissolved Gas
- Free carbon dioxide CO₂
- 0.36 mg/kg
Totals
- Component total
- 0.58 mg/kg
Usage
- Heating
- No
- Dilution
- No
- Recycle / Filter
- No
- Additives
- No
- Disinfection
- No
Indications & Contraindications
- Bathing indications
- Autonomic instability, Insomnia, Depression
- General indications
- High blood pressure (mild), Rheumatoid arthritis, 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
