Oku no Yu
Analysis VerifiedA new 'Wa-modern' current emerged in Noboribetsu Onsen's history in 2006. This distinctive spring, with its faintly fragrant sulfur, evokes a sense of travel, while its chloride and sulfate composition gently infuses the skin with rich warmth. The heat gradually permeates the body's core, offering a pleasant restorative warmth that endures post-bath. It is perfectly suited for those desiring deep relaxation for mind and body in a sophisticated ambiance, far from daily clamor.
The bar length shows how abundant each component is compared to thresholds that make it "distinctive" (therapeutic spring standards, beauty spring criteria, etc.).
Undissociated boric acid with antibacterial action that keeps the skin surface clean.
The source of the distinctive sulfur smell. Dilates blood vessels via skin and inhalation to strongly boost circulation.
A natural moisturizer also used in skincare lotions. Forms a thin veil on the skin to reduce moisture loss after bathing.
- Sulfur12.6 mg/kg
- Feel
- Smells like boiled eggs; the water may turn milky white or blue-green.
- Said to
- Said to be strongly antibacterial and to promote circulation. Bathing indications include atopic dermatitis and chronic eczema.
- Note
- With sensitive skin, rinse with fresh water after bathing. Remove silver jewelry—it tarnishes.
- Chloride (salt)513 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.
- Sulfate195 mg/kg
- Feel
- Your skin feels moist; the water may taste slightly bitter.
- Said to
- Said to retain heat well and help heal cuts. Bathing indications include cuts and dry skin.
- Note
- It warms you well—do not stay in too long.
- Metasilicic acid130 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 temperature46.1℃
- 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.
This spring gushes at the elevated temperature of 46.1°C. Before entering, always rinse your hands and feet gradually with the hot water to acclimate your body to its heat. Guests with compromised cardiovascular function are advised to favor half-body immersion over full submersion.
Rich in metasilicic acid (130.3 mg/kg) and gently acidic, this sulfur spring soothes sensitive skin while addressing poor peripheral circulation and chronic cold sensitivity. The warmth penetrates deep after bathing, lingering through your body for hours. Steep yourself fully to dissolve daily stress and fatigue, unlocking profound restoration.
Those with sensitive skin or mucous membranes, and elderly guests prone to xerosis, should bathe with caution. This spring is not potable—please refrain from drinking entirely.
※ See the analysis data below for detailed contraindications
ANALYSIS DATAView all analysis fields ▼
Source Info
- Source name
- Oku no Yu
- Spring type
- 含硫黄-ナトリウム・カルシウム-塩化物・硫酸塩温泉（硫化水素型）
- Old spring type name
- 含石膏-食塩硫化水素泉
- Source temperature
- 46.1℃
- pH
- 5.7
- Flow rate
- 50 L/min
- Osmotic pressure
- 低張性
Analysis Document
- Analysis date
- 2014-10-29
- Analyst organization
- 株式会社第一岸本臨床検査センター
- Registration No.
- 北海道第12号
Cations
- Sodium ion Na⁺
- 245 mg/kg
- Potassium ion K⁺
- 74.3 mg/kg
- Ammonium ion NH₄⁺
- 1.6 mg/kg
- Magnesium ion Mg²⁺
- 19.5 mg/kg
- Calcium ion Ca²⁺
- 84.2 mg/kg
- Aluminum ion Al³⁺
- 0.20 mg/kg
- Manganese ion Mn²⁺
- 1.2 mg/kg
- Iron(II) ion Fe²⁺
- 0.40 mg/kg
- Lead ion Pb²⁺
- 0.00 mg/kg
- Cadmium ion Cd²⁺
- 0.00 mg/kg
- Total cations
- 427 mg/kg
Anions
- Fluoride ion F⁻
- 0.30 mg/kg
- Chloride ion Cl⁻
- 513 mg/kg
- Hydrogen sulfide ion HS⁻
- 0.60 mg/kg
- Thiosulfate ion S₂O₃²⁻
- 0.00 mg/kg
- Sulfate ion SO₄²⁻
- 195 mg/kg
- Bicarbonate ion HCO₃⁻
- 12.2 mg/kg
- Carbonate ion CO₃²⁻
- 0.00 mg/kg
- Hydrogen sulfate HSO₄⁻
- 0.00 mg/kg
- Dihydrogen phosphate H₂PO₄⁻
- 0.90 mg/kg
- Total anions
- 722 mg/kg
Undissociated Components
- Arsenious acid HAsO₂
- 1.2 mg/kg
- Metasilicic acid H₂SiO₃
- 130 mg/kg
- Metaboric acid HBO₂
- 64.1 mg/kg
- Total undissociated
- 196 mg/kg
Dissolved Gas
- Free carbon dioxide CO₂
- 6.8 mg/kg
- Free hydrogen sulfide H₂S
- 12.8 mg/kg
- Total dissolved gas
- 19.6 mg/kg
Totals
- Total dissolved substances
- 1344 mg/kg
- Component total
- 1364 mg/kg
- Evaporation residue
- 1241 mg/kg
Usage
- Heating
- No
- Dilution
- Yes（入浴に適した温度にするため）
- Recycle / Filter
- No
- Additives
- No
- Disinfection
- No
Indications & Contraindications
- Bathing indications
- Atopic dermatitis, Plaque psoriasis, Chronic eczema, Epidermal suppuration, 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), Severe chronic dermatitis (sulphur springs)
Drinking
- Drinkability
- Not drinkable
- Drinking notes
- Do not drink.
