Naruto Onsen
Analysis UnverifiedDrilled at Naruto in Ajigasawa's Maito district, Naruto Onsen is described as "fossil seawater": ancient sea brine trapped underground long ago. With more than 21 g of dissolved minerals per kilogram, the pale-yellow water tastes intensely salty with a hint of bitterness, much like the sea itself. The Naruto source leaves a fine film of salt on the skin, so its warmth lingers long after the bath, making it a natural companion for anyone thawing out beside the winter Sea of Japan.
The bar length shows how abundant each component is compared to thresholds that make it "distinctive" (therapeutic spring standards, beauty spring criteria, etc.).
Salinity comparable to seawater. The salt film traps heat for outstanding warmth ("hot bath spring").
Salt forms a thin film on the skin, retaining heat after bathing. Helps with poor circulation.
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.
This hypertonic strong salt spring is very concentrated, so start with 5-10 minute soaks and rest in between. Those with sensitive skin may want to rinse lightly with fresh water afterward.
With 12,377 mg/kg of chloride and 21.304 g/kg of total solutes, the salt left on the skin slows the evaporation of sweat, offering restorative warmth that lasts. On cold days or when shoulders and back feel stiff, it may help relieve pain.
Long soaks in this hypertonic strong salt spring can cause fatigue; rinse sensitive skin afterward, and avoid bathing during acute illness or with serious heart or kidney conditions.
※ See the analysis data below for detailed contraindications
ANALYSIS DATAView all analysis fields ▼
Source Info
- Source name
- Naruto Onsen
- Spring type
- Sodium Chloride strong saline Spring
- Source temperature
- 37.6℃
- pH
- 7.4
- Flow type
- 動力揚湯
- Osmotic pressure
- 高張性
Analysis Document
- Analysis date
- 2025-07-16
- Analyst organization
- 環境保全株式会社
- Registration No.
- 青森県第3号
Cations
- Lithium ion Li⁺
- 0.10 mg/kg
- Sodium ion Na⁺
- 7776 mg/kg
- Potassium ion K⁺
- 440 mg/kg
- Ammonium ion NH₄⁺
- 7.9 mg/kg
- Magnesium ion Mg²⁺
- 5.1 mg/kg
- Calcium ion Ca²⁺
- 232 mg/kg
- Aluminum ion Al³⁺
- < 0.05 mg/kg
- Manganese ion Mn²⁺
- 0.10 mg/kg
- Iron(II) ion Fe²⁺
- 0.20 mg/kg
- Zinc ion Zn²⁺
- < 0.005 mg/kg
- Lead ion Pb²⁺
- < 0.002 mg/kg
- Copper ion Cu²⁺
- < 0.005 mg/kg
- Cadmium ion Cd²⁺
- < 0.001 mg/kg
- Total cations
- 8.5 mg/kg
Anions
- Fluoride ion F⁻
- 0.80 mg/kg
- Chloride ion Cl⁻
- 12377 mg/kg
- Thiosulfate ion S₂O₃²⁻
- < 0.1 mg/kg
- Sulfate ion SO₄²⁻
- 40.0 mg/kg
- Bicarbonate ion HCO₃⁻
- 214 mg/kg
- Carbonate ion CO₃²⁻
- < 0.1 mg/kg
- Bromide ion Br⁻
- 41.0 mg/kg
- Iodide ion I⁻
- 2.4 mg/kg
- Nitrite ion NO₂⁻
- < 0.1 mg/kg
- Nitrate ion NO₃⁻
- < 0.1 mg/kg
- Hydrogen phosphate HPO₄²⁻
- < 0.1 mg/kg
- Total anions
- 12.7 mg/kg
Undissociated Components
- Arsenious acid HAsO₂
- 0.00 mg/kg
- Metasilicic acid H₂SiO₃
- 112 mg/kg
- Metaboric acid HBO₂
- 29.8 mg/kg
- Total undissociated
- 0.14 mg/kg
Dissolved Gas
- Free carbon dioxide CO₂
- 24.5 mg/kg
- Total dissolved gas
- 0.02 mg/kg
Totals
- Total dissolved substances
- 21.3 mg/kg
- Component total
- 21.3 mg/kg
- Evaporation residue
- 21.0 mg/kg
Usage
- Heating
- Yes
- Dilution
- No
- Recycle / Filter
- Recycled / Filtered
- Additives
- No
- Disinfection
- Yes
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
